751 10 13249 https://digitalcollections.lakeheadu.ca/files/original/3e37d66ea2ef94f7247b2b9f29a8d1f2.pdf 0f119cb53f0e214bb5fdf701eef07ec8 PDF Text Text _.,, -Volume 5 Spring Issue March 2010 Greetings Everyone, I am so thrilled that at this coming spring convocation (May 2010) we shall see a record number of possibly 47 NASL Diploma graduates. Isn't this exciting news! I want to encourage each potential graduate to complete all assignments by April 1, 2010. Call our office or email Diane or myself if you need assistance. The registration forms for all years are coming in quite quickly now, so please send in yours if you have not. We still want to use paper registration so our office has access to number of students so we can decide how many classes we are going to schedule. You are able to start registering online now from home or work, if you required assistance phone me at 807-343-8003 or Diane at 807-3438542. To check the dates for the summer courses for 2010, see page 4. The N.L.I.P. faculty lecturers are returning and so are the elders, Ron and Gloria. If you would like to contribute any information to the next newsletter, email Diane at dmayee@lakeheadu.ca or call her. Gidaa miigwechiwendam ekashkitooyan chi anishinaabemoyan (Be thankful you can speak your Native Language) Kichi Miigwech, Charlotte Neckoway Native Language Instructors' Program Lakehead University, 955 Oliver Road Thunder Bay, ON P7B 5E1 IA Message from tbe Principal Good Day to all Teachers, Don't forget to bring your lessons and visual aids that you have already done in your classroom, for those that are not teaching to begin writing their lesson plans and making visual aids. July is coming around and before we know it we are all meeting and having to do what we do best; teaching and speaking our Native languages. Also please don't forget to start asking your students what are the main slang words/sayings. E.g. cool man, high five and so on. Write them out in your Native language and we will share them in our classes in July See you all there in July, Meegwetch, Florrie Inside this Issue: Message from your Coordinator and Principal 1 Upcoming Conferences 2 Recipes 3 2010 Spring and Summer Courses, Language books 4 Native Crafts-Hoop Drums and Arrowhead Necklace 5 Joke Page 6 �I C t! .!C Antshinnnbomowtn An ond Ortuno Anlsh1naobo�n Ro?Ourco Oovak>pmont Amshlnn.nbomowfn Storie� on<I Musk: AddJo ond Stop Oonce Nl!)hl Sc.holarthrp Award.sand Bnnquot OorfUc Storlighl. Puppor En1orto1nor Anrshloaat>omowfn BlllQO Fun Night P,ooorv;-iUon l1111L,ttvoG Ch11drnn's Activttlos Fonst ond Socml Cmlt WOfkahops Country and Wostom MurJc Youth WorkShops ones Evening Socials l:cJucnlkm and t loallh Work.a.hops Roolstor for tho Conforonco .:md hoar Anlshlnnabomowln for 4 doysl 0 (.) ·E- D) C 8a. :, The web site for the 17th Annual Stabilizing Indigenous Languages Sympo­ sium "Indigenous Languages Across the Generations - "Language and Place" to be held June 25-27, 2010 at University of Oregon - Eugene, Oregon, USA is now accessible at http://www.uoregon.edu/~nwili/SILS/SILS.html The 6th Giving the Gift of Language Symposium and Workshop on Native Lan­ guage Instruction and Acquisition held on April 17-19, 2010, is now accessi­ ble at http://www.nsilc.org/private/GTOL1.htm Native Language Instructors' Program Newsletter Page 2 �_... Cook me up a VeciPe! ........................................................................................•..••••..................................... ...._,, ' Ingredients Directions Calabacitas (Skillet Squash} 5 cubed small summer squash 1 diced large onion 2 roasted peeled green pep­ pers or 1 small can diced green pep­ pers 1 tablespoon shortening or oil 3/4 cup shredded longhorn cheese Saute onion in shortening or oil until soft. Add squash and stir until almost tender. Add peppers; simmer briefly. Sprinkle on cheese and stir until melted. From: Dove Yield: 5 servings 7. Drain and eat like hamburgers. Chicken and Ramps with Sweet Potatoes Ingredients 2 tbsp olive oil 2 tsp chopped fresh sage 2 tbsp Dijon mustard 2 tsp grated lemon rind 2 tsp chili powder 4 boneless, skinless, chicken breasts salt and freshly ground pepper 2 sweet potatoes cut into I inch cubes 4 ramps or 2 leeks, white and light green part only, sliced I cup chicken stock 2 tbsp balsamic vinegar Directions Preheat oven to 400F Combine I tbsp olive oil, sage, mustard, lemon rind, and chili. Reserve I tbsp of mixture, and brush the rest over the chicken breasts. Season with salt and pepper. Heat remaining I tbsp oil in a large oven proof skillet over medium heat. Add chicken breasts, and cook 2 minutes per side or until browned. Remove from skillet and toss in sweet pota­ toes. Saute for I minute, add ramps or leeks and saute for 2 minutes. Add stock, reserved mustard mixture and balsamic vinegar and bring to a boil. Reduce heat, return chicken breasts to skillet and place over vegetables. Cover skillet. Place in oven and bake for 15 to 20 minutes, or until chicken juices run clear. Slice chicken breasts and serve over vegetables. Drizzle over the pan liquid . •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• Grilled: Lemon, Butter, \Vorcester­ shire Planked Salmon Ingredients 4 salmon 6-8 oz fillets, about I inch thick, skin-on I cedar plank, soaked under water for at least I hour Lemon-Pepper dry seasoning I /3 cup melted butter or margarine 1/3 cup fresh lemon juice I /3 cup Worcestershire sauce 24 drops Tabasco sauce Basting Sauce: Melt butter in a sauce pan on low heat, add lemon juice1 Worcestershire sauce, and Tabasco ana heat through. Seasoning: Sprinkle fillets on all sides with lemon­ pepper dry seasoning pressing the season- i�fo the nesh and place in the refrigerator for 30 minutes. Directions Preheat grill to medium low heat, about 350 degrees, place soaked plank on grill rack, close lid, and heat for 3 minutes. Using tongs, nip plank and place salmon skin side down on heated side of plank. Baste fillets with prepared sauce. Close lid and grill for 12-15 minutes until done and salmon is opaque in the center and nakes easily with a fork. Baste a few times with basting sauce during cooking. Remove plank and salmon from the grill and serve. Garnish with lemon wedges, and goes well with sides of broccoli and parsley boiled new potatoes. Page 3 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• �Job hunting hmmmmmm? Maybe this can help........ Various teaching positions may be found online. Those who are looking for positions in language and for those who are interested in teaching in First Nations may want to check out the following link. www.jobsineducation.com or www.educationcanada.com Fantastic teaching resources incorporating Native language can be found at these sites: http://snow.utoronto.ca/index.php?option=com-content&task =v1ew&id=24&Itemid=33 http://www.native-languages.org/ojibwe_animals.htm http://www.nativetech.org/games/index.php Native Language Institute courses offered for summer term 2010 r------------------------------------------------· Institute courses for 2010 NL 2713 - Algonquian Linguistics NL 3813 - Special Topics II Native Language Teacher Certification (NLTC) 2010 July 5-30, 2010 lnstitute/Y ear 4 July 12-30, 2010 Ojibwe OJI 1013 Pan I July 5-22, 2010 OJI 1015 Part II July 26 - August 12, 2010 Cree Language Resources Intermediate Ojibwe Advance Ojibwe Introductory Ojibway (Severn) ISBN: 88800002873 Publisher: Lu Printer ISBN: 88800003687 Author: Beardy ISBN: 88800000826 Author: Beardy, Tom Price: $69.95 Price: $69.95 Price: $69.95 Cree Legends & Narratives From West Coat ISBN: 0887 5 51599 Author: Ellis, C. Douglas Price: $56.25 Ninootaan I can Hear It ISBN: 0921064144 Author: O'Meara Price: $34.95 Please visit the Lakehead Bookstore website for information about the books they have in stock, at http://bookstore.lakeheadu.ca Page 4 �_.. e Materials: Hoop Di-um • A round metal cookie tin • A can opener • Self-sticking shelf paper • Scissors, a pencil and ruler • A piece of leather large enough to fit over the top of the cookie tin • A knife • 2.5 meters (8 ft.) of leather lace Directions: Have an adult remove the bottom of the cookie tin with the can opener. f Cut a piece of shelf paper the same circumference and width as the tin. Peel of the backing and stick the paper on the tin. Trace a circle about 2.5 cm ( I -inch) bigger than the tin. Cut out the circle. Mark 12 evenly spaced dots around the edge of the rough side of the leather, about 2.5 cm (I -inch) in from the edge. Use the knife to carefully poke holes in the leather at these dots. Cut the leather lace into six equal pieces. Soak the laces and the leather circle in warm water for about 15 minutes, until they soften. Take the laces and leather out of the water and pat them dry. Thread a lace through one of the holes in the leather. Double knot the lace, leaving a length hanging. Place the cookie tin on the center of the leather on the rough side. Stretch the lace across the bot1om of the drnm and thread it up through the hole that is across from where the lace is tied. Pull it tight and double knot it. Thread and tie the next three laces the same way, pulling the leather tight but being careful not to tear it. As you pull the last two laces across the bottom of the drum, wrap them around the other laces where they cross in the center. Tie the laces tightly. Set the drum in a wann place to dry for a few days. As the leather dries, it will shrink and tighten. •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• An-owheac\ Necklace Use actual stone arrowheads to make a Native American necklace. You need: • • • Stone Arrowhead 30" Suede Cord Pony Beads Instructions: Wrap a 30" piece of suede around the arrowhead cross crossing as shown in the photo. Tie in the back. Push both ends of the cord through a pony bead. You'll need to cut the ends to a point to get them to fit through. Push the bead down to the arrowhead. Slide three more pony beads on each side. Tie ends together. Trim. Page 5 �COLD\\ INTER! The Blackfeet asked their Chief in autumn, if the winter was going to be cold or not. Not really knowing the an­ swer, the chief replies that the winter was going to be cold and that the members of the village were to collect wood to be prepared. Being a good leader, he then went to the nearest phone booth and called the National Weather Service and asked, "Is this winter to be cold?" The man on the phone responded, "This winter was going to be quite cold indeed." So the Chief went back to speed up his people to collect even more wood to be prepared. A week later he called the National Weather Service again, "Is it going to be a very cold winter?" "Yes," the man re­ plied, "its going to be a very cold winter." So the Chief goes back to his people and orders them to go and find every scrap of wood they can find. Two weeks later he calls the National Weather Service again and asks "Are you absolutely sure, that the winter is going to be very cold?" "Absolutely" the man replies, "the Blackfeet are collecting wood like crazy!" Dry Bones STRANGE WHITE I/EN TN AN./Y CLOTHES Pl.ANTING CROPS?! TIE ARST THAM<SGMNG "Youj11.�t sl,o,v 11p here i/legt1f�r t111d expect m to tell you 11bo11t com?" DON BURNSTICK JOKES YOU MIGHT BE A REDSKIN IF YOU> you have blankets for curtains ... your dogs look like their going on a hunger strike... you have more than 5 cars and only one of them works ... and that's only in the summer, because in the winter, its too cold for II to start up you use ketchup and water to fill your bingo dabber... you use a close hanger for a car antenna... your cars only alarm is the sound of it opening up a mile away and the hunger struck dog inside.... you can fit 16 Indians in a ford pickup or a Honda... you go swimming in your underwear .. . you go to AA meetings just for coffee... you hide your money in your sock, don't hide it in your bra, it'll be found anyway you go to KFC to celebrate thanksgiving you use your sons hockey bag for a bingo bag you bank at the money mart you ever skinned road kill.... "oh look at that deer...oh.... uh ... we'll come back when its dark you ever shot a deer or a moose inside your house "hey .... what is that... ... honey, bring me my .22!!!" the most confusing day in your community is fathers day ... you can properly execute the red river gig with rubber boots on .... if you carry a five gallon jug and a cut up garden hose in the trunk of your car... if you try to make dry meat out of baloney... if your pocket knife has ever been display as "exhibit A your honor" you use your probation officer as a reference... if your screen door has no screen on it... if people can hear your car long before they can see it... you been kicked out of several rehab centers for snagging... you met your current spouse in a AA rehab... your toolbox consists of duck tape and a butter knife... Page 6 � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Anishinaabemowik - Indigenous Languages Program Historical Documents Creator An entity primarily responsible for making the resource Faculty of Education, Native Language Instructors Program Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Native Language Instructor's Program Newsletter Vol 5 (Spring Issue) March 2010 Subject The topic of the resource Universities Description An account of the resource Native Language Instructor Program Faculty of Education Lakehead University Creator An entity primarily responsible for making the resource Native Language Instructor Program Date A point or period of time associated with an event in the lifecycle of the resource 2009-03-01 Rights Information about rights held in and over the resource Faculty of Education, Lakehead University Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English Type The nature or genre of the resource Text https://digitalcollections.lakeheadu.ca/files/original/e3c61b41a70507fde9996cd617f8254c.pdf 5c6ea3ce1c186fe3f505a7f6cb70f3e2 PDF Text Text January 2012 Newsletter Message from the NLIP Coordinator Bruce K. Beardy Booshoo, Waachiye, Aniin to all of you. Welcome to the latest issue of the NLIP newsletter. We are doing our best to offer two issues of the NLIP newsletter annually that will be submitted to you, NLIP students, electronically. In each issue, you will find information pertaining to Native Languages and Native Language Education. Feel free to pass it on to others. The past 2011 NLIP Summer School was a success and it was great to see many people achieve their goals. In the fall of 2011, I have been busy attending conferences and doing some research for Native Languages Immersion programming. I participated in an Indigenous Languages Institute symposium entitled "Immersion for all Environments" in Albuquerque, NM. It was a two day conference discussing the Native language immersion programs and its successes across Canada and the United States. A lot of networking resulted from this gathering. I also had an opportunity to visit an Immersion school in the state of Arizona while I was in the area. The Tse'hootsooi Dine' Bi'olta' is a Navajo immersion school located in Fort Defiance, Arizona. I felt very welcomed by the administration and staff of the school. I observed in classrooms and briefly spoke to teaching staff. It was so wonderful to see and hear the children speak in their Native language and many of them wearing their traditional Navajo clothing. More recently, I visited the Niigaane Ojibwe Immersion School at Leech Lake Indian Reservation in Minnesota. This visit was to do some research and get an idea how the immersion school operates and its' function, the role of the teachers and the community. I also attended the "Circle of Light - Learning Together for Student Success" conference in Toronto. This is a First Nation, Metis and Inuit Education conference put on jointly by Aboriginal Affairs and Northern Development and Ministry of Education. Approximately 1000 participants attended this conference. While at this conference, the Chair of the Aboriginal Education Department and I met with Ontario College of Teachers representatives to discuss some of the issues NLIP students have told us about. It was a very positive and productive meeting and we hope this will alleviate some obstacles that you are facing. We will continue to work with OCT and resolve the issues that we experience. .....Continues on page 2 ' · 'Ii • { A 'IP". � _.,1 ........., �...continued from page 1 Lakehead University, Aboriginal Education Department also co­ hosted with the Ontario College of Teachers a "Conversation Circles to Support the Development of Additional Qualification Guidelines for Teaching First Nations Students". There were approximately 30 participants of Ojibwe and Oji-Cree speakers at this gathering. Out of this conversations, teaching immersion Native languages was a big topic. The Cree speakers held their own conversations in their territory with OCT. We are hoping to offer a course Teaching Native Language Immersion to our NLIP students for 2012 summer. This course will fall under the NLIP Summer Institute program and is designed for Native Language teachers who have completed the NLTC or the NASL Diploma programs. For more information, you can call me directly at 1-807-343-8003 or e­ mail: bbeardy@lakeheadu.ca. We feel it Is Important to remind people of the description of the Native Language Instructors' Program (NLIP), Its objectives and other programs. 1. 2. 3. 4. 5, 6. 7. 8. Description of the Program The Native Language Instructors' Program (NLIP) at Lakehead University is the only program in Ontario with a mandate from the Ontario College of Teachers to provide teacher certification in Algonquian languages. Established in 1984, the purpose of NLIP is to provide persons who are fluent in their native language with a recognized (in accordance with the Ministry of Education) means of teaching that language to their respective communities. In other words, NLIP serves largely as a school that educates students in a relatively standardized method of instruction, which is applied to traditional languages. By no means restrictive, NLIP provides a learning environment that respects, encompasses and promotes traditional teaching practices and beliefs. NLIP also provides courses to those persons who wish to become fluent in a particular language. Students for the Native Language Instructors' program apply from across Ontario and other regions; once accepted they have an opportunity to earn a teaching certificate or diploma. The program is offered in the month of July for three or four summers. The purpose of the Native Language Instructors' Program is to increase the number of Native language teachers through summer programs, which will prepare them to teach Native Languages as described in Ontario Ministry of Education regulations. The program provides the students the study of the structure of the Native language, pedagogical principles, methods and techniques for teaching Native Languages. Course requirements are met through a combination of courses and student teaching. the students will have understanding of the underlying structure of their language and will have developed literacy skills; the �udents will have a knowledge of methods and techniques for teaching Native As A Second Language; the students will have an understanding of practical pedagogical principles that will help them work within the context of the school, with administrators, teachers, students, and the community; the students will successfully complete a combination of observation and teaching experience; the students will have gained knowledge of the traditional teachings and values inherent in Native languages and culture; to maintain the survival of the Native language and culture; that the NLIP students have outlined for them the traits, skills and habits of a successful university student; that the NLIP students be trained in and measured by a single teaching formula and a common lesson planning and evaluation format; that NUP provide to its students the means to develop traits, skills and habits of a successful university !s'tlldent. Anishinaabemowin Gikino'amaadiiwigamig �Native Language Teacher's Certification A three summer program for the month of July; training in teaching Native as a second language to students whose first language is English. The Certification Program is designed for individuals who want to teach a Native Language as a second language in a primary or secondary school. It focuses on developing skills required for second language teaching. The curriculum is designed for students who enter the program with an Algonquian Language background. Admission to the NLTC Program Students will be admitted to the program provided that they meet both of the following: (a) Native language requirement of the course to which the candidate wishes to be admitted. i.e. for both NASL/NLTC - fluently speak a native language. (b) Lakehead University Admission Requirements. Requirements for Admission to Undergraduate Degree Programs (See Mature Student and Extraordinary Admissions in the Lakehead University on-line calendar at www.lakeheadu.ca). Components In order to qualify for the Transitional Certificate of Qualification and Registration through the Ontario College of Teachers (OCT), a student will be required to complete successfully each year all four half-courses of the following: 1. Algonquian Courses: Introduction to literacy in Native Language, Practice in reading and writing, curriculum materials and understanding of language structures. 2. Methodology Courses: Methods of second language teaching, planning, use of curriculum guidelines, classroom activities, evaluation, and materials production. 3. Pedagogy Courses: A survey of teacher ethics, classroom management skills, record keeping and planning. An examination of characteristics of children. Identification and solutions to common problems facing Native language teachers. An examination of bilingual education, strengths, weaknesses, problems, and opportunities. 4. Practicum: Students become familiar with Ministry of Education documents, plan for instruction, classroom observation and on-site teaching experiences in Native language classes with children aged five to sixteen. Students participate in workshops and assemblies that provide activities and resources for the classroom. Anishinaabemowin Gikino'amaadiiwigamig �- --- �-- ----�---- Native as a Second Language for Non-fluent Speakers NLTC student graduates wishing to enter the fourth year of the NASL diploma may do so providing that they complete all the NLIP requirements. NASL on-campus courses consists of: Algonquian 2233, Education 1354, and Education 1574. Education 1599 is a supervised fall and winter practicum, off-campus, in the fourth year of the Native Language Instructors' Program and is a required course to complete six prescribed assignments. Upon successful completion of the Fourth Year or NASL Program, student is awarded a Lakehead University Native as a Second Language Diploma and can attend the Lakehead University Convocation. Each summer, two Advanced Native Language and/or Linguistic courses are offered to students who have graduated from both NLTC and NASL programs wishing to extend their knowledge and do research in the area of their specialty as well as to any person similarly qualified. For 2012 NLIP Summer Session these courses are being offered: Native language 2711 Introduction to Native American linguistics A survey of the native languages of North America: present situation, historical relationships, sound systems, grammatical structures, geographic and social variation, writing systems and language maintenance. The basic principles of descriptive and historical linguistics will be introduced. Native language 3811 Special Topic I A half course on a selected topic. (Possibly an Immersion course.) The courses in this series are intended for students who wish to learn either Ojibwe or Cree, and are not normally intended for students already fluent in one of these languages. These Ojibwe and Cree courses are usually offered through-out the year including spring and summer and depending on the student enrollment. Some of these courses are cross listed with Indigenous Learning. Ojibwe as a Second Language Lakehead University offers introductory courses in two of the main dialect variants found in Ontario. Severn Ojibwe (sometimes also referred to as 'Oji-Cree,' and as Anihshininiimowin in the language itself) is the primary dialect spoken in much of Ontario north of the Berens River. It is frequently written using the traditional syllabic writing system; a wide variety of orthographic traditions, both alphabetic and syllabic, are used in Ojibwe dialects. Western Ojibwe refers to the dialects of Ojibwe spoken in communities from approximately Sault Ste. Marie in the east, along the north shore of Lake Superior, and through the Lake of the Woods area. Severn Ojibwe Courses include: Introduction to Severn Ojibwe Part I and Part II. Intermediate Ojibwe Advanced Ojibwe Western Ojibwe Courses include: Introduction to Western Ojibwe Part I and Part II. Cree as a Second Language Introduction to Cree Part I and Part II are normally offered through out the year but is dependent on the student enrollment. �The Native Language Minor Students at Lakehead University may obtain a Minor in Native Languages by taking an appropriate series of courses. NLIP Linguistic Community Residence A) The first is intended for fluent speakers of a Native language (usually Ojibwe or Cree). With the cooperation of the Lakehead University Residence and Conference Services, townhouses for NLIP students are set a side for the month of July each summer. The residence provides atmosphere conducive to serious study and encourages the use of the Native language to the greatest extent. Parents are responsible for children in the residence community and on campus. B) The second is intended for individuals who wish to learn a Native language, or to improve their fluency in a Native language. NLIP Residence Coordinator and Assistant are available to provide services day and evenings including weekends on­ site at the residence. An overall average of 60% is required in three courses chosen in consultation with the Coordinator, NLIP program. NLIP Elders Program There are two paths for obtaining the Native Language Minor. Program Requirements for Fluent Speakers The following sequence of courses is recommended for �tudents who are fluent in Ojibwe or Cree. 1) The equivalent of ONE full first year" ALGO" course. This requirement may be satisfied by taking ALGO 1212 and ALGO 1232 (Note: these courses are normally offered during the summer session only). 2) The equivalent of TWO full courses beyond the first year level. This may be met by taking a combination of"ALGO" courses and/or" NALA" courses. In consultation with the NLIP coordinator, special combinations of courses may be designed. Program Requirements for Second Language Learners and Non-Fluent Speakers The following sequence of courses is recommended for students who are learning Ojibwe or Cree. 1) The equivalent of ONE full first year"OJIB" or "CREE" course. This requirement is satisfied by taking OJIB 1013 or 1014 and OJIB 1015 or 1016 or Cree 1010 and Cree 1012. These courses are regularly offered during the fall and winter semesters, and may also be offered during the month of July. 2) The equivalent of TWO full courses beyond the first year level. This may be met by taking a combination of"OJIB" or"CREE" courses and/or appropriate "NALA" courses. In consultation with the NLIP coordinator, special combinations of courses may be designed. Elders provide counselling and general support to students regarding personal, social, guidance and cultural needs. On occasion, Elders are invited by the faculty lecturers and children's programs to share storytelling sessions and cultural knowledge and experiences to the classes. They conduct opening and closing prayers at assemblies and staff meetings, smudges, sweat lodge, and sunrise ceremonies. They maintain liaison and communication with the students, children's programs, faculty and staff. Elders are available during the day and in the evenings including weekends for the students. NLIP Student Support Workers The student support workers provide assistance and support to students in accessing University services: Aboriginal Services, Library, Learning Assistance Centre, Health Services, Financial Aid Office, etc. They also support students regarding personal, social and cultural needs. Maintain liaison and communication with the students, children's programs, faculty and staff and work with NLIP student council regarding goals and activities. They encourage students to participate in the planning and organization of activities, maintaining communication links, scheduling and advertising of events. Aboriginal Education Counsellor may be available on-site, three days per week to provide social, cultural and academic support to students during the summer programs. �Lakehead University Native Language Teacher's Certification (NLTC) July 3 - July 27, 2012 Native as a Second Language (NASL) Diploma July 9 - July 27, 2012 Institute Courses July 9 - July 27, 2012 Native Language 2 711 Introduction to Native American Linguistics A survey of the Native languages of North America: present situation, historical relationships, sound systems, grammatical structures, geographic and social variation, writing systems and language maintenance. The basic principles of descriptive and historical linguistics will be introduced. Native Language 3811 Special Topic I A half course on a selected topic. (Possibly an Immersion course.) Second Language Courses Ojibwe July 3 - July 19, 2012 Ojibwe 1013 Part I Introduction to basic Severn Ojibwe phonetics, grammar and conversation. July 23 - August 9, 2012 Ojibwe 1015 Part II Developmental of conversational skills and practice in writing. Cree July 3 - July 19, 2012 Cree 1010 Part I Introduction to basic Severn Ojibwe phonetics, grammar and conversation. July 23 - August 9, 2012 Cree 1012 Part II Developmental of conversational skills and practice in writing. �™� Ani$hinaabemowin-Teg Inc. Presents 0 March 28th to April 1, 2012 l<Gw�dln C�1tno ;md Convctntlon Centre Saull St•. M,uht, Mich,tffan R�lttrotlon f.1,&,,,dOo.odt,,.,•-­ Dotc_, IS 2'0111<: V$Ot m•oo .a«n ,,oo 1'!000 E-..:�• 0 00 �'l'o./11 This is a Drug and Alcohol Free Event Please Koop Conforoncc Aroa Smoke F roe $t-nd l'•1mitnt .end ff�••trJtton to 0t•tr-.iN- C tunJ fc:unc:t� •H.....,, S61, P o na 1"Ch� 011 POP IC.0 f•• ,�, lf7-64at morv lnformotlon phNISV vmoll Nortlna Osowomldc ot mortl1<1omlk@hotm"Gll.com or Jonis Fairbanks ot foirbonksj hotmoil.com or check out oor wetbsltv www.ateg.<<1 for ... 19th Annual Stablllzlng Indigenous Languages Symposium Thompson Rivers University, Kamloops, British Columbia, Canada, May 17-19, 2012 For more information contact Jack Miller at JamiUer@tru.ca Click here to see Tim on youtube: Tjm speaks Ojibwe[Tim ojibwemo http:/Jwww.tr:.u.ca/sils,'1tml �New Release Are you returning for NLIP 20 12 Summer School? If you were an NLTC (Year 1 , 2 and 3) student last summer, you may proceed to register on-line for the NLTC summer courses. Year 3 NLTC students who wish to do an additional year for year 4 or NASL Diploma program may also proceed to register on-line. Since many of you were able to register your courses on-line last year, this should be a little bit more easier. If you are unsure which courses you should register, please refer to your transcripts. The "ALGO" year 1 and 2 courses are a bit tricky as you will need to know which section of the ALGO course you took last year and must register the same section for second year students, i.e. for Cree speakers you took ALGO 1 21 2 AC and can register for ALGO 1 232 AC; for western Oji-Cree speakers; ALGO 1 21 2 AA for 1 232 AA; eastern Ojibwe speakers AB; and for western speakers AD. For returning first year NLTC students, ALGO 1 232 AA/AD sections of Western Ojibwe and Western Oji-Cree may be combined for the 201 2 Summer session as is the first year ALGO 1 21 2 AA/AD sections. All others, new first year NLTC applicants and Institute Courses applicants MUST apply through Lakehead ADMISSIONS office. If you require assistance or need more information, call Diane Maybee or Bruce K. Beardy at 1 -807-343-8542 or 1 -807-343-8003; E-mail: dma bee@lakeheadu.ca or bbeardy@lakeheadu.ca. Nenapohs Legends Memoir 2 Margaret Cote ISBN: 978-0-88977-219-9 Series: University of Regina Publications 25 Year: 2011 Pages: 1 1 2 Binding: Paperback $19.95 Seven traditional stories of the Saulteaux trickster. Nenapohs. In both Standard Roman Orthography and Syllabics, with English translation and a glossary of Saulteaux words. Shop on-line at WWW.CPRCPRESS.CA For returning NLTC students, using your Mylnfo (WebAdvisor) go to htt!UL howtoregister.lakeheadu.ca/ for registration instructions. PLEASE read and follow the instructions. If you are having a difficult time, call Diane or Bruce at the NLIP office. Bring your Lesson Plans The summer NLIP Practicum Planner is encouraging all returning NLTC students to bring their Lesson Plans that they used for their classes over the school year. Please review your lessons carefully and identify what worked best and how they can be improved. Bring all, if you have available, your worksheets, exemplars and rubrics that go with the lessons. With this idea, you will have all your resources to use for your practice teaching next summer. You will be required to teach a minimum of three practicums during the summer. For Ontario Ministry of Education Native Languages resources, visit the website at: hUp://www._edu_.gov.on.caLeng/ For Ontario College of Teachers, visit the website at: b_ttp;//�o_ct.ca/ � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Anishinaabemowik - Indigenous Languages Program Historical Documents Creator An entity primarily responsible for making the resource Faculty of Education, Native Language Instructors Program Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Native Language Instructor's Program Newsletter January 2012 Subject The topic of the resource Universities Description An account of the resource Native Language Instructor Program, Faculty of Education, Lakehead University. This newsletter was sent to students (current and future), and faculty and staff. Creator An entity primarily responsible for making the resource Native Language Instructor Program Faculty of Education Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 2012-01-01 Rights Information about rights held in and over the resource Faculty of Education, Lakehead University Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English Type The nature or genre of the resource Text https://digitalcollections.lakeheadu.ca/files/original/8154f0af057b119dd8208a23f584961e.pdf f4397eb22cabad582e48970a6ebf2063 PDF Text Text 69th ANNUAL MEETING Eau Claire, Wisconsin — April 24-25, 2023 INSTITUTE ON LAKE SUPERIOR GEOLOGY Part 1 — Program and Abstracts �Thank you to our sponsors! A SPECIAL THANK YOU TO OUR INDIVIDUAL CONTRIBUTORS: FREDERICK CAMPBELL, VAL CHANDLER, JIM DEGRAFF, THOMAS ERICKSON, TOM FITZ, DAVE GOOD, PAULA LEIER-ENGELHARDT, ALLAN MACTAVISH, BOB MAHIN, GORDON MEDARIS JR., JIM MILLER, STEVEN PINTA, TOD ROUSH, AND GERRY WHITE i �Proceedings of the 69th ILSG Annual Meeting – Part 1 69th ANNUAL MEETING INSTITUTE ON LAKE SUPERIOR GEOLOGY April 24-25th Eau Claire, Wisconsin HOSTED BY Rob Lodge, Esther Stewart, Carsyn Ames Co-Chairs University of Wisconsin- Eau Claire and Wisconsin Geological and Natural History Survey Proceedings - Volume 69 Part 1 – Program and Abstracts Compiled and edited by Carsyn Ames Cover Photos. Left— Photograph showing a group of men, women and children traveling through a forest north of Chippewa Falls, Wisconsin in a horse-drawn carriage, Chippewa Co., 1916. Center— Cross-bedding in basal Cambrian sandstone Eau Claire Co., 1919. Right — Outcrops of rhyolite schist along the north fork of the Eau Claire River, Eau Claire Co. 1919. ii �Proceedings of the 69th ILSG Annual Meeting – Part 1 69th INSTITUTE ON LAKE SUPERIOR GEOLOGY VOLUME 69 CONSISTS OF: PART 1: PROGRAM AND ABSTRACTS PART 2: FIELD T RIP GUIDEBOOK Trip 1: PRECAMBRIAN GEOLOGY OF THE CHIPPEWA RIVER VALLEY Trip 2: WISCONSIN’S PALEOZOIC STRATIGRAPHY AND TOUR OF CRYSTAL CAVE Trip 3: PRECAMBRIAN GEOLOGY OF THE EAU CLAIRE RIVER VALLEY Trip 4: QUATERNARY GEOLOGY AND GEOMORPHOLOGY OF THE EAU CLAIRE REGION Reference to material in Part 1 should follow the example below: Grauch, V.J.S., Heller, Sam J., Stewart, Esther K., and Woodruff, Laurel G. 2023. Exploring the geology of the Midcontinent Rift under western Lake Superior using a preliminary velocity model of seismic line GLIMPCE C. in Ames C. (Ed.), Institute on Lake Superior Geology Proceedings, 69th Annual Meeting, Eau Claire, Wisconsin, Part 1 - Abstracts and Proceedings. v.69, part 1, p.3738. Published by the 69th Institute on Lake Superior Geology and distributed by the ILSG Secretary: Pete Hollings - ILSG Secretary Department of Geology Lakehead University 955 Oliver Road Thunder Bay, ON P7B 5E1 Canada Email: peter.hollings@lakeheadu.ca ILSG website: www.lakesuperiorgeology.org iii �Proceedings of the 69th ILSG Annual Meeting – Part 1 ISSN 1042-9964 Part 1: Program and Abstracts Table of Contents Institutes on Lake Superior Geology, 1955-2023 v Sam Goldich and the Goldich Medal vii Goldich Medal Guidelines ix Goldich Medalists and Goldich Medal Committee xi Citation for Goldich Medal Award to Peter Hollings xii Honoring the Pioneers of Lake Superior Geology xii Nomination for Thomas Benton Brooks, Pioneer of Lake Superior Geology xv Memoriams for Stephen Allard, Steven Hauck and Manfred Kehlenbeck xx Eisenbrey Student Travel Awards xxv Joe Mancuso Student Research Awards xxvi Doug Duskin Student Paper Awards and Award Committee xxvii Board of Directors and Session Chairs xxviii Field Trip Leaders and Guidebook Authors xxix Report of the 68th Annual Meeting xxx Technical Program xxxiv Poster Presentations xl Banquet Presentation xliii Abstracts 1-99 iv �Proceedings of the 69th ILSG Annual Meeting – Part 1 Institutes on Lake Superior Geology, 1955-2023 # Date Place Chairs 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 Minneapolis, Minnesota Houghton, Michigan East Lansing, Michigan Duluth, Minnesota Minneapolis, Minnesota Madison, Wisconsin Port Arthur, Ontario Houghton, Michigan Duluth, Minnesota Ishpeming, Michigan St. Paul, Minnesota Sault Ste. Marie, Michigan East Lansing, Michigan Superior, Wisconsin Oshkosh, Wisconsin Thunder Bay, Ontario Duluth, Minnesota Houghton, Michigan Madison, Wisconsin Sault Ste. Marie, Ontario Marquette, Michigan St. Paul, Minnesota Thunder Bay, Ontario C.E. Dutton A.K. Snelgrove B.T. Sandefur R.W. Marsden G.M. Schwartz & C. Craddock E.N. Cameron E.G. Pye A.K. Snelgrove H. Lepp A.T. Broderick P.K. Sims & R.K. Hogberg R.W. White W.J. Hinze A.B. Dickas G.L. LaBerge M.W. Bartley & E. Mercy D.M. Davidson J. Kalliokoski M.E. Ostrom P.E. Giblin J.D. Hughes M. Walton M.M. Kehlenbeck v �Proceedings of the 69th ILSG Annual Meeting – Part 1 # 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Date 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Place Milwaukee, Wisconsin Duluth, Minnesota Eau Claire, Wisconsin East Lansing, Michigan International Falls, Minnesota Houghton, Michigan Wausau, Wisconsin Kenora, Ontario Wisconsin Rapids, Wisconsin Wawa, Ontario Marquette, Michigan Duluth, Minnesota Thunder Bay, Ontario Eau Claire, Wisconsin Hurley, Wisconsin Eveleth, Minnesota Houghton, Michigan Marathon, Ontario Cable, Wisconsin Sudbury, Ontario Minneapolis, Minnesota Marquette, Michigan Thunder Bay, Ontario Madison, Wisconsin Kenora, Ontario Iron Mountain, Michigan Duluth, Minnesota Nipigon, Ontario Sault Ste. Marie, Ontario Lutsen, Minnesota Marquette, Michigan Ely, Minnesota International Falls, Minnesota 57 58 59 60 61 62 63 64 65 66 67 68 69 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 Ashland, Wisconsin Thunder Bay, Ontario Houghton, Michigan Hibbing, Minnesota Dryden, Ontario Duluth, Minnesota Wawa, Ontario Iron Mountain, Michigan Terrace Bay, Ontario Meeting cancelled Virtual meeting Sudbury, Ontario Eau Claire, Wisconsin vi Chairs G. Mursky D.M. Davidson P.E. Myers W.C. Cambray D.L. Southwick T.J. Bornhorst G.L. LaBerge C.E. Blackburn J.K. Greenberg E.D. Frey & R.P. Sage J. S. Klasner J.C. Green M.M. Kehlenbeck P.E. Myers A.B. Dickas D.L. Southwick T.J. Bornhorst M.C. Smyk L.G. Woodruff R.P. Sage & W. Meyer J.D. Miller & M.A. Jirsa T.J. Bornhorst & R.S. Regis S.A. Kissin & P. Fralick M.G. Mudrey & Jr., B.A. Brown P. Hinz & R.C. Beard L. Woodruff & W.F. Cannon S. Hauck & M. Severson M. Smyk & P. Hollings A. Wilson & R. Sage L. Woodruff & J. Miller T.J. Bornhorst & J. Klasner J. Miller, G. Hudak, D. Peterson M. Jirsa, P. Hollings & T. Boerboom, P. Hinz & M.Smyk T. Fitz P. Hollings T.J. Bornhorst & A. Blaske J. Miller & M. Jirsa R. Cundari & P. Hinz J. Miller, C. Schardt & D. Peterson A. Pace, A. Wilson & T.J. Bornhorst L. Woodruff, W. Cannon & E.K. Stewart P. Hollings & M.C. Smyk Cancelled by the COVID-19 pandemic M. Jirsa, M. Smyk & P. Hollings R.M. Easton & W. Bleeker R. Lodge, E.K. Stewart, & C. Ames �Proceedings of the 69th ILSG Annual Meeting – Part 1 Sam Goldich and the Goldich Medal Sam Goldich received an A.B. from the University of Minnesota in 1929, a M.A. from Syracuse University in 1930, and a Ph.D. from the University of Minnesota in 1936. During World War II Sam worked for the U.S. Geological Survey in mineral exploration. In 1948, Sam returned to the University of Minnesota, and became Professor and Director of the Rock Analysis Laboratory the following year. He rejoined the U.S. Geological Survey in 1959 and was appointed as the first Branch Chief of the Branch of Isotope Geology. Sam returned to academia in 1964 when he went to Pennsylvania State University. He left PSU in 1965 and moved to the State University of New York at Stony Brook, where he stayed for 3 years. Restless yet again, he moved to Northern Illinois University in 1968 where he was a professor until his retirement in 1977. Sam’s final move was to Denver where he became an emeritus at the Colorado School of Mines. Sam died in 2000, less than a month before his 92nd birthday. In the late 1970s, Geological Society of America Special Paper 182, which included seminal geochronological studies by Sam Goldich and coworkers on the Archean rocks of the Minnesota River Valley, was nearing completion. At this time various ILSG regulars began discussing the possibility of recognizing Sam for his pioneering work on the resolution of age relationships and thus the geology of Precambrian rocks in the Lake Superior region. Three members, R.W. Ojakangas, J.O. Kalliokoski and G.B. Morey, presented the idea to the ILSG Board of Directors in 1978. The Board approved the creation of an award, provided funding could be obtained. It was suggested that collecting one or two dollars at registration for a dedicated account would provide resources for striking the medal. A general request was made to the ILSG membership for donations and Sam himself offered a challenge grant to match the contributions. In total $4,000 was collected and thus began the work of creating the Goldich Medal. The initial Goldich Award was presented to Sam by G.B. Morey in 1979 and consisted of a large paper proclamation. For the actual medal, G.B. Morey consulted with the foundry on production details, while Dick Ojakangas and Jorma Kalliokoski worked on the design of the award, suggesting that it be given for “outstanding contributions to the geology of the Lake Superior region.” Simultaneously, a committee of J.O. Kalliokosi, W.F. Cannon, M.M Kehlenbeck, G.B. Morey, and G. Mursky developed the Award Guidelines that were approved by the ILSG Board. By 1981 all the elements of the Goldich Award had come together, and the second recipient, Carl E. Dutton, Jr., received the Goldich Medal for 50 years of significant contributions to the understanding of the geology of the Lake Superior region. Since the beginning, the Awards Committee has consisted of individuals representing industry, government and academia, with each member of the Committee serving for three years. The medal is now awarded every year at the annual ILSG meeting. Reference: Morey, G.B. and Hanson, G.N. (editors). 1980. Selected studies of Archean gneisses and Lower Proterozoic rocks, southern Canadian Shield. Geological Society of America, Special Paper 182, 175 p. Prepared by various Goldich Medal Awardees, 2007 vii �Proceedings of the 69th ILSG Annual Meeting – Part 1 INSTITUTE ON LAKE SUPERIOR GEOLOGY GOLDICH MEDAL viii �Proceedings of the 69th ILSG Annual Meeting – Part 1 Goldich Medal Guidelines (Adopted by the Board of Directors, 1981; amended 1999) Preamble The Institute on Lake Superior Geology was born in 1955, as documented by the fact that the 27th annual meeting was held in 1981. The Institute’s continuing objectives are to deal with those aspects of geology that are related geographically to Lake Superior; to encourage the discussion of subjects and sponsoring field trips that will bring together geologists from academia, government surveys, and industry; and to maintain an informal but highly effective mode of operation. During the course of its existence, the membership of the Institute (that is, those geologists who indicate an interest in the objectives of the ILSG by attending) has become aware of the fact that certain of their colleagues have made particularly noteworthy and meritorious contributions to the understanding of Lake Superior geology and mineral deposits. The first award was made by ILSG to Sam Goldich in 1979 for his many contributions to the geology of the region extending over about 50 years. Subsequent medallists and this year’s recipient are listed in the table below. Award Guidelines 1) The medal shall be awarded annually by the ILSG Board of Directors to a geologist whose name is associated with a substantial interest in, and contribution to, the geology of the Lake Superior region. 2) The Board of Directors shall appoint the Goldich Medal Committee. The initial appointment will be of three members, one to serve for three years, one for two years, and one for one year. The member with the briefest incumbency shall be chair of the Nominating Committee. After the first year, the Board of Directors shall appoint at each spring meeting one new member who will serve for three years. In his/her third year this member shall be the chair. The Committee membership should reflect the main fields of interest and geographic distribution of ILSG membership. The out-going, senior member of the Board of Directors shall act as liaison between the Board and the Committee for a period of one year. 3) By the end of November, the Goldich Medal Committee shall make its recommendation to the Chair of the Board of Directors, who will then inform the Board of the nominee. 4) The Board of Directors normally will accept the nominee of the Committee, inform the medallist, and have one medal engraved appropriately for presentation at the next meeting of the Institute. 5) It is recommended that the Institute set aside annually from whatever sources, such funds as will be required to support the continuing costs of this award. ix �Proceedings of the 69th ILSG Annual Meeting – Part 1 Nominating Procedures 1) The deadline for nominations is November 1. Nominations shall be taken at any time by the Goldich Medal Committee. Committee members may themselves nominate candidates; however, Board members may not solicit for or support individual nominees. 2) Nominations must be in writing and supported by appropriate documentation such as letters of recommendation, lists of publications, curriculum vita’s, and evidence of contributions to Lake Superior geology and to the Institute. 3) Nominations are not restricted to Institute attendees, but are open to anyone who has worked on and contributed to the understanding of Lake Superior geology. Selection Guidelines 1) Nominees are to be evaluated on the basis of their contributions to Lake Superior geology (sensu lato) including: a) importance of relevant publications; b) promotion of discovery and utilization of natural resources; c) contributions to understanding of the natural history and environment of the region; d) generation of new ideas and concepts; and e) contributions to the training and education of geoscientists and the public. 2) Nominees are to be evaluated on their contributions to the Institute as demonstrated by attendance at Institute meetings, presentation of talks and posters, and service on Institute boards, committees, and field trips. 3) The relative weights given to each of the foregoing criteria must remain flexible and at the discretion of the Committee members. 4) There are several points to be considered by the Goldich Medal Committee: a) An attempt should be made to maintain a balance of medal recipients from each of the three estates—industry, academia, and government. b) It must be noted that industry geoscientists are at a disadvantage in that much of their work in not published. 5) Lake Superior has two sides, one the U.S., and the other Canada. This is undoubtedly one of the Institute’s great strengths and should be nurtured by equitable recognition of excellence in both countries. x �Proceedings of the 69th ILSG Annual Meeting – Part 1 Goldich Medalists 1979 Samuel S. Goldich 1998 Zell Peterman 2016 Mark A. Jirsa 1980 not awarded 1999 Tsu-Ming Han 2017 Philip Fralick 1981 Carl E. Dutton, Jr 2000 John C. Green 1982 Ralph W. Marsden 2001 John S. Klasner 2018 Val W. Chandler 2019 Mark Severson 1983 Burton Boyum 2002 Ernest K. Lehmann 2020 not awarded 1984 Richard W. Ojakangas 2003 Klaus J. Schulz 2021 Alan MacTavish 1985 Paul K. Sims 2004 Paul Weiblen 2022 Terrence J. Boerboom 1986 G.B. Morey 2005 Mark Smyk 2023 Peter Hollings 1987 Henry H. Halls 2006 Michael G. Mudrey 1988 Walter S. White 2007 Joseph Mancuso 1989 Jorma Kalliokoski 2008 Theodore J. Bornhorst 1990 Kenneth C. Card 2009 L. Gordon Medaris, Jr 1991 William Hinze 2010 William D. Addison & 1992 William F. Cannon Gregory R. Brumpton 1993 Donald W. Davis 2011 Dean M. Rossell 1994 Cedric Iverson 2012 James D. Miller 1995 Gene La Berge 2013 Tom Waggoner 1996 David L. Southwick 1997 Ronald P. Sage 2014 Laurel Woodruff 2015 Rodney J. Ikola 2023 GOLDICH MEDAL RECIPIENT Peter Hollings Goldich Medal Committee Serving through the meeting year shown in parentheses. Steve Kissin (2018-2023*) Lakehead University (Committee Chair) Dorothy Campbell (2019-2024*) Ontario Geological Survey Dean Peterson (2022-2025) Big Rock Exploration *Terms of the committee members were extended 2 years because of the cancelation of the 2020 meeting and the logistical difficulties of voting during the 2021 virtual meeting. xi �Proceedings of the 69th ILSG Annual Meeting – Part 1 Citation for the Goldich Medal Recipient to Peter Hollings ILSG Members, it is our privilege to present the citation for this year’s recipient of the prestigious Goldich Medal to Dr. Peter Hollings. Pete received his Bachelor of Science with Honours in Geology from the Royal Holloway and Bedford New College, University of London in 1992. He continued as a postgraduate research assistant at Royal Holloway and Bedford New College until 1994 when he enrolled as a Ph.D. student at the University of Saskatchewan. He earned his Ph.D. in 1998 and his doctoral dissertation was titled “Geochemistry of the Uchi subprovince.” He had a one-year postdoctoral fellowship at Saskatchewan, followed by a two-year NSERC postdoctoral fellowship at the University of Tasmania. Pete joined the faculty at Lakehead University in 2001 as an Assistant Professor and in 2009 was promoted to full Professor, a title he continues to hold. Since 2013 Pete has been Director of the Centre of Excellence for Sustainable Mining and Exploration (CESME) at Lakehead University. He has served as Chair of the Department of Geology and as interim Dean of the Faculty of Science and Environmental Studies at Lakehead. Pete has been recognized for his research through several awards. In 2004 he and his coauthors were awarded the Julian Boldy Award by the Mineral Deposits Division of the Geological Association of Canada for an outstanding paper. In 2008 he was awarded the William Harvey Gross Medal by the Mineral Deposits Division of the Geological Association of Canada for significant contributions to the field of economic geology by a geoscientist under the age of 40. He was part of the team recognized by an award in 2012 and in 2014 by AMIRA International. In 2015 he was named the NSERC Distinguished Researcher for Lakehead University and in 2016 he was named the Lakehead University Research Chair in the NSERC/CHIR category. He received the Howard Street Robinson Medal from the Geological Association of Canada in 2017. In 2021, a paper on which he was co-author was awarded the 2020 Cameron-Hall Copper Medal for the most outstanding scientific publication in the journal Geochemistry: Exploration, Environment, Analysis (GEEA). Pete was awarded the NOHFC Industrial Research Chair in Mineral Exploration for a term from 2020 to 2025. Pete has an impressive professional record of publications and presentations. As of 2022, he has been first author or co-author of 145 refereed journal articles, 13 book chapters, 234 reports, 136 papers in refereed conference proceedings, and 87 abstracts in conference xii �Proceedings of the 69th ILSG Annual Meeting – Part 1 proceedings. While this is an impressive list of accomplishments, it is Pete’s ongoing contributions to our understanding of Lake Superior geology and to the Institute on Lake Superior Geology that make him a worthy recipient of the Goldich Medal. Pete has extensively conducted research on the geology of the Lake Superior region and the broader Superior Province. He has focused on both the Midcontinent Rift System (MRS) and Archean greenstone belts and their mineral resources. More than 30 of his published papers in refereed journals are on Lake Superior geology as well as about half of both his 30 first-authored conference proceedings and 29 first-authored refereed abstracts. He has contributed to more than 60 technical reports on Lake Superior geology. Of his 27 invited presentations, half have dealt with Lake Superior geology. Pete has a significant number of publications and presentations relevant to the discovery and utilization of natural resources in the Lake Superior region. Some of his numerous economic geology publications and presentations on topics outside of the Lake Superior region are also applicable to our regional geology. An area of emphasis in Peter’s research is the application of geochemistry and petrology to explore for ore deposits, including NiCu-PGE deposits (e.g., Lac des Iles Mine and the Thunder Bay North igneous complex). His other areas of interest include igneous geochemistry of the MRS, Archean greenstone belts and granites, the tectonic setting of komatiites, and Archean gold deposits. As the Director of CESME, he provides leadership in promoting the discovery of and environmentally responsible exploration for natural resources. Pete has also made contributions to understanding of the natural history and environment of the Lake Superior region as demonstrated by numerous publications focused on the timing and evolution of local rocks and mineral deposits. Pete’s research is firmly rooted in field work and uses geochemical and other data to test existing ideas and concepts and to develop new ones. He has successfully used local and regional geochemical data to provide evidence and/or implications for broader geological questions, such as atmospheric oxygen in the Precambrian, continental growth and lithospheric recycling, the Superior Province cratonic keel, and the earliest phases of Midcontinent Rift development. In addition to data-driven new ideas and concepts, Pete’s research efforts have resulted in development of new analytical approaches that can be applied to the Lake Superior region and beyond. As a Professor at Lakehead University, Pete is actively involved the education of geoscientists through classroom teaching and thesis supervision. He is committed to training and mentoring as evidenced by the large role students play in his research. He has supervised and co-supervised 37 honours undergraduate research projects and 32 Masters graduate student theses. Most of this student-focused research has involved Lake Superior geology. His former students now have senior positions with government and industry, and some have gone on to complete PhDs. Moreover, he supports and encourages students to attend and present their research at ILSG. xiii �Proceedings of the 69th ILSG Annual Meeting – Part 1 ILSG plays a significant role in Pete’s professional activities. He has authored/co-authored (many with his students) 75 ILSG abstracts (nearly 4 per year), six ILSG field trip guidebooks, and ILSG Special Publication #1, Field trip guidebook for the Slate Islands, Ontario. At his very first ILSG meeting in 2002, Pete co-authored an abstract and served on the Student Paper Awards Committee. Pete has Chaired or Co-Chaired four in-person annual meetings (Nipigon, 2005; International Falls, 2010; Thunder Bay, 2012; Terrace Bay, 2019) and the virtual meeting in 2021. He has served as the Secretary of the ILSG from 2003 to the present. As Secretary, he is responsible for email communications with the members of ILSG. As a member of the Board, he attends and chairs the annual Board meeting. In ILSG Board meetings he always considers and defends the best interests of Institute. Pete is the ILSG webmaster and played a key role in the current design of the ILSG website which he updates and maintains. Through his efforts, Lakehead University is the digital archive to all of the past ILSG proceedings and field trip guidebooks and provides open access of this content worldwide. A testament to the quality and accessibility of these documents was ILSG’s receiving the 2016 Outstanding Geologic Field Trip Guidebook Series Award by the Geoscience Information Society (GSIS), which Pete accepted on behalf of the Institute. The stature of ILSG in the regional, national, and international geological communities has been elevated because of the increased presence of ILSG on the worldwide web, in large part because of Pete’s efforts. Over the years, we have all witnessed Pete in action. He is collegial, easy to approach and gets along well with others, whether they be students, colleagues, or industry geoscientists. He is both a good listener and a good speaker. And he is open-minded. He has high personal standards and expects them to be reflected in the work of his students and research colleagues. Pete is truly enthusiastic about the geology of the Lake Superior region and about ILSG. Pete has made and continues to make substantial contributions to the field of geology and to the Institute on Lake Superior Geology. Pete has more than met the qualifications that are engraved on the Goldich Medal itself: “For outstanding contributions to the geology of the Lake Superior region.” We congratulate the 2023 Goldich Medalist, Peter Hollings. Citation by: Theodore J. Bornhorst, Goldich Medalist 2008 Mark C. Smyk, Goldich Medalist 2005 xiv �Proceedings of the 69th ILSG Annual Meeting – Part 1 Honoring the Pioneers of Lake Superior Geology (Adopted by the Board of Directors, 2016) Preamble At the suggestion of Gene LaBerge, the 2016 executive board agreed to implement a program to recognize historic pioneers in the understanding of geology in the Lake Superior region. Beginning with the 2017 annual meeting, nominations will be accepted from the membership for geologists whose work was conducted primarily before inception of the institute in 1955. Biographical sketches of those pioneers will be presented at future annual meetings so that all might appreciate the value of their contributions. Selection of nominees will be decided in part by the organizing committee of each year's annual meeting, in consultation with the Board, to ensure equitable geographic representation in the selection process. Award Guidelines 1) Nominations from the membership will be submitted via the Institute web site and forwarded to the Chair of the next Annual Meeting. The nominations will be no more than half a page in length and will summarise the contribution of the nominee. 2) The Organising Committee will select one or two individuals to be highlighted at the next Annual meeting and submit those names to the Board for approval. 3) The nominator will be requested to prepare a brief presentation to be given during the next annual meeting with a summary to be included in the Proceedings volume. 4) Unsuccessful nominations will be kept by the Secretary for two years and forwarded to the next meeting Chair; these nominations may be resubmitted at a later date. The Board will review this award every five years. Pioneers of Lake Superior Geology 2017 Douglass Houghton (1809-1845) 2018-20 not presented 2021 Newton Horace Winchell (1839-1914) 2022 Thomas Leslie Tanton (1890-1971) 2023 Thomas Benton Brooks (1836-1900) xv �Proceedings of the 69th ILSG Annual Meeting – Part 1 2023 Nomination for Thomas Benton Brooks Pioneer of Lake Superior Geology “During many years Major (T.B.) Brooks was the chief authority in the region on matters pertaining to geology, the ores and the mines of the iron region of Lake Superior.”1 Shortly after the U.S. Civil War Major Thomas Benton Brooks moved to the Marquette Iron Range. There over the course of less than a decade, he became the premier geologist, prospector, mining and civil engineer, and mining company executive of the region. During these formative years of the iron ore industry, when the Lake Superior region was providing about one-quarter of the iron ore used in the U.S., he was employed by the Iron Cliffs Company, the predecessor of the ClevelandCliffs Company, the Michigan and Wisconsin Geological Surveys, and served as a consultant to iron ore exploration and mining companies of the region. His contributions had a significant role in mapping the Precambrian geology and iron ranges of Michigan and Wisconsin and a lasting impact on the iron ore industry of the region. As stated by Prof. C.R. Van Hise, Brooks’ successor as the premier geologist of the Lake Superior region2: “Notwithstanding the immense advantage which it has been to have Brooks’ work as a foundation, it has taken many years of labor fairly to complete the structural story to which Brooks contributed important chapters. Only those who have labored in the Lake Superior region and who understand its peculiar difficulties can give Brooks credit for the remarkable work he did. His geological work is my ideal of what should be done in a new region of complex geology.” Thomas B. Brooks was born on June 15, 1836 in Monroe, NY, near the New Jersey border, and died nearby on November 22, 1900. In 1852 at the age of 16, he joined a surveying crew of the Erie Railroad and rapidly advanced from woodsman to instrument man. In 1853 he was employed with the New York Topographic and Geological Survey and then entered the Engineering Department of Union College of Schenectady, NY in 1856, graduating in 1858 in civil engineering. He remained at Union College as an instructor for a year and then took part in topographical surveys in New York, New Jersey, Pennsylvania and the U.S. Gulf Coast. In 1 Quoted from an article by Chas. A. Lawton in the Daily Mining Journal, November 29, 1900 entitled The Late Major Thomas Benton Brooks: Biographical Sketch of a Man Whose Name is Intimately Associated With the Early Development of Michigan’s Iron Mines. The Mining Journal, the predominant daily newspaper of Marquette, Michigan and the Northern Peninsula of Michigan, was founded in 1841. 2 As quoted by Bailey Willis of the U.S. Geological Survey in an obituary for Major Brooks in the Proceedings of the American Association for the Advancement of Science, New Series, Volume 13, No. 325(March 22, 1901), 460-462. xvi �Proceedings of the 69th ILSG Annual Meeting – Part 1 1860 he attended a series of lectures on geology given by Prof. J.P. Lesley former state geologist of Pennsylvania and Professor of Geology at the University of Pennsylvania. This was his only formal education in geology. He volunteered for the Union Army in 1861 and organized an engineering company that had a distinguished record during numerous Civil War campaigns. He retired from the Union Army in 1864 as a brevet colonel after being wounded in the battle of Denly’s Bluff, but referred to himself after the war as Major Brooks. In 1865 after leaving the Union Army he accepted a position with the Geological Survey of New Jersey where he conducted magnetic surveys with a dip needle to locate iron ores and was put in charge of mines and furnaces. Shortly thereafter, he was induced to take charge of the mines of the Iron Cliffs Company in the Marquette Iron Range as vice-president and general manager. He moved to Negaunee, Michigan, where his practical knowledge of geology and engineering, leadership skills, originality, keen powers of observation and deduction, and intense work ethic served him, the company, and the Lake Superior region well. This is where his extensive geological studies began and where he developed the instruments and methodology to exploit the iron ores of the Lake Superior region. He brought the dip needle to the Lake Superior region and was among or possibly was the very first, to use it in iron ore exploration and geologic mapping in the region. He also pioneered the dial (Sun) compass, which he modified for geologic use from the surveying solar compass developed by W.A. Burt. In 1869 he resigned from the Iron Cliffs Company and was given the responsibility of mapping and reporting on the Marquette Iron Range and was placed in charge of the Economic State Geological Survey of the district by the Michigan Geological Survey, essentially becoming the State Geologist of the Northern Peninsula. He received no salary for this position, but he was allowed to receive private funds from numerous iron ore companies and mines. Unfortunately, his intense work schedule took a toll on his health that caused him to leave Marquette with his family in the winter of 1872-73 for London, England and eventually Dresden, Germany, where he hoped to regain his health, but failed to do so. During this period he prepared reports on his iron range geologic studies for publication by the Michigan and Wisconsin Geological Surveys (Brooks, 1873 and 1880), articles on the geology of the region and magnetic surveying instruments and their use published in various journals including the American Journal of Science and Arts (Brooks and Pumpelly, 1872; Brooks, 1875), and co-authored the book “Iron Ores of Missouri and Michigan” (Pumpelly, Brooks, and Schmidt, 1876). During his years involved with the geology and ores of the Lake Superior region Major Brooks made numerous advances in the geological knowledge of the region that have served as a foundation for future studies and developed methods and instruments that proved useful for exploiting the ores of the region for many years. The following are a list of his major lasting accomplishments: • • He with the assistance of R. Pumpelly and R.D. Irving developed the dial (Sun) compass for geologic studies based on the principal of Burt’s surveying solar compass which together with the dip needle that he brought from the Geological Survey of New Jersey were used in the Lake Superior region for nearly a century to locate and outline iron-rich rocks and ores. His publications on these instruments led to their extensive worldwide use. He established procedures for conducting magnetic surveys for geological purposes in the Lake Superior region and methods of interpreting the observations of the surveys based on empirical studies. xvii �Proceedings of the 69th ILSG Annual Meeting – Part 1 • • • • • • • He was the first to describe the magnetic characteristics of the minerals and rocks of the Lake Superior region. He (Brooks, 1872a) recognized that magnetic anomalies observed in the area of non-magnetic Paleozoic (then Silurian) sedimentary rocks of the eastern part of the Northern Peninsula of Michigan were likely derived from the basement Precambrian rocks that crop out to the west. Accordingly, these anomalies could be used to trace the basement rocks and their structure beneath the sedimentary rocks. Furthermore, he realized that anomaly characteristics could be used to determine the depth to magnetic sources and thus, the thickness of the sedimentary rocks. In a similar manner he understood that perhaps the depth of Lake Superior could be determined from analysis of the lake magnetic anomalies. He founded the first assay facility for iron ores in the Lake Superior region in the city of Marquette which facilitated iron ore mining in the region. He conducted one of the first geological surveys of the Marquette, Menominee, Crystal Falls, and Gogebic Iron Ranges. He was the first to understand that the Marquette Iron Range occurs within a 75-km long syncline extending to the west from near Marquette, Michigan (Allen and Martin, 1922). He recognized the stratigraphic position of the copper-bearing rocks of the Northern Peninsula of Michigan and suggested the name Keweenawian (note his spelling) for the age of these rocks in American Journal of Science and Arts articles of 1872 and 1875. Subsequently, the term Keweenawan has been used for these rocks. He had an important role in developing safe, efficient methods of mining iron ores of the Lake Superior region (Brooks, 1972b). He was intensely interested in the education of his children and supported the studies of his son, Alfred Hulse Brooks, a famed geologist of the U.S. Geological Survey, Alaska Branch, who is honored by naming of the Brooks Range of Alaska after him. These are all significant contributions that have had a profound role in understanding of the geology of the Lake Superior region and the exploitation of its ores. They have largely gone unrecognized for the past century and a half, but they clearly distinguish Major Thomas Benton Brooks as a Pioneer of Lake Superior geology. References Allen, R.C., and Martin, H.M., 1922. A brief history of the Geological and Botanical Survey of Michigan. Michigan History Magazine, Volume VI, No. 44: 675-750. Lawton, C.A., 1900. The Late Major Thomas Benton Brooks: Biographical Sketch of a Man Whose Name is Intimately Associated with the Early Development of Michigan’s Iron Mines. The Daily Mining Journal, November 29, 1900. Pumpelly, Raphael, Brooks, T.B., and Schmidt, A., 1876. Iron Ores of Missouri and Michigan. G.P. Putnam’s Sons, New York: 624. Willis, B., 1901. Thomas Benton Brooks. Proceedings of the American Association for the Advancement of Science, Science, New Series, Volume 13, No. 325: 460-462. William J. Hinze, Purdue University xviii �Proceedings of the 69th ILSG Annual Meeting – Part 1 APPENDIX: PUBLICATIONS OF T.B. BROOKS Brooks, T.B., 1872a. On the use of the magnetic needle in mineral explorations on Lake Superior. Van Nostrand’s Eclectic Engineering Magazine (1869-1879), August 1, 1872; Volume 7, No. 44, American Periodicals: 161. Brooks, T.B., 1872b. An analysis of the cost and description of the methods of mining employed in the Marquette Iron Region, Lake Superior, Michigan. Transactions of the American Society of Civil Engineers, Volume XXXIV: 18. Brooks, T.B., and Pumpelly, R., 1872. On the age of the copper-bearing rocks of Lake Superior. American Journal of Science and Arts, Third Series, Volume III, No. XVIII: 428-432. Brooks, T.B., 1873. Geology of Marquette Iron Range, Geology of the Menominee Iron Range, and Geology of the Gogebic and Montreal Iron Ranges. Michigan Geological Survey, Volume 1, Chapters IV, V, VI, VII, and VIII, Part 1, Iron-Bearing Rocks: 117-243. Brooks, T.B., 1875. On the youngest Huronian rocks south of Lake Superior and the age of the copperbearing series. American Journal of Science and Arts, Third Series, Volume III, No. XI: 206211. Brooks, T.B., 1880. Geology of the Menominee Region. In Chamberlin, T.C. (ed.), Geology of Wisconsin, Volume 3, Part 7, Chapters 1, 2, and 3: 430-552. xix �Proceedings of the 69th ILSG Annual Meeting – Part 1 In Memoriam Stephen Allard Stephen Thomas Allard, 59, of Winona, MN, passed away on Friday, September 16, 2022. He was born May 2, 1963, in Manchester, New Hampshire and graduated from Manchester Central High School before going on to receive both his bachelor’s and master’s degrees from the University of New Hampshire, and his doctorate from the University of Wyoming. In 2002, Stephen moved to Winona, MN to begin his career as a professor at Winona State University. After serving for 19 years as a faculty member in the Department of Geoscience, Stephen retired from the university in December of 2021. During his tenure at WSU, Stephen served on several committees and taught 13 different courses drawing on his expertise in hard rock and structural geology. Stephen was dedicated to teaching and mentoring students through field-based research, leading courses and field trips throughout the United States, notably the many summers spent in the Black Hills of South Dakota. (modified from Hartford Courant newspaper) xx �Proceedings of the 69th ILSG Annual Meeting – Part 1 In Memoriam Steven A. Hauck This Fall the Institute on Lake Superior Geology lost a dedicated geologist and friend, Steve Hauck, who was a regular attendee of ILSG (since at least 1984) and worked on countless projects in the Lake Superior Region while employed at the Natural Resources Research Institute (NRRI) in Duluth, MN. During that time, Steve was a mentor to numerous geologists in the region throughout their early and continuing careers. Steve Hauck had just recently moved from Duluth to Euclid, OH where he passed away on October 6, 2022 at the age of 73. Steve as born on May 16, 1949, in Rochester, NY, where he graduated from Gates-Chili High School prior to attending Albion College where he earned a BS in geology. He enlisted in the US Army where he was trained as a Chinese translator and married fellow Albion student and the love of his life Barbara Horsley to whom he was married for 50 years. Steve loved to talk about geology on car trips and impressed his future father-in-law with his knowledge and enthusiasm. Steve later earned a MS degree in geology from the University of North Carolina before embarking on a geology career that eventually led him around the globe. He was first employed by Union Carbide in Grand Junction, CO, where he was responsible for exploration for uranium in the 4-corners region. While at Union Carbide he was also responsible for developing a world-wide exploration program in search of IOCG deposits (as they were later called) and visited many similar deposits including Olympic Dam, Pilot Knob and Pea Ridge in Missouri, and Kiruna iron deposits in Sweden to name a few. Steve’s first ILSG talk (1984) pertained to the distinguishing characteristics of these types of deposits and was titled “Comparison of Middle Proterozoic Iron Oxide Rich Ore Deposits, Mid-Continent, USA, South Australia, Sweden, and the Peoples Republic of China.” Steve was then hired as the second employee of the Minerals Division of the NRRI in 1984 as Research Director and Manager where he worked for over 30 years. He was initially responsible for building and equipping the division, focusing on economic geology, and initially hired graduate students from the University of Minnesota Duluth (UMD). During his tenure at the NRRI, Steve hired well over 30 UMD students (both undergraduate and graduate students) as well as many geologists in their early career years. Projects that he and his coworkers researched ranged from clay deposits in SW MN, to Cu-Ni and Fe-Ti deposits in the Duluth Complex, to the Biwabik Iron Formation, to geochemistry on a wide range of rocks spanning from the Archean to the Cretaceous. He worked closely with fellow geologists at the Minnesota Geological Survey, Minnesota Department of Natural Resources Lands and Minerals, and the U.S. Geological Survey, and collaborated with many geologists across the U.S. and overseas in academia and industry. xxi �Proceedings of the 69th ILSG Annual Meeting – Part 1 Steve was a Co-chair of the ILSG meeting for its 50th Anniversary in Duluth in 2004 and served on the Board of Directors for three years. Overall, Steve participated in three ILSG talks (one as primary author) and ten posters (four as primary author). Steve loved to talk about rocks and encouraged his co-workers to give talks and poster presentations at many of the ILSG meetings. Steve was an avid birder, cultivator of native plants, and shutterbug. He was predeceased by his youngest son, Davis, and his parents Arthur and Jean (Doron). He is survived by wife Barbara, son Steven (Danette), sisters Carlin Eagan (Daniel), Sandra Doron, and Mary McGuire (Mark), and two grandchildren Levi and Abigail. (modifed from Duluth Tribune newspaper) xxii �Proceedings of the 69th ILSG Annual Meeting – Part 1 In Memoriam Manfred Kehlenbeck Manfred was born in Bremen, Germany in 1937 to parents Emma and Theodor. This is where he spent his childhood, amidst the horrors of World War II, like so many of Europe's children. At age 14, Manfred immigrated with his parents to the U.S., landing in New York in July of 1952 and settling with relatives in Long Island until they could become established. Here he completed his high school education, then attended Hofstra University for his undergraduate degree. It was there that he was introduced to the science of geology, which became his lifelong interest and focus of his future education and career. It was also on Long Island that he met Elenore, who would eventually become his wife of 53 years. Manfred went on to Syracuse University in upstate New York to attain his M.Sc. in Geology and gain field experience in the beautiful Adirondack Mountains. And then, moving even further north, he attended Queen's University in Kingston, Ontario where he achieved his Ph.D. Since he has always planned to teach, he then accepted a position at the young Lakehead University in Thunder Bay, Ontario. Here he soon became fascinated with the Precambrian geology of the area and greatly enjoyed his teaching duties. He was a born teacher, winning Teacher of the Year awards both at Lakehead and in the Province. He served five terms as a Geology Department Chair, guiding the department into its M.Sc. program. His years at Lakehead were productive and happy ones. Upon his retirement, Manfred was able to expand on other interests and travel widely. In addition to trips in Canada, the U.S. and Germany, there were four “special” ones – professionally to Russia and China, and then the most fascinating ones, to the Arctic and Antarctic. His other areas of interest and hobbies were in watercolour and pen and ink drawings of local scenes, especially forests, lakes, rocks, and old buildings of NW Ontario xxiii �Proceedings of the 69th ILSG Annual Meeting – Part 1 and many views of Old Fort William. Many of his works hang in Thunder Bay homes. He became an avid gardener, curler and opera lover, and spent many hours volunteering for various causes. It was a happy and fulfilling retirement for Manfred and Elenore until his last illness and unexpected passing in the early morning hours of July 7, 2022 when he drew his last breath at the Thunder Bay Regional Health Sciences Centre after emergency surgery. Our thanks to the I.C.U. staff and especially to Katie and Michaela who were so kind and thoughtful during those last terrible hours, and to N.P. Crystal Kaukinen for the many years of care she had provided. Thanks also to all who have been so kind with phone calls, cards, offers to help, food and rides. Special thanks to Barb Morriss for always checking in, to Sam and Georgina Spivak for all the rides, and to Vince and Frieda DeSa who have been here for me everyday with their help and support – without them, I don't know how I would have survived this devastating time. Manfred was a good, kind, generous man, and loving and devoted husband. He is sorely missed. Auf Wiedersehen mein lieber Manfred. Published by The Thunder Bay Chronicle Journal on Aug. 13, 2022. xxiv �Proceedings of the 69th ILSG Annual Meeting – Part 1 Eisenbrey Student Travel Awards The 1986 Board of Directors established the ILSG Student Travel Awards to support student participation at the annual meeting of the Institute. The name “Eisenbrey” was added to the award in 1998 to honor Edward H. Eisenbrey (1926-1985) and utilize substantial contributions made to the 1996 Institute meeting in his name. “Ned” Eisenbrey is credited with discovery of significant volcanogenic massive sulfide deposits in Wisconsin, but his scope was much broader—he has been described as having unique talents as an ore finder, geologist, and teacher. These awards are intended to help defray some of the direct travel costs of attending Institute meetings, and include a waiver of registration fees, but exclude expenses for meals, lodging, and field trip registration. The number of awards and value are determined by the annual Chair in consultation with the Secretary and Treasurer. Recipients will be announced at the annual banquet. The following general criteria will be considered by the annual Chair, who is responsible for the selection: 1) The applicants must have active resident (undergraduate or graduate) student status at the time of the annual meeting of the Institute, certified by the department head. 2) Students who are the senior author on either an oral or poster paper will be given favored consideration. 3) It is desirable for two or more students to jointly request travel assistance. 4) In general, priority will be given to those in the Institute region who are farthest away from the meeting location. 5) Each travel award request shall be made in writing to the annual Chair, and should explain need, student and author status, and other significant details. Successful applicants will receive their awards during the meeting. xxv �Proceedings of the 69th ILSG Annual Meeting – Part 1 Joe Mancuso Student Research Awards The 2005 Board of Directors established the ILSG Student Research Fund with $10,000 US from the Institute’s general fund to encourage student research on the geology of the Lake Superior region. A minimum of two awards of $500 US each for research expenses (but not travel expenses) will be made each year. Students are expected to present their research orally or during a poster session at an ILSG meeting. The award winners will also be automatically eligible for the Eisenbrey Travel Awards. To allow the fund to grow, the Fund will receive one-half of any additional proceeds from each annual meeting, after all other commitments and expenses are covered. • The ILSG Board of Directors will be responsible for selecting a minimum of two awards each year. The ILSG Treasurer will issue the awards. • The ILSG Student Research Fund is available for undergraduate or graduate students working on geology in the Lake Superior region. • The applications are due to the ILSG Secretary by August 31st of each year. Awards will be made by October 1st of each year. • Names of the award recipients will be announced at the next annual meeting and posted on the ILSG website. • Details of the application process can be found on the ILSG web site. • The proposal will need to be signed by the researcher’s supervisor. The 2012 Board of Directors approved modification of the fund’s name, adding “Mancuso” to reflect the many contributions of Joseph Mancuso to the organization and sizeable donations made in his name. “Doc Joe,” as he was known by his students, taught geology for 36 years at Bowling Green State University, Ohio. He advised many graduate students in field-oriented research, and frequently brought them to Institute meetings. Joe was the 2007 Goldich Medalist. In fall 2022, the ILSG Board of Directors selected two students to be granted research funding of $1000.00 each from the Joe Mancuso Student Research Fund. The awardees were: Itai Bojdak-Yates Lawrence University Department of Geosciences TOPIC: Detrital zircon provenance study of Paleozoic sandstones from Wisconsin Lillian Glodowski University of Wisconsin- Eau Claire TOPIC: Petrogenesis of the Lynne Zn-CuPb Deposit, Oneida Co., Wisconsin Evan Weber University of Wisconsin- Eau Claire TOPIC: U/Pb Geochronology and Zircon Trace Element Geochemistry of the Pembine-Wausau Terrane of the Proterozoic Penokean Orogen, Wisconsin xxvi �Proceedings of the 69th ILSG Annual Meeting – Part 1 Doug Duskin Student Paper Awards Each year, the Institute selects the best of student presentations and honors the presenters with a monetary award. Funding for the award is generated from registrations of the annual meeting, and from generous donations to the fund in honor of Doug Duskin—an exploration geologist and longtime friend of the Institute. The 2012 ILSG Board of Directors approved adding Doug’s name to the award to acknowledge his contributions, and distribute those donations in a manner that would have pleased him. The Duskin Student Paper Committee is appointed by the Meeting Chair. Criteria for best student paper—last modified by the Board in 2001—follow: 1) The contribution must be demonstrably the work of the student. 2) The student must present the contribution in-person. 3) The Student Paper Committee shall decide how many awards to grant, and whether or not to give separate awards for poster vs. oral presentations. 4) In cases of multiple student authors, the award will be made to the senior author, or the award will be shared equally by all authors of the contribution. 5) The total amount of the awards is left to the discretion of the meeting Chair in conjunction with the Secretary, but typically is in the amount of about $500 US (increase approved by Board, 10/01). 6) The Secretary maintains, and will supply to the Committee, a form for the numerical ranking of presentations. This form was created and modified by Student Paper Committees over several years in an effort to reduce the difficulties that may arise from selection by raters of diverse background. The use of the form is not required, but is left to the discretion of the Committee. 7) The names of award recipients shall be included as part of the annual Chair’s report that appears in the next volume of the Institute. Student papers will be noted on the Program. xxvii �Proceedings of the 69th ILSG Annual Meeting – Part 1 Board of Directors Board appointment continues through the close of the meeting year shown in parentheses, or until a successor is selected. The terms of Board members were extended 2 years because of cancellation of the 2020 meeting, and the difficulties of virtual voting by the membership during the 2021 meeting. Mike Easton, Chair (2022-2025) — Ontario Geological Survey Mark Smyk (2019-2024*) — Lakehead University Esther Stewart (2018-2023*) – Wisconsin Geological & Natural History Survey Peter Hollings — Secretary (2019-2024*) — Lakehead University Mark A. Jirsa — Treasurer (2022-2025) — Minnesota Geological Survey xxviii �Proceedings of the 69th ILSG Annual Meeting – Part 1 Field Trip Leaders and Guidebook Authors Field trips have been the mainstay of the ILSG since its inception 69 years ago. We want to give a special thanks to the field trip leaders and guidebook authors who volunteered their time and talent in carrying that tradition forward. 1) Precambrian geology of the Chippewa River Valley Rob Lodge- UW- Eau Claire Bob Hopper- UW- Eau Claire 2) Wisconsin’s Paleozoic stratigraphy and tour of Crystal Cave Carsyn Ames- Wisconsin Geological and Natural History Survey Esther Stewart- Wisconsin Geological and Natural History Survey William Batten- Wisconsin Geological and Natural History Survey Eric Stewart- Wisconsin Geological and Natural History Survey Ian Orland- Wisconsin Geological and Natural History Survey 3) Precambrian geology of the Eau Claire River Valley Rob Lodge- UW- Eau Claire Evan Weber- UW- Eau Claire (student) 4) Quaternary geology and geomorphology of the Eau Claire Region Doug Faulkner- UW- Eau Claire Elmo Rawling- Wisconsin Geological and Natural History Survey xxix �Proceedings of the 69th ILSG Annual Meeting – Part 1 REPORT OF THE 68th ANNUAL MEETING OF THE INSTITUTE ON LAKE SUPERIOR GEOLOGY The Ontario Geological Survey (OGS), with support from the Geological Survey of Canada (GSC), hosted the 68th Annual Institute on Lake Superior Geology on May 07 – 12, 2023 in the “Cavern” at Science North in Sudbury, Ontario. The meeting consisted of two days of technical sessions with pre- and post-technical session field trips. First, we would like to thank the meeting sponsors for their generous support, either through direct funding or in-kind support, namely: the Centre for Excellence and Sustainable Mineral Exploration in Thunder Bay, Gel Exploration Limited, the Northwestern Ontario Prospectors Association, Vale Canada, and the Ontario Geological Survey. We also thank the Individual Contributors to the Student Travel Scholarship fund: Mary Kay Arthur, Mike Beauregard, Ben Berger, Terry Boerboom, Jim DeGraff, Michael and Monica Easton, Dick Heglund, Joanna Hodge, Bob Mahin, Jim Miller, Dean Peterson, Mark and Laurie Severson, Al MacTavish and Graham Wilson. The 2022 meeting was the first in-person meeting held since the 2019 Terrace Bay meeting. An ILSG meeting questionnaire, which ran from January 20 to February 20, 2022, was key to shaping the format and venue of the meeting during a period of rapidly changing COVIDrelated regulations, with most responses favouring an in-person meeting. For technical reasons, a hybrid meeting was not possible. Total meeting registration was 80, including 12 students. This registration is about 80% of the attendance of the last two Sudbury area meetings (Sudbury 1997; Sault Ste. Marie 2006), and was a great turnout given the COVID-related travel restrictions still in place at the time of the meeting. Attendance from the United States was excellent, with attendance from the Sudbury area lower than expected, for unknown reasons. Despite the somewhat lower attendance, the technical program was nevertheless excellent, with a strong focus on Midcontinent Rift geology and mineralization in the Lake Superior region. In addition, four presentations focused specifically on Sudbury area geology. There was also time in the schedule for several impromptu presentations on a variety of topics on Wednesday afternoon prior to the announcement of the student awards. Proceedings Volume 68 was published in two parts. Part 1 – Program and Abstracts, compiled and edited by Michael Easton (OGS), contains 28 published abstracts for 21 oral and 8 poster presentations (one poster did not have an abstract). Students presented 5 oral and 5 poster presentations. Part 2 – Field Trip Guidebooks, also was compiled and edited by Michael Easton. It contains descriptions of three pre-meeting and two post-meeting field trips. Hard copies of the Abstract Volume and Field Trip Guidebooks for trip participants were printed by Johanne Roux and Carlo Castrechino (OGS) after it proved impossible to find a commercial printer who could produce the volumes in time for the meeting. Both volumes are available for download from the Institute on Lake Superior Geology website. Monica Easton is thanked for assisting in preparing the digital versions of both volumes. The 68th ILSG marked only the second time in the Institute’s long history that its annual meeting was held in Sudbury, the last time being in 1997. Since the discovery of distal ejecta xxx �Proceedings of the 69th ILSG Annual Meeting – Part 1 from the Sudbury impact in the western Lake Superior area in 2005, many members of the Institute had suggested that the time was right for another Sudbury meeting. The meeting location enabled organizers to offer five field trips that showcased a variety of Proterozoic rocks in the Sudbury area itself, as well as along the north shore of Lake Huron. Three field trips focussed on the geology and mineralization related to the Sudbury Structure, and the organizers wish to thank the local exploration companies that graciously provided information and access to their properties. Parts of the other two of the field trips had been offered at previous ILSG annual meetings (e.g., Sudbury 1997; Sault Ste. Marie 2006), but both greatly benefitted from the new mapping, research, discoveries and interpretations that had taken place in the intervening years. COVID-related shortages of rental vehicles and/or drivers led to pre-meeting trips being held over several days, which unexpectedly, provided more opportunities for attendees to take in several field trips if they wanted. All the field trips, and the meeting itself, were blessed with sunny weather and a minimum number of pesky insects. Total field trip participation was 96 (excluding leaders and volunteer drivers). A list of field trips is provided below (numbers correspond to trip numbers in the Guidebook volume): Pre-meeting field trips (and leaders) on Saturday, May 07; Sunday, May 8, and Monday, May 9. 5) A cross-section through the Huronian Supergroup at Elliot Lake, Ontario (Michael Easton, Ontario Geological Survey) (May 7) 2) Geology of the Grenville Front in the Sudbury area (Michael Easton, Ontario Geological Survey) (May 8) 1) Traverse across the Sudbury Impact Structure (Wouter Bleeker, Geological Survey of Canada, and Sandra Kamo, University of Toronto; Michael Lesher and Henning Seibel, Laurentian University) (Two-day trip, May 8 and May 9) Post-meeting field trips (and leaders) on Thursday, May12 3) Magmatism and brecciation in the Footwall Rocks of the southwestern Sudbury Structure (Caroline Gordon, Ontario Geological Survey; Carol-Anne Généreux, Laurentian University and Terrane Geoscience; and Brad Clarke, SPC Nickel Corporation) 4) An overview of the geology of the Sudbury Structure (Shirley Péloquin, Ontario Geological Survey) Many registrants attended the welcoming reception on Monday evening, which included an IMAX theatre presentation on “Dinosaurs of Antarctica”. Furthermore, the vast majority of registrants and invited guests attended the annual ILSG banquet on Tuesday night. Although a Homer Award overview presentation was given, no “recipients” were identified during the 2022 annual meeting, or in the previous 3 years! As always, a highlight of the post-banquet activities was presentation of the 2022 Goldich Medal. This year’s very deserving recipient was Terry Boerboom. The Goldich Medal citation was presented by Mark Jirsa, his colleague for many years. Mark described Terry’s contributions to the ILSG and to the greater understanding of Minnesota’s geology over several decades during his time as a student and his 35 years with the Minnesota Geological Survey. Terry is indeed a worthy recipient of this prestigious award. The 68th ILSG saw a return to the usual post-banquet guest speaker tradition. Andy Parmenter xxxi �Proceedings of the 69th ILSG Annual Meeting – Part 1 of the Canadian Nuclear Waste Management Organization (NWMO) travelled from Toronto to give an overview of NWMOs Geoscience site characterization of the Revell batholith in the Ignace area of northwestern Ontario. His talk provided detailed insights into the 3-D character of a Neoarchean granodioritic to granitic intrusion, based on detailed mapping and geophysical, seismic, and geochemical studies, as well as from multiple 1 km-long research cores obtained from the batholith. In 2022, the student paper committee had its usual difficult job of selecting the best among five excellent oral presentations and five poster presentations for the Doug Duskin Student Paper Awards. The committee awarded four prizes, with the best talk award going to Rebecca Price for her talk on “Mineralogy and Petrology of the Good Hope Carbonatite Complex, Marathon, ON” and the best poster award going to Khalid Yahia for his poster on “Geochemical and isotopic composition of Midcontinent Rift-related intrusions of the Thunder Bay North Igneous Complex, northwestern Ontario, Canada”. Runner-up prizes went to Audray Hinkenmeyer for her talk on “Characterizing Late Wisconsinan Rainy Lobe till from the Hudson Bay Lowlands to SW Minnesota: Insights on provenance and ice sheet behavior during Late Wisconsin glaciation” and to Katherine Langfield for her poster on “Slip Kinematics of the Hancock Fault in the Midcontinent Rift System, Keweenaw Peninsula, Michigan”. Eisenbrey Student Travel Grants were given to three students: Connor Caglitoti (Lakehead University), Katherine Langfield (Michigan Technical University), and Miles Harbury (University of Wisconsin, Milwaukee). The Institute’s Board of Directors met on Tuesday, May 10, 2022, and a brief overview of the meeting notes is provided below: 1. Accepted report of the Chairs for the 67th ILSG, Virtual Meeting; as published on the ILSG web site, and minutes of last Board meeting in May 2021. 2. Received, discussed, and accepted 2021-2022 ILSG Financial Summary. 3. Received, discussed, and accepted 2021-2022 report of the Secretary (Hollings). 4. Approved Michael Easton as on-going ILSG Board member 5. Discussed and approved renewal of Mark Jirsa as Institute Treasurer (end of term 2022). This was later approved by a vote of the membership. 6. Discussed and approved replacing Dan England as the “member from industry” on the Goldich Committee (end of term 2022) with Dean Peterson. 7. Approved Eau Claire as the site for the 69th annual ILSG meeting. The meeting will be hosted by Robert Lodge and Esther Stewart. 8. Reviewed and approved the guidelines for the Honouring the Pioneers of Lake Superior Geology with the charge that the document will be reviewed as needed. 9. Future meeting locations were discussed. Ted Bornhorst offered Houghton in 2024, Peter Hinz has offered Kenora as a future site and Mark Jirsa is keen to host the Mountain Iron meeting that was cancelled in 2020 because of the pandemic. In a subsequent discussion, Bernie Saini-Eidukat expressed a willingness to organize a meeting in St. Cloud. 10. The cost of insurance was discussed and it was agreed that the Board of Directors insurance and field trip insurance should be maintained for future meetings and that the costs would be included in the cost of each meeting. The fact that the Institute meets in both the US and Canada is an added complication. xxxii �Proceedings of the 69th ILSG Annual Meeting – Part 1 11. Jirsa advised the board of the donation of polar bear carvings from Mike Beauregard, and it was agreed that a silent auction would be held during the meeting with funds going to support student travel. Dan England later donated two samples with visible gold and, combined, these items raised $395 for the Eisenbrey fund 12. Bornhorst advised that there are a small number of hard copies missing from the MTU archives and that he will work to fill these. It was agreed that the ILSG would make a donation of $1 per member (minimum $100) each year to the library as a “thank you” for their efforts 13. The 68th ILSG meeting was a great success and we wish to thank all the people who contributed to that success, including staff of the Ontario Geological Survey who were pressed into action as editors, field trip leaders and drivers. Patty Cobin and Ted Bornhorst (A.E. Seaman Mineral Museum, Michigan Technological University) handled the premeeting registration. Ted also supplied the poster boards. Thanks go also to the staff at Science North who helped the meeting run smoothly as well as Bryston’s on the Park in Copper Cliff who provided a first-class banquet dinner, as well as lunches and snacks during the technical sessions. Michael Easton (OGS) and Wouter Bleeker (GSC) Co-Chairs, 68th Institute on Lake Superior Geology xxxiii �Proceedings of the 69th ILSG Annual Meeting – Part 1 TECHNICAL PROGRAM xxxiv �Proceedings of the 69th ILSG Annual Meeting – Part 1 TECHNICAL PROGRAM SUNDAY APRIL 23, 2023 All field trips begin and end at The Lismore Hotel 8:00 am - 5:00 pm PRE-MEETING FIELD TRIPS 1) Precambrian geology of the Chippewa River Valley Rob Lodge and Bob Hooper – UW- Eau Claire 2) Wisconsin’s Paleozoic stratigraphy and tour of Crystal Cave Carsyn Ames – Wisconsin Geological and Natural History Survey 4:00 pm - 10:00 pm Registration (Wilson Hall Lobby) 7:00 pm - 10:00 pm Welcoming Reception (Wilson Hall A/F) MONDAY APRIL 24, 2023 7:30 am – 11:30 am Registration (Wilson Hall Lobby) 8:00 OPENING REMARKS (Wilson B) Rob Lodge and Carsyn Ames, Co-Chairs, 2023 ILSG TECHNICAL SESSION I Session Chair: James DeGraff- Michigan Technological University * denotes a student eligible for Best Student Paper Award. To be eligible students must have graduated no more than one month before the ILSG meeting, be first author, and present the paper at the meeting. + denotes author that will present abstract, if different than the first author. 8:10 William J. Hinze, and +William Cannon 2023 Pioneer of Lake Superior Geology: Thomas Benton Brooks 8:30 Erika Vye and William Rose Geoheritage as an educational tool to explore relationships with land and water in the Keweenaw 8:50 William Rose New work developing Keweenaw geoheritage awareness 9:10 Matt Carter and Donald Elsenheimer Workshop Outcomes and Updates for the Minnesota Department of Natural Resource’s Drill Core Library 9:30 Dean Peterson On the Importance of Geologic Maps for Mineral Exploration 9:50 9:50 END OF TECHNICAL SESSION I COFFEE BREAK xxxv �Proceedings of the 69th ILSG Annual Meeting – Part 1 TECHNICAL SESSION II Session Chair: Ben Drenth- USGS and Amy Radakovich Block- Minnesota Geological Survey 10:00 Dana Peterson, Paul Bedrosian, and Carol Finn Subsurface characterization of the Duluth Complex and related intrusions from 3D modeling of gravity and magnetotelluric data 10:20 Paul Bedrosian, Tien Grauch, Laurel Woodruff, William Cannon, Benjamin Drenth, Esther Stewart, Dana Peterson, and James Jones Interpreted geophysical cross-sections through the Lake Superior region: Investigating three billion years of geologic history in sixteen lines of data 10:40 Tien Grauch, Sam Heller, Esther Stewart, and Laurel Woodruff Exploring the geology of the Midcontinent Rift under western Lake Superior using a preliminary velocity model of seismic line GLIMPCE C 11:00 Jennifer Smith, Victoria Tschirhart, Loughlin Tuck, Randy Enkin, and David Roy-Guay Exploring the application of full tensor magnetic gradiometry to better define conduit type NiCu-PGE targets 11:20 END OF TECHNICAL SESSION II 11:20-1:00 LUNCH BREAK and LSG BOARD OF DIRECTORS MEETING - lunches not provided to conference attendees- 11:20-1:00 Student Career Panel- (L.E. Phillips Memorial Public Library- 400 Eau Claire St. in the Riverview Room (Room 306)) TECHNICAL SESSION III Session Chair: Marcia Bjørnerud- Lawrence University 1:10 Wouter Bleeker, Jennifer Smith, Michael Hamilton, Sandra Kamo, Pete Hollings, Michael Easton, and Robert Cundari The Midcontinent Rift System: Neither triple junction nor failed rift? 1:30 Matthew Brzozowski, +Pete Hollings, Jing-jing Zhu, and Robert Creaser Contributions of diverse mantle sources during the early stages of Midcontinent Rift formation — Implications for a passive rifting model 1:50 *Daniel 2:10 *Katherine Langfield, 2:30 END OF TECHNICAL SESSION III Lizzadro-McPherson, James DeGraff and Ian Gannon Structural analysis and slip kinematics of the Keweenaw fault system between Bête Grise Bay and Gratiot Lake, Keweenaw County, Michigan James DeGraff, and Nolan Gamet Slip Kinematics of the Keweenaw and Hancock Faults within the Midcontinent Rift System, Upper Peninsula of Michigan xxxvi �Proceedings of the 69th ILSG Annual Meeting – Part 1 2:30 COFFEE BREAK TECHNICAL SESSION IV Session Chair: Pete Hollings- Lakehead University and 2023 Goldich Medalist 2:50 *Tianna 3:10 *Sam Ghantous, 3:30 *Blaize Briggs and Mary Louise Hill Quetico-Wabigoon Subprovince Boundary in the Superior Province north of Thunder Bay, Ontario, Canada 3:50 Margaret Upton, Phillip Larson, Allan MacTavish, and Peter Hinz Summary of the 2022 ILSG Field Trip to Iceland 4:10 END OF TECHNICAL SESSION IV 4:10 POSTER VIEWING - AUTHORS WILL BE PRESENT AT THEIR POSTERS 6:00 RECEPTION AND CASH BAR (Wilson Hall A/F) 7:00 Groeneveld, Peter Hollings, Wyatt Bain, and Lionnel Djon Petrography, geochemistry, and mineralization of the Archean Titan (Roaring River) intrusion, Northwestern Ontario Noah Phillips, Alex Lusk, Julie Newman, and Shaocheng Ji Are serpentine fault mirrors an indicator of seismic slip? A microstructural analysis ANNUAL BANQUET AND AWARDS (Wilson Hall A/F) SPEAKER: Curt Meine- Adjunct Professor at UW- Madison and Senior Fellow with the Aldo Leopold Foundation and Center for Humans and Nature IMAGINING “CONSERVATION GEOLOGY”: LESSONS FROM THE DRIFTLESS AREA TUESDAY APRIL 25, 2023 8:00 INTRODUCTORY REMARKS AND UPDATES (Wilson Hall B) Rob Lodge and Carsyn Ames, Co-Chairs, 2023 ILSG TECHNICAL SESSION V Session Chair: Allan MacTavish- Consulting Geologist and 2021 Goldich Medalist 8:10 *Justin Jonsson, Pete Hollings, Matthew Brzozowski, Wyatt Bain, and Lionnel Djon Petrogenesis of the mineralized horizons in the Offset and Creek zones, Lac des Iles Complex, N. Ontario 8:30 Pete Hollings, Jacob Hanley, Mark Smyk, Larry Heaman, and Brian Cousens Copper-rich melt inclusions from the St. Ignace Island Complex: Implications for magma mixing and mineralization xxxvii �Proceedings of the 69th ILSG Annual Meeting – Part 1 8:50 Alex Steiner, Dean Peterson, and Gabriel Sweet Magma Recharge and the distribution of Copper and Nickel in the Keweenaw Large Igneous Province 9:10 David Good Identifying regional exploration domains for Ni-Cu-PGE deposit types in the Midcontinent Rift 9:30 Julia Steenburg and Anthony Runkel Record of an Ancient Meteorite Impact Buried Beneath the Twin Cities, MN 9:50 COFFEE BREAK 10:10 Benjamin Drenth, Amy Radakovich Block, George Hudak, Kate Souders, and Stacy Saari Geophysical architecture of the Neoarchean Mentor anorthosite intrusive complex, northwestern Minnesota 10:30 Paul Weiblen The Use of Electric Pulse Disaggregation Technology to Recover Nickel Metal from Nickel Sulfide Ore Deposits 10:50 END OF TECHNICAL SESSION V 11:00 ADDITIONAL POSTER VIEWING – AUTHORS ARE ENCOURAGED TO BE AT THEIR POSTERS (Wilson C & D) 11:30-12:30 LUNCH BREAK - lunches not provided to conference attendees- TECHNICAL SESSION VI Session Chair: Laurel Woodruff- USGS and 2014 Goldich Medalist 12:40 *Margaret Upton, Howard Mooers, and Philip Larson Alteration Geochemistry Characterization and 3D Modeling of the Back Forty Volcanogenic Massive Sulfide (VMS) Deposit Stephenson, Upper Peninsula of Michigan, USA 1:00 Robert Lodge Re-evaluating the tectonics and metallogeny of terranes in the Paleoproterozoic Penokean Orogen, Wisconsin 1:20 William Cannon and Benjamin Drenth Eastward transition from banded iron-formation to ferruginous clastic rocks across the central Upper Peninsula of Michigan 1:40 Jamey Jones, William Cannon, Benjamin Drenth, and Paul O’Sullivan Provenance patterns and tectonic styles of ca. 2.3–1.8 Ga metasedimentary strata in northern Michigan based on regional mapping and detrital zircon U-Pb geochronology xxxviii �Proceedings of the 69th ILSG Annual Meeting – Part 1 2:00 *Audray Hinkemeyer, Howard Moores, and Phillip Larson Determining Provenance of Rainy Lobe Till using Geochemistry and Detrital Zircon Geochronology. 2:20 COFFEE BREAK 2:40 Gordon Medaris Jr. and Steven Driese Secular Changes in the Magnitude of Terrestrial Weathering 2:40 END OF TECHNICAL SESSION VI TECHNICAL SESSION VII Session Chair: Carsyn Ames- Wisconsin Geological and Natural History Survey 3:00 Caroline Rose Tips from a GIS Specialist: Moving maps to GeMS, and a utility for georeferencing quadrangles 3:20 Matthew Rehwald, Carsyn Ames, Sarah Bremmer, William Fitzpatrick, Eric Stewart, Bill Batten, and Stephen Mauel Mobile geologic mapping at the Wisconsin Geological and Natural History Survey 3:40 Roger Schulz Outcrop Scale Mapping Utilizing High-Accuracy GNSS with MnDOT’s Virtual Reference Station (VRS) Network: Minnesota Examples 4:00 Stephen Mauel, Eric Stewart, Matthew Rehwald, Esther Stewart, Carsyn Ames, Sarah Bremmer, and William Fitzpatrick 3D geologic mapping at the Wisconsin Geological and Natural History Survey 4:20 END OF TECHNICAL SESSION VII 4:20 BEST STUDENT PAPER AWARDS STUDENT TRAVEL AWARDS CLOSING REMARKS 4:40 END OF TECHNICAL SESSIONS WEDNESDAY APRIL 26, 2023 8:00am – 5:00pm POST-MEETING FIELD TRIPS Field trips begin and end at The Lismore Hotel 3) Precambrian Geology of the Eau Claire River Valley Rob Lodge and Evan Weber– UW- Eau Claire 4) Quaternary Geology and Geomorphology of the Eau Claire Region Doug Faulkner – UW- Eau Claire J. Elmo Rawling III– Wisconsin Geological and Natural History Survey xxxix �Proceedings of the 69th ILSG Annual Meeting – Part 1 POSTER PRESENTATIONS * denotes a student eligible for Best Student Paper Award. To be eligible students must have graduated no more than one month before the ILSG meeting, be first author, and present the paper at the meeting. *Zsuzsanna P. Allerton, Anita Hall, Françoise Roger, and Christian Teyssier Geochronology and Geochemical Analysis of the Giants Range Batholith in Northern Minnesota Carsyn Ames The Wisconsin Geological and Natural History Survey’s (WGNHS) 2020 and 2021 National Geological and Geophysical Data Preservation Program (NGGDPP) Projects *Ryan Barkley, Noah Phillips, and Pete Hollings The geologic setting, structural controls, and geochemical signature of the Eagle River Au deposit in Northwestern Ontario Marcia Bjørnerud, Buchholz, T., Falster, A.U, And Simmons, W.B. Deformation, metamorphism, fluid flow and pegmatite emplacement history of the post-1630 Ma Waterloo Quartzite of southern Wisconsin Amy Radakovich Block, Kate Souders, Benjamin Drenth, George Hudak, Stacy Saari, and Aaron Hirsch New geologic mapping in the Superior Province of northwestern Minnesota, USA: Pennington and Red Lake Counties *Itai Bojdak-Yates, Marcia Bjørnerud, David Malone, and Esther Stewart A revised provenance model for the Elk Mound Group in south-central Wisconsin based on detrital zircon analysis James DeGraff and William Rose Digital Image Capture and Database Compilation of Historic Mining Data from the Keweenaw Copper District, Michigan: A Progress Update Benjamin Drenth and William Cannon Geophysical mapping of the Great Lakes Tectonic Zone and surrounding Precambrian geology in the central Upper Peninsula, Michigan William Fitzpatrick and Eric Stewart Multiple overlapping features spatially associated with lead-zinc-copper mineralization in the Highland quadrangles, southwest Wisconsin, USA *Lillian Glodowski and Robert Lodge Characterizing volcanic host stratigraphy and syn-volcanic intrusions at the Lynne Zn-Pb-Cu deposit, Oneida Co., Wisconsin xl �Proceedings of the 69th ILSG Annual Meeting – Part 1 *Kaine Johnson and Robert Lodge Hydrothermal Alteration Facies of the Eisenbrey Zn-Cu Deposit, Rusk County, Wisconsin *Matthew Leahy and Robert Lodge Petrology and Geochemistry of the Paleoproterozoic Eau Claire Volcanic Complex, Eau Claire, WI *Francisca Nuñez-Ferreira, Lucas Zoet, and J. Elmo Rawling III Morphometry and formation process of eskers developed under the Chippewa Lobe of the Laurentide Ice Sheet *Jordan Peterzon, Noah Phillips, Peter Hollings and Lionnel Djon Fault zone architecture in mafic protoliths at the Lac des Iles mine, northwestern Ontario Caroline Rose, J. Elmo Rawling III, Eric Carson, John Attig, David Mickelson, William Mode, Mark Johnson, and Kent Syverson Quaternary Geology of Wisconsin at a scale of 1:500,000 (in review) Allison Severson, Eric Nowariak, and Phillip Larson Geology and geochemistry of the basal North Shore Volcanic Group and Midcontinent Rift Intrusive Supersuite, Cook County, MN, USA Eric Stewart, William Fitzpatrick, and Carsyn Ames Relay zones in weakly folded and faulted Paleozoic strata and their role localizing Mississippi Valley-type mineralization, southwest Wisconsin, USA *Madeline Taylor and Marcia Bjørnerud Deciphering the metamorphic and deformational history of the Hardwood Gneiss, Felch District, Michigan: Anomalously high-pressure rocks in the heart of the Penokean orogen *Evan Weber, Robert Lodge, and Jeffrey Marsh U/Pb geochronology and zircon petrochronology of Paleoproterozoic magmas from the Marshfield terrane Penokean Orogen, Wisconsin xli �Proceedings of the 69th ILSG Annual Meeting – Part 1 BANQUET PRESENTATION IMAGINING “CONSERVATION GEOLOGY”: LESSONS FROM THE DRIFTLESS AREA Curt Meine Adjunct Professor at UW- Madison and Senior Fellow with the Aldo Leopold Foundation and Center for Humans and Nature The field of conservation biology emerged in the 1980s when scientists became increasingly alarmed about the loss of biodiversity, and decided that they had a responsibility to put their science to work to address the issue. This required not only new interdisciplinary research, but new ways to put knowledge to work in our human and natural communities. Can we imagine a field of conservation geology that similarly seeks to integrate geological knowledge with history and culture, and addresses our concerns for our landscapes and for future generations? The Driftless Area provides ample examples and opportunities to explore that question. xlii �Proceedings of the 69th ILSG Annual Meeting – Part 1 ABSTRACTS 1 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Geochronology and Geochemical Analysis of the Giants Range Batholith in Northern Minnesota ALLERTON, Zsuzsanna1, HALL, Anita1, ROGER, Françoise2, and TEYSSIER, Christian1 1 Earth and Environmental Science Department, University of Minnesota, 150 Tate Hall, 116 Church St. SE, Minneapolis, MN 55455 2 Géosciences Montpellier, Université de Montpellier-Campus Triolet, c.c. 60 Place Eugéne Batallion 34090, Montpellier, Cedex 05, France The Giants Range Batholith (GRB) is a ~ 2.7-billion-year-old (2.7 Ga) granitic unit in northern Minnesota striking SW-NE from east of Ely to Grand Rapids (Figure 1). It is located N-NW of the 1.8 Ga Mesabi Iron Range and the 1.1 Ga Duluth Igneous Complex (DC). During emplacement, the GRB was situated at the southern edge of the Superior Craton, the Archean core of the North American Continent. At its eastern end the GRB is in contact with the Mesoproterozoic DC (1.1 Ga), which is the intrusive segment of the Mid-continent Rift System, and to the west the GRB flanks the Lower Member of the Ely Greenstone Formation. This project has two main goals: (1) better understanding the origin of the GRB; and (2) using the GRB to track the thermal and hydrothermal history of the rocks from the contact with the DC outward. The project included the compilation of existing data, such as geochronology and geochemistry, that have been collected to date on the GRB, based Figure 1. Simplified geologic map of Minnesota's arrowhead on Allison (1925), Griffin & Morey (1969), region showing the Giants Range Batholith in blue. Prior Viswanathan (1971), Boerboom & Zartman studies have been done in the area circled in red. The white dashed box shows the current and proposed area of this (1993), Boerboom (1994), and Southwick project. Modified from Jirsa, M.A., Miller jr., J.D., & Morey, (1994). The Minnesota Geological Survey G.B. (2008). (Jirsa, 2016) acquired U-Pb zircon age dates on selected samples. Only Boerboom & Zartman (1993) and Boerboom (1994) have completed trace element analysis. Their eight samples are from the central section of the GRB (red circle in Figure 1) and were collected along the northern margin. The samples from the GRB main body have not been analyzed for trace elements, and geochronological data are scarce. Our sampling campaign so far has concentrated on the northeastern part of the GRB (white dashed box in Figure 1) and builds on the work of Boerboom & Zartman (1993) and Boerboom (1994). Thin sections were cut and used in transmitted-light petrography to determine mineralogical composition, analyze textures, and identify accessory minerals for radiometric dating. Radiometric dating involved Laser-Ablation Inductively Coupled Plasma Mass-Spectroscopy (LA-CPMS) performed at the University of Clermont-Ferrand, France. We obtained zircon and titanite age dates for samples located within 1000 meters from the DC contact. The zircon grain separates from one sample produced a concordant age date of ~ 2690 ± 10 Ma. In-situ zircon analysis of another sample displays some discordia (Pb loss) that may be associated with hydrothermal alteration related to DC emplacement. The mounted titanite grains and in-situ analysis yielded ages (approx. 2450-2500 2 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Ma) that are consistently younger than zircons from the same samples. Current and future work include further sample collection in the study area (white dashed box in Figure 1) to obtain additional U-Pb dates on titanite and zircon to the thermal and hydrothermal history of GRB at the contact with the DC. The GRB samples also contain abundant apatite grains, some primary and some recrystallized, that will be dated using the U-Pb method to provide new data on the thermal and hydrothermal history of the GRB near the DC contact. Additionally, we will pursue acquiring bulk composition and trace element data in order to better understand the source of magma and the likely tectonic setting in which the GRB was emplaced. References Allison, I.S., 1925. The Giants Range Batholith of Minnesota. The Journal of Geology, 33(5): 488-508. https://doi.org/10.1086/623215. Boerboom, T.J. and Zartman. R.E., 1993. Geology, Geochemistry, and Geochronology of the Central Giants Range Batholith, Northeastern Minnesota. Canadian Journal of Earth Sciences, 30(12): 25102522. https://doi.org/10.1139/e93-217. Boerboom, T., 1994. Short Contributions to the Geology of Minnesota: Alkalic Plutons of Northeastern Minnesota; Report of Investigations 43. Minnesota Geological Survey, ISSN 0076-9177. Frost, B.R. and Frost, C.D., 2008. A geochemical classification for feldspathic igneous rocks. Journal of Petrology 49.11. Griffin, W.L. and Morey, G.B., 1969. Geology of the Isaac Lake Quadrangle, St. Louis County, Minnesota. Published in Cooperation with Minnesota Department of Iron Range Resources and Rehabilitation. Minnesota Geological Survey 5 P-8 Special Publication Series. University of Minnesota. Southwick, D.L., 1994. Short Contributions to the Geology of Minnesota: Assorted Geochronologic Studies of Precambrian Terranes in Minnesota: A Potpourri of Timely Information. Report of Investigations 43. Minnesota Geological Survey, ISSN 0076-9177. 3 �Proceedings of the 69th ILSG Annual Meeting – Part 1 The Wisconsin Geological and Natural History Survey’s (WGNHS)’s 2020 and 2021 National Geological and Geophysical Data Preservation Program (NGGDPP) Projects AMES, Carsyn1, GOTTSCHALK, Brad1, ROSE, Caroline1, SIBLEY, Dave1 1 Wisconsin Geological and Natural History Survey, University of Wisconsin- Madison, 3817 Mineral Point Rd. Madison, WI 53705 The Wisconsin Geological and Natural History Survey (WGNHS) received grants from the United States Geological Survey (USGS)’s National Geologic and Geophysical Data Preservation Program (NGGDPP) for FY2020 and FY2021. This program promotes the preservation and public accessibility of geoscience collections and data. Projects completed during the 2020 grant were 1) to preserve 130 boxes of hand samples, and 2) to convert 10 WGNHS maps to the standard Geologic Map Schema (GeMS) format. The majority of hand samples for this project came from a donation by Gene LaBerge (UW-Oshkosh) who worked extensively in and around Marathon County, and whose work resulted in a Marathon County bedrock map (LaBerge and Myers, 1983) published by WGNHS. The collection includes more than 1500 specimens from 583 separate outcrops. Successfully preserving these samples is of importance as Marathon Co. continues to urbanize and many of the outcrops these samples represent are being demolished due to land development. The 10 maps converted to GeMS format during the project include Pleistocene maps from northwestern Wisconsin and bedrock maps from southern and northeastern Wisconsin. Converting legacy maps to GeMS format is important because the digital use of WGNHS maps allows for wider and broader use by both internal and external stakeholders. Additionally, a survey of WGNHS external partners showed that a majority prefer digital versions of maps and data. Projects for the 2021 grant included 1) expanding the WGNHS data viewer’s capacity to deliver photos of bedrock cores, 2) digitizing borehole data from the Mineral Development Atlas (MDA)- a joint project between the USGS, United States Bureau of Mines (USBM), and state surveys of Wisconsin, Iowa, and Illinois- that gathered information related to metallic mineral exploration and mining in the lead-zinc district, and 3) photograph, log, and permanently archive seven cores from the Lynne Deposit, a volcangenic massive sulfide deposit in Oneida County. WGNHS’s data viewer, created in 2018, saw its capacity expanded to include photos of cores in their collection. The 2021 project used almost 300 donated Wisconsin Department of Transportation (WisDOT) cores to test pilot this new ability and results are available here: https://data.wgnhs.wisc.edu/data-viewer/. An additional part of this project included the correlation of 3300 scanned logs to the boreholes and updating location data for logs and cores. The MDA portion of the 2021 project focused efforts on mine workings in Lafayette Co., WI. Staff at the Survey geolocated more than 17,000 boreholes and corrected polygons for surface workings such as quarries, prospecting sites, and lead diggings. Lastly, WGNHS permanently archived seven cores from the Lynne Deposit, Oneida Co., WI in 2021. These cores were transferred to WGNHS’s samples repository from the University of Wisconsin- Eau Claire where they had been stored temporarily for student study. The cores (totaling approximately 2500 ft) were then logged and photographed by UW-Eau Claire students. These photos were also added to the WGNHS data viewer. References LaBerge, G., and Myers, P., 1983. Precambrian Geology of Marathon County, Wisconsin. Wisconsin Geological and Natural History Survey IC45: 1-88. https://wgnhs.wisc.edu/catalog/publication/000295/resource/ic45. 4 �Proceedings of the 69th ILSG Annual Meeting – Part 1 The geologic setting, structural controls, and geochemical signature of the Eagle River Au deposit in Northwestern Ontario BARKLEY, Ryan1, PHILLIPS, Noah1, HOLLINGS, Pete1 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada The Eagle River orogenic gold deposit is hosted in the Mishibishu greenstone belt of the western Superior craton, approximately 50 km west of Wawa, Ontario. The deposit, an active underground mine, has been in continuous production since 1995 and produced 1.485 (Moz) of Au through to the end of 2021 (SRK, 2022). The average grade is 9.7 g/pt and Au is primarily hosted in highly strained, milky white to grey quartz veins that dip to the north and strike east to west. The shear zones are hosted in an elliptical quartz diorite pluton, extending into iron rich mafic volcanic rocks. The Mishibishu greenstone belt is dominated by granitic plutons, mafic to felsic volcanics, and lesser amounts of metasedimentary packages. U-Pb zircon dates in the belt range from 2.6 to 2.8 Ga, indicating a Neoarchean environment (Keller, 1989). To understand the geological setting, structural controls, and the geochemical signature of the Eagle River deposit, we completed detailed structural field mapping, petrography, and whole rock geochemistry analysis of the rocks in and around the deposit. A total of 41 whole rock geochemistry samples were collected from the area north of the mine. Two suites were identified; suite one consists of calc-alkaline basalt, andesite, dacite, rhyolite, diorite, tonalite and granite. This suite is characterized by enriched La/Smn ratios of 2.06 to 6.83 and negative Nb anomalies (Nb/Nb* of 0.09 to 0.43), consistent with magmas formed in a supra-subduction environment. Suite two consists of tholeiitic basalt, andesitic-basalt and gabbro. This suite is characterized by flatter trace element patterns with La/ Smn ratios of 0.83 to 1.48 and minor Nb anomalies (Nb/Nb*of 0.40 to 0.85), consistent with primitive arc tholeiites (Fig. 1). Figure 1. Primitive mantle normalised diagrams for the calc-alkaline (blue) vs tholeiitic (red) rocks of the study area. Normalising values from Sun and McDonough (1989). Shear zones for this study appear to be ductile. The white to grey, boudinaged quartz veins are highly strained and flattened, indicating a ductile environment. Gold accumulates in areas of high strain. Quartz veins exhibit chessboard extinction patterns and lobate grain boundaries indicating that the veins have recrystallized through grain boundary migration dynamic recrystallization (Fig. 2; Stipp et al, 2002). Deformation therefore occurred at high temperatures in a low stress environment. 5 �Proceedings of the 69th ILSG Annual Meeting – Part 1 0.5 cm Figure 2. Recrystallization of quartz veins via grain boundary migration. References Keller, J., 1989. The evolution of the Mishibishu greenstone belt, near Wawa, Ontario. Electronic Theses and Dissertations. Stipp, M., Holger & Heilbronner, R., & Schmid, S., 2002. Dynamic recrystallization of quartz: Correlation between natural and experimental conditions. Geological Society London Special Publications. 200: 171-190. 10.1144/GSL.SP.2001.200.01.1. Sun, S.S., and McDonough, W.F., 1989. Chemical and Isotopic Systematics of Oceanic Basalts: Implications for Mantle Composition and Processes. In: Saunders, A.D., Norry, M.J., Eds., Magmatism in the Ocean Basins, Geological Society, London, Special Publications, 42: 313-345. S.R.K Consulting, 2022. 43-101 Eagle River Mine, Ontario, Canada, Wesdome Gold: 262. 6 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Interpreted geophysical cross-sections through the Lake Superior region: Investigating three billion years of geologic history in sixteen lines of data BEDROSIAN, Paul A.1, GRAUCH, V.J.S.1, WOODRUFF, Laurel G.2, CANNON, William F.3, DRENTH, Benjamin J. 1, STEWART, Esther K. 4, PETERSON, Dana E.1 and JONES, James V.5 1 U.S. Geological Survey, Building 20, MS 964, Denver Federal Center, Denver, CO 80225 U.S. Geological Survey, 2280 Woodale Drive, Mounds View, MN, 55112 3 U.S. Geological Survey, 12201 Sunrise Valley Dr., MS 954, Reston, VA 20192 4 Wisconsin Geological & Natural History Survey, 3817 Mineral Point Road, Madison, WI 53705 5 U.S. Geological Survey, 4210 University Drive, Anchorage, AK 990508 2 The northern midcontinent is a window into an Archean-Proterozoic continent, and the Mesoproterozoic Midcontinent Rift System (MRS) that nearly tore it apart. This complex tectonic collage has been largely unmodified during the last billion years yet is poorly exposed except in the Lake Superior region. The area is rich in mineral resources, including native and sedimentary copper deposits, iron formations, volcanogenic massive sulfide deposits, and nickel-copper-platinum-group element sulfide mineralization. In 2016, 2,710 line-km of airborne electromagnetic (AEM) and magnetic data were collected along sixteen regional transects spanning parts of three states and more than three billion years of geologic time (Bedrosian, 2019). The transects range from 100 to 300 km in length and cross parts of the Wisconsin Magmatic Terrane, the Penokean fold and thrust belt, the MRS, and the Archean Superior Province (Figure 1). Data modeling was challenging due to poor control on system height and the prevalence of induced polarization effects (Bedrosian et al., 2018). The final electrical resistivity models derived from the AEM data have been translated into interpreted geophysical cross-sections though an iterative, consensus building approach. A team was assembled with varied expertise in the geology, geophysics, and mineral resources of the MRS, Penokean, and Archean assemblages within the region. Over a period of two years, a series of interpretation sessions worked line-by-line through the transects, culminating in a workshop to synthesize and finalize interpretations. Geologic maps, potential-field data, and drill hole logs were examined alongside the AEM resistivity models and incorporated into the resulting interpretations. Constraints from seismic reflection and refraction studies, magnetotelluric models, geochronology, and detrital zircon studies were also considered where available. The resulting annotated geophysical cross-sections are a resource to be drawn and built upon for geologic and tectonic investigations. Some aspects these sections touch upon include: • Internal structure of the Animikie basin and the basal contact of the Duluth Complex • Geometry and deformation of MRS-flanking sedimentary basins • Structure of the MRS Ashland syncline • Geometry and extent of post-magmatic MRS clastics (Oronto and Bayfield Groups) • Geometry, internal variability and provenance of the Jacobsville Sandstone • Geometry and extent of Archean, Penokean, and MRS faults • Extent and dismemberment of Penokean-deformed metasedimentary units • Iron formations and Penokean structures along the early Proterozoic gneiss dome corridor • Patterns of reverse polarity dikes • Phanerozoic cover and underlying structure (e.g., eastern arm of the MRS) • Distribution, thickness, and variability in glacial cover 7 �Proceedings of the 69th ILSG Annual Meeting – Part 1 New insights and refinements are many but include (a) a restricted areal extent for Bayfield Group clastic rocks, (b) multiple distinct subunits within the Jacobsville sandstone, (c) a close stratigraphic relation between Penokean iron formations and conductive sulfide-rich metasediments, and (d) complex deformation and alteration of the main bowl Animikie basin. Figure 1. Location of AEM and magnetic profiles (magenta). Background geology is from a USGS MRS GIS compilation from published sources of the region. References Bedrosian, P.A., 2018. Geologic mapping and tectonic structure of the U.S. midcontinent via reconnaissance AEM, 7th Intl. Wksp on Airborne Electromagnetics, Kolding, Denmark: 4. Bedrosian, P., 2019. Multi-scale AEM and MT mapping of the Precambrian in Upper Michigan, Northern Wisconsin, and Eastern Minnesota, in Puumala, M., (ed.), Institute on Lake Superior Geology Proceedings, 51st Annual Meeting, Nipigon, Ontario, Part 1 - Abstracts and Proceedings. v.65, Part 1: 67. 8 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Deformation, metamorphism, fluid flow and pegmatite emplacement history of the post-1630 Ma Waterloo Quartzite of southern Wisconsin BJØRNERUD, M.1, BUCHHOLZ, T. 2, FALSTER, A. U.3, and SIMMONS, W. B.3 1 Geosciences Department, Lawrence University, Appleton Wisconsin 54911 1140 12th Street North, Wisconsin Rapids, Wisconsin 54494 3 Maine Mineral & Gem Museum, PO Box 500, 99 Main Street, Bethel, Maine 04217 2 The Waterloo Quartzite, one of the upper Paleoproterozoic ‘Baraboo Interval’ quartzites of the southern Great Lakes region (Medaris et al., 2003), experienced a more complex structural history and higher-grade metamorphism (amphibolite facies) than any of the other quartzite units in this group. It is also distinctive in being intruded by bodies of granitic pegmatite. Natural outcrops of the Waterloo quartzite are limited, but a major quarry near the town of Waterloo (43.210 N, 88.450 W) provides three-dimensional exposures and access to a large volume of fragmented rock. This study is based on observations and samples taken at the quarry over several years as it was deepened and enlarged by blasting. The youngest detrital zircons in the Waterloo Quartzite date to 1634 Ma, younger than the 1710 Ma maximum depositional age of the Baraboo Quartzite, and an indication that sediment transport directions changed from southward to northward (modern coordinates) between the times of deposition of the Baraboo and Waterloo units (Schwartz et al., 2018). The protolith of the Waterloo quartzite was primarily pure quartz sandstone but also included pelites and quartz pebble conglomerates with clasts of jasper (Stewart, 2021). The earliest deformational feature in the Waterloo quartzite is a penetrative foliation (S1) defined by aligned grains of sub-mm muscovite in the pelitic layers; this muscovite has yielded an 40 Ar/39Ar age of 1452 +/- 7 Ma and has been interpreted as evidence of a pervasive fluid flow event that introduced potassium into the supermature sediments, in which K was originally absent (Medaris et al., 2003). In the quarry, the S1 foliation is nearly parallel to bedding; both surfaces strike toward the northeast (045° to 055°) and dip moderately (35°-55°) southeast, suggesting that the rocks lie on the SE limb of a tight NW-verging anticline. In places, mm- to cm-scale quartz veins with Ti-rich hematite masses on their margins lie parallel to the foliation and have fibers oriented perpendicular to the foliation. This points to another episode of fluid infiltration under a stress regime distinct from the one that formed the foliation. These early quartz veins are commonly folded and/or boudinaged. The S1 foliation is overprinted by porphyroblasts of andalusite, typically about 0.5 cm in size. Most of these have been altered to muscovite and/or kaolinite, indicating another episode of fluid infiltration. The kaolinite occurs mainly on the margins of the andalusite crystals, giving them a zoned appearance. In many specimens, the retrograded andalusites have a rusty red color that may be related to the presence of hematite in the kaolinitic rims (Geiger et al., 1982). The next structural feature to develop in these rocks are kink-like crenulations in pelitic horizons, seen abundantly in blocks in the quarry waste piles. At two sites where this crenulation cleavage (S2) was observed in place, it strikes N to NNW and dips steeply east. The geometry of the crenulations is strongly influenced by the presence of the andalusite porphyroblasts/ pseudomorphs, many of which have small, asymmetric pressure shadows of quartz and muscovite that seem to be related to the development of the crenulations. Sometime after the formation of the crenulation cleavage, the quartzite was intruded by Kfeldspar-dominated pegmatite dikes ranging in width from 1 cm to 3 m. Pegmatites have been known from the NW portion of the Waterloo Quarry for some years and have been discussed by 9 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Buchholz et al. (2016). The pegmatite dikes have sharp boundaries and granitic textures, with Kfeldspar, quartz and muscovite crystals of equal and uniform size. Blasting of a phyllitic horizon in the NE part of the quarry has recently exposed additional thin (< 5 cm wide) pegmatite dikes, with mmscale chilled margins at contacts with the host rock. Heavy mineral separates from these thin dikes contain fluorapatite, monazite-(Ce), ilmenite, columbite-(Mn), tantalite-(Mn), evidence of significant enrichment of Ta/Nb and Mn/Fe. In addition to the pegmatite dikes, coarse-grained pegmatite-like patches occur in the necks of boudinaged quartz veins and quartzose layers enclosed by phyllites, primarily in the NE corner of the quarry. Unlike the clearly igneous dikes, these patches have irregular boundaries with the host rock and their crystal size is variable. In thin section, K-feldspar and quartz in these patches show a micrographic texture. Muscovite in pelitic layers surrounding the boudins is coarser than in the rest of the rock, and rusty andalusite pseudomorphs are smeared and flattened in the vicinity of the boudins, suggesting that they had already been altered and softened by the time the boudins formed. Although they occur in the same area of the quarry, the pegmatite-like boudin patches do not seem to be physically connected to the pegmatite dikes. The patches are presumably older since they formed during the process of boudinage, while the dikes apparently postdate deformation. The pegmatite-like material in the boudin necks could either be hydro- thermal or produced by in situ melting related to influx of fluids or perhaps a local drop in pressure (mean stress) during boudinage. Examination of heavy mineral separates from the pegmatite-like bodies associated with boudins revealed fluorapatite and monazite-(Ce). One specimen of the boudin material contains small beryl crystals in a pocket-like void. This may be similar to beryl occurrences in regionally metamorphosed rocks in Austria (Franz et al, 1986), believed to have formed between 500- 550⁰C -- slightly higher than maximum metamorphic temperature estimates of 500⁰C for the Waterloo rocks (Medaris et al., 2003). Small crystals of greenish to light brown dravitic tourmaline are also present locally; analysis shows that these are Li-bearing, as are nearby muscovites. Additional mineral phases include chloritoid, spessartine garnet, fluorapatite, and gahnite, all pointing to the introduction of fluids with a rich mix of ions. Although the Waterloo quarry lies only 20 km in the across-strike direction from the south limb of the Baraboo syncline, it is not easy to correlate either the chronology or the orientations of structures at Waterloo with those in the more famous Baraboo Quartzite. Our observations from the Waterloo quarry suggest that the 1470-1450 Ma “Baraboo Orogeny” (Medaris et al., 2021) was a complex, multistage tectonic event whose details have not yet been fully documented. References Buchholz, T.W., Falster, A.U. & Simmons, W.B., 2016. Second Foord Pegmatite Symposium: 22-23. Franz, G., Grundman, G., & Ackermand, D, 1986. Tschermaks Min. Pet. Mitteilungen, 15: 167-192. Geiger, C., Guidotti, C. & Petro, 1982. Geoscience Wisconsin 6: 21-40. Medaris, L.G. & others, 2003. Journal of Geology, 111, doi:10.1086/373967 Medaris, L.G. & others, 2021. Geoscience Frontiers, 12, doi: 10.1016/j.gsf.2021.101174 Schwartz, J.J., Stewart, E.K. and Medaris, L.G., Jr., 2018. ILSG Proceedings, 64: 93–94. Stewart, E.K., 2021. Wisconsin Geological & Natural History Survey Map 508. Stewart. E.K., Brengman, L. & Stewart, E.D., 2021. Journal of Geology, 129, doi:10.1086/713687. 10 �Proceedings of the 69th ILSG Annual Meeting – Part 1 The Midcontinent Rift System: Neither triple junction nor failed rift? BLEEKER, Wouter1, SMITH, Jennifer1, HAMILTON, Michael2, KAMO, Sandra2, HOLLINGS, Pete3, EASTON, Michael4, and CUNDARI, Robert5 1 Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0E8; wouter.bleeker@canada.ca Jack Satterly Geochronology Lab., University of Toronto, 22 Ursula Franklin St., Toronto, ON M5S 3B1 3 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 4 Ontario Geological Survey, 933 Ramsey Lake Road, Sudbury, ON P3E 6B5 5 Ontario Geological Survey, 435 James Street South, Thunder Bay, ON P7E 6S7 2 The Midcontinent Rift System has often been described in terms of i) a failed intracontinental rift system; with ii) a basic ‘triple junction’ architecture, the three arms of the triple junction being represented by the SW arm of Lake Superior, the SE arm of Lake Superior, and a less developed rift structure reaching up into the Lake Nipigon area. Here we challenge both views. Although it is certainly true that on a local scale, i.e. the North American midcontinent, the rift system failed and inverted, it is likely that on a more global scale the system did not fail but led to ocean opening at ca. 1103 Ma, i.e. the waning phase of the “Early Magmatic Stage”3 of the Midcontinent Rift. This led to a global reorganization of plate stresses. The majority of robust structural indicators suggest that this early stage rifting, initiated at ca. 1110 Ma and waning towards ca. 1103 Ma, was oriented on an NW-SE axis or trend (present orientation), from Lake Nipigon to the SE arm of Lake Superior and beyond. The significant gradient in rifting and lithospheric stretching, from Lake Nipigon (minor rifting followed by sagging) to the SE rift arm (major rifting), requires that the rotation pole for this early phase of rifting was situated to the northwest, somewhere in northwest Ontario. At larger distances from this rotation pole, up to 90° of arc away(?), to the southeast (present orientation), lithospheric spreading may have reached ~1000 km and thus likely led to ocean opening. This early phase of rifting with its NW-SE axis came to a close with a marked hiatus of ~4-5 Myr (the “Magmatic Hiatus”), represented in most sections by a distinct unconformity of conglomerates and more shallow dipping basalt flows on top of older, more steeply dipping basalt flows. When rifting resumed, after this significant hiatus, it opened up the SW arm of the Midcontinent Rift organized on a SW-NE trending rift system. This phase was accompanied by the “Main Magmatic Stage” and was initiated at 1099-1098 Ma, the emplacement age of the Duluth Complex (e.g., Paces and Miller, 1993). The marked gradient in rifting and lithospheric stretching on this SWNE rift system, with major crustal stretching in the central part of Lake Superior, and less stretching farther to the southwest, indicates that the rotation pole for this younger phase of rifting was situated well to the southwest, perhaps in Texas or on the future western margin of Laurentia. This SW-NE rift system shows marked jogs, and may have stepped over to the south, through the eastern arm of Lake Superior, and continued to the northeast in the area now obscured by final accretion and collision of the Grenville orogen at ca. 1 Ga. As for the first phase of rifting, we observe locally (in North America) only one proximal end (relative to the rotation poles) of the larger rift systems—systems that may well have been global in scale. Clearly the later SW-NE rift system is distinct from the earlier NW- SE rift system, with completely different rotation poles, and rift axes that are essentially perpendicular to each other. Relevant to the early NW- SE rift phase, the extent of the rifting and the location of its rotation pole, are occurrences of carbonatite complexes in northwest Ontario, and large diabase sills at the base 3 We use here the magmatic stage terminology of Miller and Nicholson (2013) but with modified age boundaries. 11 �Proceedings of the 69th ILSG Annual Meeting – Part 1 of the Athabasca Basin (the Moore Lakes sills), the latter with an age exactly equivalent to those of the Nipigon diabase sills (see Bleeker et al., 2020 and references therein). At a larger scale, there are 1108 Ma magmatic provinces on several other continents (e.g., the Umkondo sills in South Africa; Hanson et al., 2004). And relevant to the younger SW-NE rift phase is the major diabase sill magmatism of the SW USA Diabase Province at 1095-1085 Ma (e.g., Bright et al., 2014; Heaman and Grotzinger, 1992). Clearly, we need to zoom out to develop a broader understanding of the Midcontinent Rift System and see it in a more global context. The GSC-funded project to refine our knowledge of this major rift system started with an attempt to better define the ages (both precision and accuracy) of some of the major events and many of the mineralized intrusions. We currently have ~30 U-Pb samples in various stages of progress and some early results were reported in Bleeker et al. (2020) and Smith et al. (2020). Several others will be discussed as part of this presentation. Our initial focus was to resolve many of the problematic age ‘outliers’, the majority of which were based on extrapolations from sparse and discordant data. Most of these outliers are now gone. Based on our current data and review of the published literature, major age divisions may be summarized as follows: Initiation: ca. 1111-1110 Ma, as best defined by the large Echo Lake subvolcanic layered intrusion (a robust zircon age, reported in Cannon and Nicholson, 2001). Early Magmatic Stage: 1110-1103 Ma, with emplacement of regional diabase sill complexes (ca. 1108-1106 Ma) following early rift intrusions and regional plateau basalt building (1110-1107 Ma). The Tamarack intrusion, still organized on a NNW-SSE dyke-like system, is ca. 1104 Ma. Hiatus: 1103-1099 Ma, in many places marked by an angular unconformity. Main Magmatic Stage: 1099-1092 Ma, initiated with emplacement of the Duluth Complex and later characterized by the very extensive flood basalts of the Portage Lake Volcanic Group. Late Magmatic Stage: 1092-1084 Ma, waning volcanism and intercalated rift-fill sediments. Sagging and Rift-Fill Stage: 1084 to ca. 1060 Ma, final rift fill sedimentation, Oronto Group. References Bleeker, W. et al., 2020. The Midcontinent Rift and its mineral systems: Overview and temporal constraints of Ni-Cu-PGE mineralized intrusions. GSC Open File 8722: 7–35. DOI: org/10.4095/326880. Bright, R.M. et al., 2014. U-Pb geochronology of 1.1 Ga diabase in the southwestern United States: Testing models for the origin of a post-Grenville large igneous province. Lithosphere, 6:135–156. Cannon, W.F. and Nicholson, S.W., 2001. Geology map of the Keweenaw Peninsula and adjacent area. U.S. Geological Survey, Geological Investigations Series, Map I-2696, scale 1:100 000. Heaman, L.M. and Grotzinger, J.P., 1992. 1.08 Ga diabase sills in the Pahrump Group, California: Implications for development of the Cordilleran miogeocline. Geology, 20: 637–640. Miller, J.D. and Nicholson, S.W., 2013. Geology and mineral deposits of the 1.1 Ga Midcontinent Rift in the Lake Superior region – An overview. Precambrian Research Center Guidebook 13-1:1–50. Paces, J.B. and Miller, J.D., 1993. Precise U‐Pb ages of Duluth complex and related mafic intrusions, northeastern Minnesota: Geochronological insights to physical, petrogenetic, paleomagnetic, and tectonomagmatic processes associated with the 1.1 Ga midcontinent rift system. Journal of Geophysical Research: Solid Earth, 98: 13 997–14 013. Smith, J.W. et al., 2020. Timing and controls on Ni-Cu-PGE mineralization within the Crystal Lake Intrusion, 1.1 Ga Midcontinent Rift. GSC Open File 8722: 37–63. 12 �Proceedings of the 69th ILSG Annual Meeting – Part 1 New geologic mapping in the Superior Province of northwestern Minnesota, USA: Pennington and Red Lake Counties BLOCK, Amy Radakovich1, SOUDERS, A. Kate2, DRENTH, Benjamin J.3, HUDAK, George J.4, SAARI, Stacy M. 5, HIRSCH, Aaron C.1 1 Minnesota Geological Survey, 2609 Territorial Road, St. Paul, MN 55114 U.S. Geological Survey, PO Box 25046, MS 963, Denver Federal Center, Denver, CO 80225 3 U.S. Geological Survey, PO Box 25046, MS 973, Denver Federal Center, Denver, CO 80225 4 Natural Resources Research Institute, 5013 Miller Trunk Highway, Duluth, MN 55811 5 Minnesota Department of Natural Resources, 1525 3rd Ave E, Hibbing, MN 55746 2 The Earth Mapping Resources Initiative (Earth MRI) is a partnership between the USGS and state geological surveys/science agencies that funds data collection and geologic mapping in order to better characterize areas of potential critical mineral resources. Earth MRI recently funded a highresolution airborne geophysical survey (Allen Langhans and Drenth, 2023; Fig. 1, blue box) and acquisition of new geochronologic (Souders, A.K., in review), petrologic, and geochemical data in a part of the Superior Province in northwestern Minnesota that is prospective for numerous criticalmineral-producing systems. Previous geologic mapping of the area (Jirsa et al., 1999; Jirsa et al., 2011) was limited by an absence of outcrop, limited drill hole data, and only one geochronologic age. Newly acquired data support ongoing bedrock mapping across a large area (Fig. 1, red box); This map highlights the geology of Pennington and Red Lake Counties (Fig. 1, orange box). The map area comprises three conterminous subprovinces of the Archean Superior Province which are situated in unusually close proximity to one another; in the map area, the Quetico metasedimentary province pinches to as little as 5 km of thickness in map view where it separates the Wabigoon and Wawa volcanoplutonic subprovinces on either side. Ages from a biotite tonalite in the Snake River batholith (ca. 2758 Ma), a diorite in the Grygla pluton (ca. 2771 Ma), and a biotite-hornblende tonalite in the Red Lake Falls pluton (ca. 2701 Ma) (Souders, in review) define multiple Neoarchean episodes of intermediate to felsic intrusive activity within the Wabigoon subprovince. Interpretation of the improved aeromagnetic data suggests a revised, more southerly position of the Wabigoon-Quetico subprovince boundary, as well as modifications of numerous other geologic contacts across the map area. Finally, new geochronologic ages confirm an Archean (ca. 2737 Ma) age for the Mentor Anorthosite Intrusive Complex (MAIC) (Souders, in review), and new geophysical interpretations reveal that the MAIC is as much as twice as large and much more structurally complex than previously thought (Drenth et al., this volume). Both findings regarding the MAIC are consistent with what is known of other Archean anorthosites in the Superior Province (Sotirou & Polat, 2020; Polat et al., 2018). Work in the larger Earth MRI mapping area is ongoing. Additional geochronologic data will shed light on the depositional history and timing of mineralization of volcanic strata in both the Wawa and Wabigoon subprovinces. Geochemical analyses will supplement petrographic observations and help refine tectonic provenance of all rock units. A new geologic map of the entire area (Fig. 1, red box) will be completed, and a comprehensive mineral potential model will better assess the potential for critical minerals in the area. 13 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Pennington Red Lake Figure 1. Generalized subprovince map of the Superior Province in northwest Minnesota, USA, showing the location of both the recent geophysical survey (blue outline), ongoing new mapping (red outline) for the EarthMRI project, and the map area for this poster (orange outline). References Allen Langhans, A.D., and Drenth, B.J., 2023. Airborne magnetic and radiometric survey, northwestern Minnesota, 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P97D2JJE. Drenth, et al., this volume. Jirsa, M.A., Chandler, V.W., and Runkel, A.C., 1999. M-092 Bedrock geologic map of northwestern Minnesota. Minnesota Geological Survey. Retrieved from the University of Minnesota Digital Conservancy, https://hdl.handle.net/11299/973. Jirsa, M.A., Boerboom, T.J., Chandler, V.W., Mossler, J.H., Runkel, A.C., and Setterholm, D.R., 2011. Geologic map of Minnesota, bedrock geology: Minnesota Geological Survey State Map S-21, scale 1:500,000. Polat, A., Longstaffe, F.J., and Frei, R., 2018. An overview of anorthosite-bearing layered intrusions in the Archaean craton of southern West Greenland and the Superior Province of Canada: implications for Archaean tectonics and the origin of megacrystic plagioclase: GEODINAMICA ACTA, v. VOL. 30, NO. 1: 84–99, https://doi.org/10.1080/09853111.2018.1427408. Sotiriou, P., and Polat, A. 2020. Comparisons between Tethyan anorthosite‐bearing ophiolites and Archean anorthosite‐bearing layered intrusions: implications for Archean geodynamic processes: Tectonics, v. 39, 35. Souders A.K., in review. U-Pb Geochronology of the Mentor Anorthosite Intrusive Complex (MAIC) and Regional Plutonic Units. U.S. Geological Survey Data Release. https://doi.org/10.5066/P9WMD477. 14 �Proceedings of the 69th ILSG Annual Meeting – Part 1 A revised provenance model for the Elk Mound Group in south-central Wisconsin based on detrital zircon analysis BOJDAK-YATES, Itai S.1, BJØRNERUD, Marcia1, MALONE, David H.2, and STEWART, Esther K.3 1 Department of Geosciences, Lawrence University, Appleton, WI, 54911, United States Department of Geography, Geology, and the Environment, Campus Box 4400, Illinois State University, Normal, IL, 61790, United States 3 Wisconsin Geological and Natural History Survey, 3817 Mineral Point Rd, Madison, WI, 53705, United States 2 The Late Cambrian Elk Mound Group consists of three sandstone formations deposited in a shallow tropical sea: the Mount Simon, Eau Claire, and Wonewoc formations, in ascending order. The formations underlie much of the upper Midwestern United States in vast, thin sheets, which thicken toward the Illinois Basin further south. These formations have long fascinated geologists due to their extraordinary physical and chemical maturity, but they have often eluded explanation thanks to those same qualities. Recent studies have employed detrital zircon (DZ) U-Pb analysis to constrain the sources of the sand, and workers have begun to build regional provenance models that describe the origins of the sand and the routes it took to arrive at its present location. Our study builds upon these models with new samples from the Mount Simon Sandstone, a quartz arenite deposited in terrestrial and shoreface environments (Dott et al. 1986). We analyzed samples from outcrops of nonmarine deposits high on the Wisconsin Arch near Wisconsin Dells, WI, as well as a drill core taken 26 miles east of the Dells (the Triemstra core, near Belle Fountain, WI). We place these samples in the context of previous DZ work in this area, especially a study by Konstantinou et al. (2014). The formations of the Elk Mound Group are poorly defined in central Wisconsin, and the samples reveal a transition from Mesoproterozoic source provinces towards Late Archean source provinces as one moves up section and to the west (Figure 1). This transition is understood to represent a shift from sediments derived from the more local Wolf River Batholith (ca. 1470 Ma) and Penokean orogenies (ca. 1830 Ma) to more distal sediments derived from the Superior Province (ca. 2650 Ma). However, other sedimentary basins such as the Animikie and Huronian basins and the Midcontinent Rift may have contributed sediments as well. The physical maturity of the sand grains supports a recycled origin, as multiple cycles of weathering and erosion would have been necessary to produce such rounded grains (Dott, 2003). Sedimentological details of the sandstone reveal additional information about shifts in provenance. A pair of samples from the Wisconsin Dells area (upper Chapel Gorge and lower Mirror Lake) show relatively high proportions of Penokean-age sediments. The sedimentology of the outcrops sampled records a transition from a dune environment to a braided river environment, and these rivers may have brought sediment from the Penokees. Additionally, the proportional increase in Archean-age sediments correlates with a rise in sea level as one rises through the Elk Mound Group. This correlation suggests that local sediment sources were drowned by sea level transgressions, while the distal Superior Province remained high enough to continue eroding and contribute sediment to a shallow sea already rich in Archean-age sand. Paleocurrent indicators derived from optical borehole image logs from wells across central Wisconsin add to the regional provenance picture with evidence of predominant currents flowing toward the west and southwest, giving some indication of the more immediate source and final transport of these sediments. 15 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. DZ data from six samples gathered in central Wisconsin, organized in ascending order through the section and from east to west. (The Triemstra sample is the oldest and furthest east; the Wonewoc sample is the youngest and furthest west.) The Chapel Gorge samples came from the east bank of the Wisconsin River about 1.5 miles north of Wisconsin Dells. The Mirror Lake samples came from the northwest shore of Mirror Lake about 3.5 miles south of Wisconsin Dells. The Wonewoc sample was collected near Wonewoc, WI, about 21.5 miles west of Wisconsin Dells, and was analyzed by Konstantinou et al. (2014). References Dott Jr., R.H., Byers, C.W., Fielder, G.W., Stenzel, S.R., and Winfree, K.E., 1986. Aeolian to marine transition in Cambro-Ordovician cratonic sheet sandstones of the northern Mississippi Valley, USA. Sedimentology, 33: 345-367. Dott Jr., R.H., 2003. The Importance of Eolian Abrasion in Supermature Quartz Sandstones and the Paradox of Weathering on Vegetation-Free Landscapes. The Journal of Geology, 111(4): 387-405. Konstantinou, A., Wirth, K.R., Vervoort, J.D., Malone, D.H., Davidson, C., and Craddock, J.P., 2014. Provenance of Quartz Arenites of the Early Paleozoic Midcontinent Region, USA. The Journal of Geology, 122: 201-216. Lovell, T.R., and Bowen, B.B., 2013. Fluctuations in Sedimentary Provenance of the Upper Cambrian Mount Simon Sandstone, Illinois Basin, United States. The Journal of Geology, 121: 129-154. 16 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Quetico-Wabigoon Subprovince Boundary in the Superior Province north of Thunder Bay, Ontario, Canada BRIGGS, Blaize1, and HILL, Mary Louise1 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada The boundary zone between the Quetico and Wabigoon subprovinces is a complex zone of deformation and metamorphism that historically has been described as a fault, change in metamorphic grade and/or change in lithology. This boundary zone is exposed along Highway 527 within a roughly 23km stretch of highway. At the south end of this zone the DeCourcey Lake outcrop is a strongly foliated, mylonitic gneiss containing quartz, feldspar, garnet, sillimanite, muscovite, and biotite with pegmatites and boudinaged quartz veins that is interpreted to be part of the Quetico subprovince. The north end of the zone is marked by weakly foliated Max Lake conglomerate that displays primary sedimentary textures and is interpreted to be part of the Wabigoon subprovince. Cataclasis was discovered 9.8km north of the DeCourcey Lake outcrop and marks a sharp change from the high-grade amphibolite to granulite facies Quetico lithologies south of the cataclasite to subgreenschist to greenschist facies Wabigoon lithologies to the north. This cataclasite is characteristic of brittle deformation and evidence for a fault that has not been reported in previous studies. The fault is mapped parallel to the foliation of the cataclasite (Fig. 1). This cataclasite is interpreted to be a boundary fault marking the abrupt transition between the Quetico and Wabigoon subprovinces along Highway 527. Figure 1. Map of study area along Highway 527 showing sampled outcrops and new subprovince boundary. Thirteen outcrops along Highway 527 were mapped and sampled for microstructural analysis. 17 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Thin sections created from these samples were used to identify deformation microstructures in quartz and feldspar. Feldspar deformation microstructures are particularly useful and can be used as a proxy for temperature since feldspar needs higher temperatures than quartz to deform internally. Identifying deformation regimes for feldspar is important as most of the rocks within the study area are dominantly composed of quartz and feldspar. Metamorphic Grade Low Temperature 400 ℃ Textures/Deformation Structures -Patchy undulose extinction - Fracturing and cataclasis -Angular grains -Grain size faults with bent cleavage plane/twins Low-Medium 400-500 ℃ Medium 450-600 ℃ High 600 ℃ -Internal fracturing (minor dislocation glide) -Bulging recrystallization (BLG) -Tapered deformation twins -Bent twins -Undulose extinction -Deformation & kink bands -Core & mantle texture -Fine grain recrystallization/uniform grain size -Micro-kinking -Less abundant deformation twins -Sub-grain rotation (SGR) -Bulging recrystallization (BLG) -Core and mantle texture -Myrmekite along foliation planes Table 1. Feldspar deformation structures and corresponding temperatures/metamorphic grade based on descriptions from Passchier and Trouw (2005). References Passchier, C.W. and Trouw, R.A.J., 2005. Microtectonics, Second Edition. Springer. Berlin, New York: 366. 18 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Contributions of diverse mantle sources during the early stages of Midcontinent Rift formation — Implications for a passive rifting model BRZOZOWSKI, Matthew1,2, HOLLINGS, Pete1, ZHU, Jing-jing3, CREASER, Robert4 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada British Columbia Geological Survey, 1810 Blanshard Street, Victoria, BC V8T 4J1 Canada 3 State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 99 Lincheng West Road, Guiyang, Guizhou Province 550081, PR China 4 Earth & Atmospheric Sciences, University of Alberta, 116 Street & 85 Avenue, Edmonton, AB T6G 2R3, Canada 2 It is generally accepted that the Midcontinent Rift System (MRS) and associated magmatism originated as a result of the impingement and melting of the Keweenaw Plume beneath the crust ca. 1.1 Ga (Hutchinson et al. 1990). This interpretation is based largely on Sm–Nd and Re–Os isotope data, and the need for a heat source to explain the large volumes of magma generated (Cannon 1992; Nicholson et al. 1997; Shirey 1997). This view has recently been challenged, however, given the long duration of magmatism associated with the MRS (Hollings and Heggie 2014) and paleomagnetic evidence that is indicative of rapid plate motion during the formation of the MRS (Swanson-Hysell et al. 2014). Alongside these ambiguities are uncertainties in the nature of the sources that fed the MRS with magma (e.g., plume vs. subcontinental lithospheric mantle)? Clarifying these ambiguities has remained challenging given that many of the earliest magmas in the MRS were variably contaminated by crustal material (e.g., the Nipigon sills), masking potential contributions from distinct mantle sources. Development of a robust genetic model for the early history of the MRS and the critical mineral resources associated with this magmatism requires a firm understanding of these contributions. To address this, we integrated new Os isotope data of Initiation (>1,109 Ma), Early (1,109–1,104 Ma), and Hiatus (1,104–1,098 Ma) stage rocks with variations in their bulk-rock trace-element and Nd isotope geochemistry (Brzozowski et al. 2023). Early MRS rock suites are characterized by highly variable γOsi values of -10 to 3857, with Early Stage melts exhibiting the greatest variability (-10 to 3857) and Initiation Stage melts exhibiting the smallest variability (4 to 50). Given that the γOsi values do not correlate with La/Sm, Gd/Yb, and MgO, this variability could not be due to variable degrees of partial melting, retention of garnet in the mantle, or fractional crystallization, respectively. Several of the rock suites of interest exhibit elevated Th/Nb–Th/La and radiogenic εNdi–Sri values that are indicative of crustal contamination and/or contributions from a subcontinental lithospheric mantle (SCLM) source. Based on numerical modeling, the radiogenic εNdi and γOsi values recorded by the mafic–ultramafic intrusions and sills are indicative of their crystallization from hybrid melts (enriched SCLM-derived melt > plume-derived melt) that assimilated <10% crustal material during emplacement (Fig. 1). In contrast, the melts that fed the diabase sills and subaerial lavas likely originated from depleted portions of the Keweenaw Plume based on their variably negative to positive γOsi values, and were contaminated during emplacement (Fig. 1). Although contamination can explain the range of εNdi values exhibited by the rock suites, it cannot independently account for the range of γOsi values because i) this would require unrealistically high degrees of contamination and ii) not all of the rock suites were contaminated (cf. Wolfcamp Basalt). Rather, it is likely that fractionation of sulfide liquid and/or Os-bearing platinum-group minerals also contributed to this variability. Together, these results indicate that i) not all of the rock suites in the MRS crystallized from plume-derived melts, ii) melt contributions from the SCLM were greatest during the early stages of rift formation, and iii) the MRS likely initiated passively, with plume impingement being a coincidence that provided the energy and material necessary for voluminous 19 �Proceedings of the 69th ILSG Annual Meeting – Part 1 magmatism. Figure 1. Variation in γOsi and εNdi in hybrid magmas generated by mixing of melts from various mantle reservoirs. The numbers along the mixing curves are the mixing percents. The numbers in rounded boxes are the εNdi values of the contaminant. References Brzozowski M.J., Hollings P., Zhu J-J., Creaser R.A., 2023. Osmium isotopes record a complex magmatic history during the early stages of formation of the North American Midcontinent Rift — Implications for rift initiation. Lithos: 436–437:106966. Cannon W.F. 1992. The Midcontinent rift in the Lake Superior region with emphasis on its geodynamic evolution. Tectonophysics 213: 41–48. Hollings P., Heggie G. 2014. Rethinking the Midcontinent Rift–puncturing the ‘Plume Paradigm’. In: 60th Institute on Lake Superior Geology. Hibbing, Minnesota, pp 57–58. Hutchinson D.R., White R.S., Cannon W.F., Schulz K.J., 1990. Keweenaw hot spot: Geophysical evidence for a 1.1 Ga mantle plume beneath the Midcontinent Rift System. J Geophys Res 95: 10869. Nicholson S.W., Schulz K.J., Shirey S.B., Green J.C., 1997. Rift-wide correlation of 1.1 Ga Midcontinent rift system basalts: implications for multiple mantle sources during rift development. Can J Earth Sci 34: 504–520. Shirey S.B. 1997. Re-Os isotopic compositions of Midcontinent rift system picrites: implications for plume – lithosphere interaction and enriched mantle sources. Can J Earth Sci 34: 489–503. Swanson-Hysell N.L., Burgess S.D., Maloof A.C., Bowring S.A., 2014. Magmatic activity and plate motion during the latent stage of Midcontinent Rift development. Geology 42: 475–478. 20 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Eastward transition from banded iron-formation to ferruginous clastic rocks across the central Upper Peninsula of Michigan CANNON, W. F.1, DRENTH, Benjamin J.2 1 U.S. Geological Survey, MS 954, Reston, VA 20192; 2U.S. Geological Survey, Denver, CO 80225 The classic Paleoproterozoic iron-formations of the Lake Superior iron ranges are predominantly banded cherty chemical sedimentary rocks characterized by centimeter-scale interbedding of chert and various iron minerals. New observations from legacy iron exploration drill cores that sampled Precambrian rocks below Paleozoic sediments to the east of the exposed iron ranges in the Upper Peninsula of Michigan show that highly ferruginous fine-grained clastic sedimentary rocks are predominant in that area, and that true cherty iron-formation is a subordinate component of the ferruginous sedimentary section. Most of our information is derived from a collection of cores from proprietary exploration holes held by Cleveland-Cliffs Iron Company, who has allowed us to examine, sample, and describe the rock units. Those holes were drilled to test five large-amplitude magnetic anomalies (Figure 1). Cores from four additional anomalies that are publicly available at the Michigan Geologic Sample Repository were also studied. Figure 1. Reduced to pole aeromagnetic anomaly map showing anomalies sourced in sub-Paleozoic Precambrian basement, names assigned to each magnetic anomaly, and drill holes used in this study. Crosshatched pattern is the area of Paleozoic cover. The ferruginous clastic rocks examined in this study are generally laminated at centimeter- to millimeter-scale and range from fine-grained quartzite to siltstone. Most are even-bedded. Laminae alternate between quartzo-feldspathic and ferruginous; some of the latter are nearly 100% iron minerals. Average iron mineral content of individual short core segments is as much as 50% by visual estimates. All are metamorphosed to varying degrees, but unambiguous relict clastic textures are preserved widely. The combination of textures and mineral content leaves no doubt that these are 21 �Proceedings of the 69th ILSG Annual Meeting – Part 1 clastic rocks that accumulated very anomalous concentrations of iron. Figure 2. A. Whole thin section of thinly interlaminated fine sandstone and siltstone from the LaBranch deposit. Light layers are quartzo-feldspathic fine sandstone. Darkest layers are nearly all magnetite. B. Crossed polars view of quartz, microcline, biotite, and magnetite in fine sandstone from the Gladstone deposit. C. Same view as B in reflected light showing numerous magnetite grains. Bright partial rims on some grains are martite. Figure 3. Schematic section of approximately 100 kilometers showing the transition from Vulcan Ironformation in the west, as exposed on the Menominee Range (Bayley et al., 1966) and Felch Trough (James et al., 1961), to ferruginous clastic-dominated sedimentary rocks in areas covered by Paleozoic sediments in the east. We interpret these ferruginous clastic rocks as the lateral equivalent of the Menominee Group, which includes the major banded iron-formations of the Menominee and other iron-ranges of the western Upper Peninsula of Michigan. They record a gradation from the purely chemical and clasticstarved true banded iron-formations to the west, to a more shoreward facies where fine clastic sedimentation predominated and overwhelmed slow precipitation of chert beds. Intermittent periods of diminished clastic input allowed sporadic deposition of layers of cherty banded iron-formation, some of which are granular, indicating deposition in shallow water. These relationships show that the lateral disappearance of true banded iron-formations resulted from suppression of chemical chert precipitation by the input of fine-grained clastic sediments. However, intense iron deposition persisted into this more proximal fine-clastic-dominated facies resulting in abundant ferruginous clastic rocks. References Bayley, R.W., Dutton, C.E., and Lamey, C.A., 1966. Geology of the Menominee Iron-bearing District, Dickinson County, Michigan, and Florence and Marinette Counties, Wisconsin: U.S. Geological Survey Professional Paper 513: 96. James, H.L., Clark, L.D., Lamey, C.A., and Pettijohn, F.J., 1961. Geology of Central Dickinson County, Michigan: U.S. Geological Survey Professional Paper 310: 176. 22 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Workshop Outcomes and Updates for the Minnesota Department of Natural Resource’s Drill Core Library CARTER, Matt J.1 and ELSENHEIMER, Donald2 1 Minnesota Department of Natural Resources, 1525 3rd Ave E, Hibbing, MN 55746 2 Minnesota Department of Natural Resources, 500 Lafayette Rd, Saint Paul, MN 55155 The Minnesota Department of Natural Resources (DNR) provides public access to more than one million meters of drill core from over 9,000 locations across the state at its Hibbing Drill Core Library (DCL). This archive opened in 1967 and has been an invaluable resource for bedrock mapping, mineral exploration, and research, including numerous ILSG presentations. In November 2022, the DNR convened a workshop to gather stakeholder input on DCL policies and procedures (Carter et al., 2023). A need to update these policies and procedures was identified by DNR staff after conducting a 2022 inventory of DCL holdings and determining its current storage capacity, an assessment of projected core submissions, participation in a National Geological and Geophysical Data Preservation Program (NGGDPP) data management workshop, and a review of the policies and procedures of the United States Geological Survey (USGS) and peer repositories. Workshop participants were affiliated with the mining/mineral exploration industry, government agencies, academic institutions, and consulting firms. Feedback was gathered through exercises and participant surveys that focused on the mission of the DCL, prioritization of storage for various materials, sampling and related policies, and desirable enhancements to DCL databases. DNR staff used input from the workshop and reviewed the mission statements from the USGS, the DNR, and peer repositories to create a mission statement for the DCL. DCL curational decisions on what to add or retain in its collection have not previously been constrained by storage capacity. Given anticipated core submissions, participants were encouraged to consider submission and retention priorities, even with a planned addition of a fourth DCL storage building. It was recommended that prioritization should be given to materials that are costlier to replace, are more difficult to access (present and future) as well as complete (i.e., non-skeletonized) diamond drill hole cores that have economic and/or geologic significance. Suggestions were made in favor of retaining pulp and reject samples derived from bedrock core, while acknowledging the potential for the materials to degrade over time. It was suggested that unless surficial materials (e.g., outcrop, glacial sediments) have historical significance or were from areas with restricted access then they should be given a low storage priority. Participants encouraged the DNR to consider strategies that might optimize storage capacity or lower retention costs, such as standardized containers for unconsolidated materials or off-site storage of lower priority samples within the collection. Established DCL policies for facility visits, sampling protocols, and derivative thin sections and dataset submissions are comparable to peer repositories. While reviewing these policies, workshop participants expressed concerns about missing or oversampled intervals and suggested improving communication about the allowable sample size based on the proposed analyses. It 23 �Proceedings of the 69th ILSG Annual Meeting – Part 1 was generally accepted that samples, unused materials, and thin sections should be returned within a year. Yet, it was recognized that multi-year projects may need accommodations, that regular communication and updates must be provided by visitors who want to retain materials for over a year, and that consequences need to be established and enforced for those that do not follow policies. In general, the DCL could improve the communication of its policies to ensure visitors are better able to follow them. Participants also offered ideas on enhancing online access to DCL holdings and associated datasets. These included improving the accuracy of some drill hole collars as well as the link between historical and other publicly available data to drill holes. Digital images of cores boxes were also desirable and the DNR is conducting a pilot program to evaluate digital image collection. The importance of the DCL and the value it offers to researchers, the local mining and mineral exploration community, and the citizens of Minnesota was emphasized by workshop participants. DNR staff are currently using workshop feedback and relevant policies and procedures at peer repositories to make preliminary curational decisions that support the DCL’s mission on topics such as storage prioritization, development of operational policies, enhancements to associated databases, and future decision-making. Discussions and input on preliminary policy ideas at venues such as ILSG will help craft a published update to DCL policies and procedures. References Carter, M.J., Elsenheimer, D. and Arends, H., 2023. Minnesota Minerals Coordinating Committee Drill Core Library Workshop. Minnesota Department of Natural Resources, Lands and Minerals Division, OFR 411: 57. 24 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Digital Image Capture and Database Compilation of Historic Mining Data from the Keweenaw Copper District, Michigan: A Progress Update DeGRAFF, James1 and ROSE, William1 1 Department of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 U.S.A. The Michigan copper rush starting at Copper Harbor in 1843 (Fig. 1) led to 150 years of mining that produced ~7.5 x 106 MT of copper (Bornhorst, T.J. and Barron, R.J., 2011), attracted ~100,000 persons from 40 countries, and profoundly influenced understanding of Lake Superior geology, advances in mining technology, and the region’s pattern of life. Many companies invested significantly in trenching, coring, and mining operations that generated an enormous body of geologic information. USGS efforts in the 1940s and 1950s to map bedrock geology and to assess mineral resources have compiled much of this information as bedrock geology maps with supporting cross sections and reports. Though available online in various formats, these map products are the tip of an iceberg of original detailed source data that is not easily accessed. Significant exploratory drilling that postdates map publication has not been utilized for later geologic investigations because of the same difficulty of access. Paper records and microfiche that decay with time are stored at various locations, which further complicates their use. Many groups could benefit from improved access to this vast amount of information. Therefore, we began a ‘skunk-works’ project to identify and gather information into a digital image repository, to extract it into tabular databases, and to explore how to make it available to scientists, industry, land-use planners, and the general public. Figure 1. Michigan’s copper mining district with generalized bedrock geology. Figure modified from (Bornhorst, T.J. and Barron, R.J., 2011). Numbered field trip stops generally define the extent of copper mining and exploration between 1843 and present. Limited mining also occurred on Isle Royale just off the map to the 25 �Proceedings of the 69th ILSG Annual Meeting – Part 1 north. The initial phase of the project was to identify sources, access data, establish procedures, and demonstrate feasibility. We started with drill holes, trenches, and mine openings posted on USGS geology maps of the Keweenaw Peninsula. Features were symbolized in Google Earth from georegistered maps, assigned unique codes, and recorded with their data in tables having a common layout (Stage 1). Derivative tables contain data unique to a class, such as azimuth and inclination of drill holes found on core logs (Stage 2). Data captured up to this stage are useful for positioning and orienting features on maps and in subsurface models. Stage 3 captures geologic data as a function of location in a feature, e.g., distance along a drill hole. Such information, available from core descriptions at the Keweenaw National Historical Park (Keweenaw National Historical Park, 2016), the USGS/Denver Archives (White, W.S., 1985), old reports and plates, often requires careful transcription to extract it from image records. Other potential sources of such mining data include early reports of the Michigan Geological Survey, university archives, and private collections. Besides preserving and making these data available to others in an easy-to-access format, we hope to build subsurface models that can benefit research, mineral exploration, and land-use planning (Fig. 2). Figure 2. Possible uses of the database once it is further developed. Acknowledgements: We thank Ted Bornhorst (MTU), Jeremy Mason (KNHP), Bill Cannon (USGS), and Jenny Stevens (USGS) for making us aware of and facilitating access to the two archives that currently are being digitally captured and tabulated. This work is possible because of the foresight of many late geologists who gathered and preserved the original paper records. References Bornhorst, T.J. and Barron, R.J., 2011. Copper deposits of the western Upper Peninsula of Michigan, in Miller, J.D., Hudak, G.J., Wittkop, C., and McLaughlin, P.I., eds., Archean to Anthropocene: Field Guides to the Geology of the Mid-continent of North America: Geological Society of America Field Guide 24: 83– 99, doi:10.1130/2011.0024(05). Keweenaw National Historical Park, 2016. Calumet & Hecla Records – 00019/004.02.01.03-007 Microfiche Drill Core Log Library: Calumet, Michigan, U.S. Department of the Interior, National Park Service, on microfiche (accessed August 2016). White, W.S., 1985. “Unpublished diamond drillhole core logs”: U.S. Geological Survey, Field Records Collection, Boxes 282: 287-290. 26 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Geophysical mapping of the Great Lakes Tectonic Zone and surrounding Precambrian geology in the central Upper Peninsula, Michigan DRENTH, Benjamin J.1, CANNON, William F.2 1 2 U.S. Geological Survey, PO Box 25046, MS 973, Denver Federal Center, Denver, CO 80225 U.S. Geological Survey, 12201 Sunrise Valley Dr., MS 954, Reston, VA 20192 The Great Lakes Tectonic Zone (GLTZ) forms the boundary between the Wawa-Abitibi subprovince (north side) and Minnesota River Valley subprovince (south side) within the Archean Superior Province. The GLTZ is concealed for all of its 1100 km length, except south of Marquette in the central Upper Peninsula of Michigan (Sims, 1991; Sims and Day, 1993). Near KI Sawyer, it is exposed as a NW-striking, 2.3 km wide mylonite zone along a strike length of about 11 km, with a mylonitic foliation that dips steeply to the SW (Sims, 1993). The location extent of the GLTZ is unknown to the east where it is concealed beneath Paleozoic sedimentary rocks. We use legacy aeromagnetic data (Daniels et al., 2009) in combination with modern aeromagnetic data (Drenth and Brown, 2020) and ground gravity data to geophysically characterize the GLTZ and map its eastward extent under cover and map additional nearby covered Precambrian tectonic elements. Discontinuous NW-striking aeromagnetic gradients observed over the mylonite zone are interpreted to be produced by structurally juxtaposed rocks with varying magnetizations, and such relations are observed locally in outcrops. Mapping of similar gradients across the region shows that they are widely distributed, but have highest concentration within 3 km of the center of the GLTZ. Gravity data show a steep regional gradient along the GLTZ trend, which is likely produced by the juxtaposition of a dense greenstone belt on the north against lower-density gneisses and granites on the south. Using the distribution of aeromagnetic gradients, broader aeromagnetic patterns, and the regional gravity gradient, the GLTZ is interpreted to extend about 55 km under cover to the east, where it changes to an E-W strike and possibly NE strike (Fig. 1). Interpretations are less detailed and less certain east of the area covered by high-quality aeromagnetic data. Interpreted Paleoproterozoic features have similar strike as the GLTZ. This includes an undated dike swarm and an elongated trough of variably magnetic and dense Paleoproterozoic strata that extends from the Gwinn district southeast under Paleozoic cover. The trough is truncated on its southeastern margin by an interpreted extension of the Norway Lake fault. The GLTZ is terminated on the east by broad aeromagnetic and gravity highs produced by rocks of the buried eastern arm of the 1.1 Ga Midcontinent Rift. The intersection of the rift and the GLTZ is the location of a change in the strike of the rift from crudely N-S north of the GLTZ to NW south of the GLTZ. References Daniels, D.L., Kucks, R.P., Hill, P.L., and Snyder, S. L., 2009. Michigan magnetic and gravity maps and data: a website for the distribution of data: U.S. Geological Survey Data Series 411: http://pubs.usgs.gov/ds/ds411. Drenth, B.J., and Brown, P.J., 2020. Airborne magnetic survey, Iron Mountain-Chatham region, central Upper Peninsula, Michigan, 2018: U.S. Geological Survey data release, https://doi.org/10.5066/P91EF3CI. Sims, P.K., 1991. Great Lakes tectonic zone in Marquette area, Michigan - implications for Archean tectonics in north-central United States: U.S. Geological Survey Bulletin 1904-E: 17. Sims, P.K., 1993. Structure map of Archean rocks, Palmer and Sands 7.5-minute quadrangles, Michigan, showing Great Lakes tectonic zone: U.S. Geological Survey Miscellaneous Investigations Map I-2355, 1:24,000 scale. Sims, P.K., and Day, W.C., 1993. Great Lakes tectonic zone -- revisited: U.S. Geological Survey Bulletin 1904- 27 �Proceedings of the 69th ILSG Annual Meeting – Part 1 S, 11 p. Figure 1. Preliminary interpretations. 28 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Geophysical architecture of the Neoarchean Mentor anorthosite intrusive complex, northwestern Minnesota DRENTH, Benjamin J.1, BLOCK, Amy Radakovich2, HUDAK, George J.3, SOUDERS, A. Kate4, SAARI, Stacy5 1 U.S. Geological Survey, PO Box 25046, MS 973, Denver Federal Center, Denver, CO 80225 Minnesota Geological Survey, 2609 Territorial Road, St. Paul, MN 55114 3 Natural Resources Research Institute, 5013 Miller Trunk Highway, Duluth, MN 55811 4 U.S. Geological Survey, PO Box 25046, MS 963, Denver Federal Center, Denver, CO 80225 5 Minnesota Department of Natural Resources, 1525 3rd Ave E, Hibbing, MN 55746 2 The ca. 2737 Ma (Souders, 2023) Mentor anorthosite intrusive complex (MAIC) lies near the northern margin of the Wawa subprovince of the Archean Superior Province, in an area of northwestern Minnesota where the Wawa, Quetico, and Wabigoon subprovinces are juxtaposed in close proximity (Fig. 1). The rocks of interest are entirely concealed by 10s to >100 m of unconsolidated Quaternary sediments and localized Cretaceous strata and saprolite. The MAIC comprises a large volume of megacrystic anorthosite, with a lesser volume of oxide-rich gabbros. The gabbros are known, from a single borehole intersection at ~70 m depth, to be enriched in vanadium (see http://minarchive.dnr.state.mn.us), and have further potential for chromium and titanium mineralization. New interpretations are based on data from an Earth Mapping Resources Initiative (MRI)-sponsored aeromagnetic survey flown in 2021 and pre-existing ground gravity data, constrained by approximately ten boreholes in the area. The anorthosite is weakly magnetized and dense, with a mean measured density of 2940 kg/m3, producing a 10-60 mGal gravity high. Pervasive epidote alteration is a suggested explanation for the high density of the anorthosite (the density of unaltered anorthite is 2730 kg/m3). The oxide-rich gabbros are strongly magnetized, producing aeromagnetic anomalies as large as 6000 nT, making them readily mappable across the complex. New geophysical interpretations (Fig. 1) suggest that the MAIC is significantly broader in extent than previously interpreted (Jirsa et al., 1999) and can be traced along strike for approximately double its originally interpreted length. The MAIC covers an area of about 640 km2 along a strike length of about 85 km, and forward modeling suggests a depth extent as great as 7 km. The MAIC is here interpreted to be the largest known anorthosite complex in the Superior Province, as measured by preserved extent in map view (cf. Sotiriou and Polat, 2020). The MAIC is observed in drill core to intrude a package of basalt flows at its northwest boundary and is itself intruded by multiple low-density felsic plutons that produce 10-20 mGal, 4-20 km wide gravity lows. The large felsic pluton along the southeastern margin of the MAIC is dated at 2702 ± 6.5 Ma (Souders, 2023), and is here called the Fertile pluton after the nearby town. This tectonomagmatic setting is consistent with other anorthosite complexes of the Superior Province, that commonly intrude packages of mafic volcanic flows and are themselves commonly intruded by felsic plutons (e.g., Polat et al., 2018). Disrupted trends and patterns of geophysical anomalies indicate that the MAIC was variably deformed, likely via both faulting and folding, in a complex fashion. 29 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Preliminary geophysical interpretations of geology surrounding of the Mentor anorthosite intrusive complex and surrounding area. Inset shows location of study area. References Jirsa, M. A., Chandler, V. W., and Runkel, A. C., 1999. M-092 Bedrock geologic map of northwestern Minnesota. Minnesota Geological Survey. Retrieved from the University of Minnesota Digital Conservancy, https://hdl.handle.net/11299/973. Polat, A., Longstaffe, F. J., and Frei, R., 2018. An overview of anorthosite-bearing layered intrusions in the Archaean craton of southern West Greenland and the Superior Province of Canada: implications for Archaean tectonics and the origin of megacrystic plagioclase: GEODINAMICA ACTA, v. 30, 1:84–99. https://doi.org/10.1080/09853111.2018.1427408. Sotiriou, P., and Polat, A. 2020. Comparisons between Tethyan anorthosite‐bearing ophiolites and Archean anorthosite‐bearing layered intrusions: implications for Archean geodynamic processes: Tectonics, v. 39: 35. https://doi.org/10.1029/2020TC006096. Souders A.K., 2023. U-Pb Geochronology of the Mentor Anorthosite Intrusive Complex (MAIC) and Regional Plutonic Units: U.S. Geological Survey data release. https://doi.org/10.5066/P9WMD477. 30 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Multiple overlapping features spatially associated with lead-zinc-copper mineralization in the Highland quadrangles, southwest Wisconsin, USA FITZPATRICK1, William, and STEWART1, Eric 1 Wisconsin Geological and Natural History Survey, University of Wisconsin-Madison Division of Extension, 3817 Mineral Point Road, Madison, WI, 53705 Several features of the Paleozoic bedrock units of the Upper Mississippi Valley (UMV) leadzinc district have been spatially correlated with sulfide mineralization in the Sinnipee Group including folds and faults (e.g. Heyl et al., 1959) and paleovalleys in the base St. Peter unconformity surface (e.g. Mai and Dott, 1985). The significance of these features in creating fluid pathways with sufficient flow to explain the temperature anomalies associated with ore deposition has been justified by the modeling of Arnold et al. (1996). New detailed 1:24,000 scale mapping of two quadrangles in the Highland area created a detailed structural and stratigraphic framework for this area at the northernmost margin of the UMV district, with the results providing a case study allowing the precise geometry of factors such as fold zones and paleovalleys relative to lead zinc mineralization to be revealed. Numerous E-W and N-S trending fold zones with amplitudes of 20-60 ft were identified during mapping of the Highland quadrangles (Fig. 1). Lead-zinc mineralization as defined by the digitized mineral development atlas (MDA) mine maps (Pepp et al., 2019) is clustered on the margins of the synclines, most commonly found on gently sloping ramps below the crest of adjacent structural highs. The largest deposits in the Highland area are spatially associated with pit zones where the base Platteville drops for an additional 40-80 ft below the trough of the synclines over restricted elliptical areas. These pit zones are the site of the steepest folding observed in the mapped area, and may have been important for compromising the integrity of the overlying Maquoketa formation, providing a fluid pathway for migrating brines through this regionally important aquitard (Arnold et al., 1996). Numerous paleovalleys filled with St. Peter formation were identified during mapping (Fig. 2), with the largest in the southeast and southwest corners of the quadrangles mapped continuing down to the Jordan formation with the Prairie du Chien group entirely removed. By removing the Prairie du Chien group, these paleovalleys provide connectivity between the thick, lower Cambrian sandstone aquifer and the upper St. Peter aquifer, allowing large volumes of migrating brines to migrate upward in section towards the favorable ore host units in the Sinnipee Group (Arnold et al., 1996). In the Highland district, the likely flow paths from these paleovalleys to the places where the Maquoketa aquitard was compromised at the pit zones directly correspond to areas with known lead-zinc mineralization. References Arnold, B.W., Bahr, J.M., and Fantucci, R., 1996. Paleohydrology of the upper Mississippi valley zinc-lead district: Society of Economic Geologists Special Publication, no. 4: 378-389. https://doi.org/10.5382/SP.04.28. Heyl, A.V., Jr., Agnew, A.F., Lyons, E.J., Behre, C.H., Jr., and Flint, A.E., 1959. The geology of the Upper Mississippi Valley zinc-lead district: U.S. Geological Survey Professional Paper 309: 310 p., 24 pls., https://doi.org/10.3133/pp309. Mai, H., and Dott, R.H., Jr., 1985. A subsurface study of the St. Peter sandstone in southern and eastern Wisconsin: Wisconsin Geological and Natural History Survey Information Circular 47: 35 p., 2 pls., https://wgnhs.wisc.edu/catalog/publication/000297. Pepp, K., Siemering, G., and Ventura, S., 2019. Digital atlas of historic mining activity in southwestern Wisconsin, 40 p., https://learningstore.extension.wisc.edu/products/digital-atlas-of-historic-miningfeatures-and-potential-impacts-in-southwestern-wisconsin. 31 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. 10ft structure-contour map for the base of the Platteville formation with interpreted fold axes marked by red lines with black outlines with arrows denoting synclines and anticlines. Green polygons mark surface diggings and blue polygons mark underground mine workings from the MDA data digitized by Pepp et al., 2019. Figure 2. Cross section running E-W through the southern part of the Highland quadrangles. Large black arrows mark likely flow paths for mineralizing fluids ascending from St. Peter paleovalleys (Oa) to pit zones which locally breach Maquoketa aquitard. Are serpentine fault mirrors an indicator of seismic slip? A microstructural analysis 32 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Are serpentine fault mirrors an indicator of seismic slip? A microstructural analysis GHANTOUS, Sam1, PHILLIPS, Noah 1, LUSK, Alex 2, NEWMAN, Julie 3, & JI, Shaocheng 4 1 Department of Geology, Lakehead University, Thunder Bay, ON, Canada Department of Geology & Geophysics, Texas A&M University, College Station, TX, USA 3 United States Geological Survey, Denver, CO, USA 4 Department of Civil, Geological and Mining Engineering, École Polytechnique, Montréal, QC, Canada 2 Fault mirrors are smooth, sheened surfaces along a fault plane. An array of microstructures may produce a fault mirror which each have respective formation mechanisms and associated slip velocities. Fault mirrors in certain compositions may be an indicator of ancient earthquakes with seismic slip velocities, but not all fault mirrors are associated with seismic slip. We study the microstructures of two serpentine mirror surfaces, which have not yet been described in the literature, to determine their formation mechanisms and to assess whether they serve as indicators of paleo-seismic slip. One sample is a medium green mirror surface from a late normal fault cutting dunites from the Twin Sisters complex, Washington State, USA. The second mirror surface is pale green and cuts a serpentinite from the Thetford Mines ophiolite in Quebec, Canada. Both fault mirrors have slickenlines on their surfaces indicating that they formed during slip. The mirror surface from the Twin Sisters complex consists of a ~2 micron thick, potentially amorphous, low asperity serpentine layer which may have formed during seismic slip. The mirror surface from the Thetford Mines ophiolite consists of a ~0.5 centimeter-thick layer which is composed of radiating serpentine microcrystallites which are ~ 1 micrometer in length and 10’s to 100’s of nanometers in width. These serpentine microcrystallites are interpreted to have crystallized from a serpentine gel phase during slip. While we hypothesize that these samples are both indicative of seismic slip, similar structures may form if serpentine gels crystallize during aseismic creep. Serpentine fault mirrors may represent paleo-seismic slip, but a microstructural examination of the mirror surface is required to establish a seismic origin. Figure 1. SEM photomicrographs of radiating serpentine microcrystallites from the Thetford Mines ophiolite fault mirror. 33 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Characterizing volcanic host stratigraphy and syn-volcanic intrusions at the Lynne Zn-Pb-Cu deposit, Oneida Co., Wisconsin GLODOWSKI, Lillian N. 1, LODGE, Robert W.D. 1 1 Department of Geology, University of Wisconsin-Eau Claire, 101 Roosevelt Avenue, Eau Claire, WI 54701 The Lynne Zn-Pb-Cu deposit in Oneida County, Wisconsin is one of several volcanogenic massive sulfide (VMS) deposits located within the understudied Paleoproterozoic (1.8-1.9 Ga) Penokean Volcanic Belt (PVB). The PVB formed as the Marshfield and Pembine-Wausau terranes collided and accreted onto the Superior Craton during the Penokean orogeny (Schulz and Cannon, 2007). VMS deposition in Wisconsin has been interpreted to be associated with continental back-arc rifting in a submarine environment. However, little data is available on the deposit-level at Lynne and other deposits in the PVB to test this model. Volcanic and tectonic variability in VMS forming environments and the effect of basement inheritance on metallogeny are important for district-scale exploration. This study constrains the volcanic and tectonic setting at the Lynne deposit via trace element systematics and aims to improve regional metallogenic models in the PVB. Historically, the Lynne deposit was subdivided by Adams (1996) based upon their relative stratigraphic position to the ore horizon into upper and lower “Rhyolite”, “Dacite”, and “Volcaniclastic (VCS)” with mineralized zones occupying the lower VCS unit (Figure 1A). This study relogged seven drill holes from the Lynne deposit and sampled for petrographic and geochemical analyses. The new geochemical data presented in this study reveals there are no petrochemical differences between the upper and lower host strata (Figure 1B). There were also no petrochemical differences observed between the volcanic host rocks and the intruding footwall granodiorite. Therefore, the rocks in this study have been subdivided based simply upon composition and petrography. The volcanic rocks which host the Lynne deposit are comprised primarily of medium to dark grey felsic to intermediate lapilli and crystal tuff. The sedimentary rocks at the Lynne deposit are observed to be very fine-grain, dark grey siltstones with thin parallel laminations and are assumed to be volcanically derived. The Lynne deposit is intruded by a pluton of medium-grained granodiorite which disrupts the lower massive sulfide lenses. The granodiorite appears in a variety of colors ranging from pink and orange to grey and white. Smaller mafic and felsic dikes also crosscut the Lynne deposit. The mafic dikes are dark grey to green with a fine-grain mafic matrix and feldspar phenocrysts. Felsic dikes are commonly light to medium grey with a fine-grain felsic matrix. The geochemical data indicates that VMS deposition at the Lynne deposit occurred in a bimodal-felsic petrochemical assemblage consistent with a continental setting. The shared FII-type lithogeochemistry of the felsic volcanic rocks, granodiorite pluton, and felsic dikes suggests these rocks formed under similar extensional, shallow crustal conditions and originated from the same magmatic system. Combined with the lack of a metamorphic aureole around the pluton, the intruding footwall granodiorite is likely the syn-volcanic intrusion which eventually intruded its own volcanic pile (Galley et al., 2003). Improved geochemical and petrographic data on the Lynne deposit will allow for more accurate and improved models which can be compared to other deposits throughout the PVB and around the world. 34 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. A) Geologic cross section of the Lynne deposit highlighting host stratigraphy, bore hole traces, approximate sample locations, and mineralized zones. Modified from Kennedy (1997). B) Rock type classification diagram of the Lynne. Diagram from Pearce (1996). References Adams, G.W., 1996. Geology of the Lynne base-metal deposit, north-central Wisconsin, U.S.A., in LaBerge, G.L., ed., Volcanogenic massive sulfide deposits of northern Wisconsin: A commemorative volume: Institute on Lake Superior Geology Proceedings, 42nd Annual Meeting, Cable, WI, v. 42, part 2: 161179. Galley, A.G., 2003. Composite synvolcanic intrusions associated with Precambrian VMS-related hydrothermal systems: Mineralium Deposita, v. 38: 443–473. Kennedy, L.P., 1997. Summary geologic and geotechnical report for the Lynne project Oneida County, Wisconsin, U.S.A., Unpublished report of Noranda Minerals Wisconsin Corp.: 26. Pearce, J.A., 1996. A users guide to basalt discrimination diagrams, Trace Element Geochemistry of Volcanic Rocks: Applications for Massive Sulphide Exploration. Geological Association of Canada, Short Course Notes 12: 79-133. Schulz, K.J. and Cannon, W.F., 2007. The Penokean orogeny in the Lake Superior region. Precambrian Research, 157: 4-25. 35 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Identifying regional exploration domains for Ni-Cu-PGE deposit types in the Midcontinent Rift GOOD, David1 1 Department of Earth Sciences, Western University, London, ON N6A 5B7 Canada A new classification strategy for Midcontinent Rift basalts and associated gabbro and ultramafic rocks is proposed, the main objective being to identify magmatic suites associated with known Ni-Cu-PGE occurrences and their spatial distribution across the rift. The study is based on the idea that units with similar incompatible trace element signatures formed under similar conditions in a similar mantle source region and had been subjected to similar contamination or fractionation processes. Elements used in this study are REE, Th, Nb, and Zr. The approach taken is to identify point cloud clusters (magmatic suites) on contoured point density plots for REE represented by ‘lambda’ parameters which emphasize slope and curvature of REE patterns. The resultant groups are checked in Gd/Yb vs. Th/Nb and Gd/Yb vs. La/Sm diagrams which identify influence by crustal contamination or clinopyroxene fractionation, respectively. Melts produced in a metasomatised mantle source are a special case and are distinguished from contaminated melts in a Zr-Th-La diagram. The data set comprises a total of 1815 samples, 343 of which are basalt, from 70 mafic units. Data are carefully screened for discrepancies and extreme outliers removed. Results indicate a total of eight distinct magmatic suites (Groups 1 to 8). The groups are not listed in stratigraphic order because many units appear simultaneously, and a few are active for long time periods during the MCR event. Highlights of the study with respect to Ni-Cu-PGE mineralized intrusions include: a) Group 1 includes the Current, Seagull and Thunder Intrusions and the Lower Suite basalts of the Osler Volcanic Group; b) Group 2 is the most voluminous and includes the Duluth, Tamarack and Crystal Lake deposits, the Pigeon, Cloud and Arrow intrusions, and basalts of the Greenstone Flows, Upper Suite at Black Bay (OVG) and Upper Groups A and B at Mamainse Point; c) The Eagle deposit is intermediate between Groups 2 and 5 but overlaps the field for all flows in Lower Mamainse Point Group A; d) Group 7 includes the Two Duck Lake (Marathon deposit), Abitibi Dykes and metabasalt unit 3a; e) Group 8 includes the Geordie Lake deposit, Wolfcamp basalt, Copper Island dykes and a few of the Pukaskwa dyke swarm; and f) Groups 3 and 4 are not, as yet, associated with mineralized intrusions and includes the Nipigon sills and basalts of the Centre and Upper Suites of OVG. A map of the Midcontinent Rift showing regional domains for each Group is presented, highlighting the extent of igneous rock domains for each of the known Ni-Cu-PGE deposit types, and their locations relative to the central axis of the MCR. 36 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Exploring the geology of the Midcontinent Rift under western Lake Superior using a preliminary velocity model of seismic line GLIMPCE C GRAUCH, V.J.S.1, HELLER, Sam J.2, STEWART, Esther K.3, and WOODRUFF, Laurel G.4 1 U.S. Geological Survey, MS 973, Federal Center, Denver, CO 80225 U.S. Geological Survey, MS 939, Federal Center, Denver, CO 80225 3 Wisconsin Geological & Natural History Survey, 3817 Mineral Point Road, Madison, WI 53705 4 U.S. Geological Survey, 2280 Woodale Drive, Mounds View, MN, 55112 2 Seismic-reflection data were collected in the 1980s as part of the Great Lakes International Multidisciplinary Program on Crustal Evolution (GLIMPCE) to investigate the 1.1 Ga Midcontinent Rift System (MRS). GLIMPCE Line C crosses western Lake Superior from north to south shores (Fig. 1 inset). Many previous workers have interpreted the MRS in Line C as an asymmetric central graben filled with 10–20 km of subaerial basalt flows, overlain by 7-10 km of sedimentary section, and underlain by magmatic underplating. The central graben was interpreted to have formed from extensional normal faults, later reactivated as high-angle reverse faults. The northern part of Line C crosses over a prominent gravity low called the Grand Marais Ridge (GMR; Fig. 1 inset), previously interpreted as an Archean granitic basement high. Line C interpretations are commonly shown on a section plotted against two-way travel time along with a crudely estimated depth scale. We are undertaking a more rigorous approach by developing a detailed velocity model for time to depth conversion. The modeling for Line C is guided by velocities resulting from a pre-existing seismic refraction study, intervals defined by seismic horizons, and correlation with velocity models from neighboring seismic-reflection lines. Velocities are verified using common-reflection point gathers from pre-stack depth migration. Several salient points about the MRS can be gleaned from the preliminary velocity model alone (Fig. 1). The north and south sides of the model are dissimilar, reflecting the disparate geology of the north and south shores. On the south side, we identify an outline reminiscent of a bird (Fig. 1) that helps focus discussion without implying any geologic significance. Aided by a land-based seismic line near the southeast end of Line C, we can tentatively identify the geologic units under the lake within the bird outline (Fig. 1) and interpret a sag basin rather than a graben. The basin contains inferred Porcupine Mountains Volcanics (PM; 6.1 km/s), Portage Lake Volcanics (PLV; 5.9 and 6.5 km/s), with older, possibly reversed magnetic polarity, volcanic units at the base (6.9 km/s). A thick gabbroic sill (6.8 km/s) is inferred within the PLV section. We interpret the truncated PLV (5.9 km/s) and PM (6.1 km/s) intervals at the bird’s head to represent an eroded cliff face of the tilted northern limb of the sag basin. Sheet-like mafic intrusions (7.1 km/s) arise from the lower crust/upper mantle (7.2 km/s) and diverge upwards, following the geometry of the central sag basin. The interpretation that these 7.1 km/s units represent discontinuous or only partially evident magmatic feeder zones is based on their high velocities and sheet-like forms, which in part are constrained by neighboring industry seismic sections. The sedimentary section above the sag basin includes the Oronto Group (3.4, 4.7, 5.2, and 5.6 km/s) and likely Bayfield Group (3.0 km/s). An angular unconformity between Oronto Group (5.6 km/s) and underlying PM (6.1 km/s) at the bird’s head indicates the north limb of the sag basin was tilted prior to deposition. In contrast, the units on the south limb appear conformable. Using aeromagnetic patterns that lead from the north shore into the lake, we tentatively identify a highly reflective (not shown) 4.7 km/s interval as rhyolites of the upper northeast sequence of the North Shore Volcanic Group (NSVG). This unit is interpreted to be angularly unconformable with overlying sedimentary rocks of the same velocity (4.7 km/s). The 5.6 km/s and 6.5 km/s intervals 37 �Proceedings of the 69th ILSG Annual Meeting – Part 1 beneath the interpreted rhyolites are likely older NSVG volcanic rocks that form a carapace over the GMR. The 6.1 km/s velocity of the GMR corroborates its interpretation as a granitic basement high. The model indicates that a 5.6 km/s unit (NSVG?) dives below the bird outline to depths below 15 km. Whether this unit is connected to deeper parts of the sag basin or separated by faulting is obscured by the 7.1 km/s sheet-like intrusions. The sedimentary section on the north side of the model tilts to the south, unconformably overlies volcanic rocks (4.7 and 5.2 km/s) and is truncated by the overlying 3.0 km/s interval (Bayfield Group or equivalent). The sedimentary package on the north side collectively has lower velocities and is thinner than the sedimentary package on the south side. It is unclear if the northern section is correlative with the Oronto Group or represents less consolidated, younger rocks, possibly eroded from the NSVG or basalts at the bird’s head. Identification of velocity intervals and their relations at and under the bird’s head are key to understanding the tectonomagmatic picture but remain somewhat obscure. Suffice to say for Line C that magmatism and syn-magmatic subsidence played a greater role in the origins of the MRS than previously realized. Moreover, unconformable relations within the sedimentary package may be evidence of multiple post-magmatic tectonic events. Figure 1. Preliminary velocity model for GLIMPCE Line C showing velocity intervals in km/s. Inset map shows Line C in relation to the Grand Marais Ridge and neighboring seismic lines in Lake Superior. The white dashed line outlines a bird-like pattern to guide discussion. Velocities near the bird’s head are interfingered only to provide a smooth transition for the depth migration; lines are drawn to better represent the form of the depthconverted seismic horizons, which are not shown for simplicity. Vertical exaggeration=2. 38 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Petrography, geochemistry, and mineralization of the Archean Titan (Roaring River) intrusion, Northwestern Ontario GROENEVELD, Tianna1, HOLLINGS, Peter1, BAIN, Wyatt1, DJON, Lionnel2 1 2 Department of Geology, Lakehead University, 955 Oliver Road Thunder Bay, ON P7B 5E1 Canada, Impala Canada, 69 Yonge Street, Suite 700 Toronto, ON M5E 1K3, Canada The Archean Titan intrusion, formerly known as the Roaring River mafic intrusion, is one of several mafic-ultramafic complexes in northwestern Ontario that are currently the focus of ongoing PGE exploration. The Titan intrusion is located ~145 km North of Thunder Bay, Ontario, in the Winnipeg River terrane of the western Superior Province and is part of the Roaring River Complex (Figure 1). The Titan intrusion was identified as an underexplored area during a lake sediment survey in 2000 (Ontario Geological Survey). In the following five-year period, there were several periods of prospecting and soil surveys carried out in the area as well as one diamond drilling project, which aimed to determine the extent of the Titan intrusion within the Roaring River Complex and assess the potential for economic Ni-Cu-PGE mineralization. This early exploration revealed petrologic and geochemical similarities between the Titan intrusion and the mineralized mafic-ultramafic rocks in the Lac des Iles (LDI) Complex, which lies ~60 km to the south of the Titan intrusion (Figure 1). The LDI Complex is the largest of a series of mafic and ultramafic intrusions known as the LDI suite, all within the Marmion terrane, and hosts the world-class LDI palladium mine. An unpublished U-Pb age for zircons from the Titan intrusion yielded an age of 2690 ± 3.2 Ma, broadly coeval with the LDI Complex, dated at 2689 ± 1.0 Ma (Heaman and Easton, 2006). Outcrop across Titan is sparse, due to the presence of pervasive glacial till and Proterozoic diabase sills. Samples were collected in the summer of 2021 and analyzed for whole rock and PGE geochemistry, sulphur and Sm-Nd isotope analysis, and detailed petrographic characterization. The intrusion consists of a mix of lithologies, ranging from pyroxenites to gabbros to leucogabbros. The lithologies are distributed throughout the intrusion and suggest a simple magma body, where one pulse of magma underwent fractional crystallization within a closed system. Sulphide mineralization is generally confined to pyrite and chalcopyrite, though inclusions of pyrrhotite were observed occasionally. Sulphide mineralization is typically fine-grained and disseminated, though larger blebs do occur, usually of either pyrrhotite or chalcopyrite. The pyrite is considered to be a hydrothermal phase, likely formed from secondary precipitation while the larger blebs of pyrrhotite are considered to be a primary magmatic phase. The Titan intrusion is characterized by enriched LREE’s and fractionated HREE’s, with negative Nb, Zr, Hf, and Ti anomalies (Figure 2). Titan samples have a range of (La/Sm)N from 0.7 to 3.8, a range of (Gd/Yb)N from 2.3 to 7.4, and a range of Nb/Nb* values from 0.02 to 0.47. The geochemistry behavior is consistent with formation in a supra subduction zone setting, which fits with the regional setting of the Winnipeg River and Marmion terranes during this time period (~2.74-2.69 Ga). Only small amounts of crustal material appears to have been incorporated, based on εNd values of 0.70 to 1.82, compared to an estimated depleted mantle at 2.7 Ga which would have a εNd value of +3. Titan appears to be a simple intrusion when compared to intrusions of similar size in the LDI suite and many of the similarities between Titan and the LDI suite appear to occur from regional characteristics of the area in this time period (~2.74-2.69 Ga). 39 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. (left) A regional geology map of the western Superior Province highlighting the approximate locations of the Titan intrusion, the Lac des Iles Complex, and the city of Thunder Bay, modified from Stott et al., 2010. Figure 2. (below) Primitive mantle normalized spider plot, showing representative values for oceanic island basalts (OIB), continental arc, oceanic arc, and the span of values for Titan. Concentrations normalized to primitive mantle from Sun and McDonough (1989) OIB from Sun and McDonough (1989), continental and oceanic arcs from Kelemen et al. (2014). References Heaman, L.M. and Easton, R.M., 2006. Preliminary U/Pb geochronology results: Lake Nipigon Geoscience Initiative. Ontario Geological Survey, Miscellaneous Release-Data 191. Kelemen, P.B., Hanghøj, K., Greene, A.R., 2014. One View of the Geochemistry of Subduction-Related Magmatic Arc, with an Emphasis on Primitive Andesite and Lower Crust. Treatise on Geochemistry, vol. 4: 749-806. Ontario Geological Survey., 2000. Garden-Obonga Lake Area Lake Sediment Survey: Gold and PGE Data; Open File Reports 6028: 76. Stott, G.M., Corkery, M.T., Percival, J.A., Simard, M., Goutier, J., 2010. A Revised Terrane Subdivision of the Superior Province, in Summary of Field Work and Other Activities, 2010. Ontario Geological Survey, Open File Report 6260: 20-1 to 20-10. Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. Geological Society, London, Special Publications, vol. 42: 313-345. 40 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Determining Provenance of Rainy Lobe Till using Geochemistry and Detrital Zircon Geochronology. HINKEMEYER, Audray M.1, MOOERS, Howard D.1, and LARSON, Phillip C.2, O’SULLIVAN, Paul B.3 1 Department of Earth and Environmental Sciences, University of Minnesota Duluth, Duluth, MN 55812 Vesterheim Geoscience, PLC, Hibbing, MN 3 GeoSep Services, 1521 Pine Cone Road, Moscow, Idaho 83843 2 Till of the Late Wisconsin Rainy lobe (RL), which emanated from the Labradoran sector of the Laurentide ice sheet, is exposed at the surface from SW Minnesota to the extreme NE part of the State. The RL advanced to its maximum limit in southwestern Minnesota well prior to the Last Glacial Maximum (ca. 27-30 ka BP) and retreated into Ontario by 17.9 ka BP. This till exhibits dramatic spatial and temporal changes in provenance from the Hewitt till of SW Minnesota to the Independence till in the NE. While texture, fabric, and physical properties are similar, lithologic changes include a decrease in carbonate and greywacke of the Omarolluk Fm. with an increase in mafic rocks of the Duluth Complex as the ice retreated. The observed change in lithology reflects changes in the mean transport length (MTL) of the till. The MTL is the average distance of transport defined by the indicator lithology abundance. The Hewitt till has a mean transport length of > 1000 km, whereas the Brainerd and Independence tills have mean transport lengths of approximately 400 and 100 km, respectively (Berthold, 2015). Two models have been proposed to explain the lithological differences (particularly carbonate) in RL tills. Goldstein (1989) postulated that the downglacier increase in carbonate in the Hewitt till was the result of progressive incorporation, by regelation or deformation, of older underlying till that was rich in carbonate. However, Goldstein also postulated an accretionary origin for the Wadena drumlins, which would imply continuous deposition rather than erosion. This subglacial erosional vs. depositional paradox remains unresolved. Larson (2008) concluded that the changes in sedimentology and landforms record systematic changes in provenance related to changing basal boundary conditions in the interior of the LIS. As the RL advanced early in the last glacial cycle, a continuous till sheet composed of sediment from Hudson Bay and the Hudson Bay lowlands (HBL) extended to SW MN. As the ice approached its maximum limit, much of this till sheet was then eroded exposing Canadian Shield bedrock along the central portion of the flow path (Fig. 1). Early in this phase of glaciation, the sediments reflect long-distance transport from Hudson Bay, and later phases reflect increased proportions of felsic shield lithologies and Duluth Complex rocks. These two models of Rainy lobe till sedimentology are evaluated using mixing models, till matrix geochemistry, and detrital zircon geochronology. The tills underlying the Hewitt till are typically finer textured and contain significant concentrations of Cretaceous age carbonates and shales. Therefore, a multicomponent mixing model is developed to examine sedimentological variability by incorporation of older, underlying tills (e.g. Goldstein, 1989). To evaluate the model of Larson (2008), which implies long vs. short transport distances, twenty-eight samples collected along a transect from SW to NE Minnesota, and six samples collected from the HBL, were processed and sent for geochemical analysis. Fifteen of these samples were processed and analyses for detrital zircon geochronology using laserablation, ICPMS. 41 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Results of a 48-element analytical suite along with latitude, longitude, and depth were run through a principal component. The first 3 factors were retained for analysis. Factors 1 and 3 distinguished mafic vs felsic igneous rock geochemical signatures and carbonate content, respectively. Factor 1, felsic vs. mafic lithologies, can be used as a proxy for MTL and shows locally vs distally derived lithologies. Factor 3 distinguishes tills based on carbonate content. Core SLL (Independence till) plots positively on factor 1 indicating a short MTL. Core CSS (Brainerd till) represents an intermediate MTL, while cores UMRB and TG (Hewitt till) SW of the Wadena drumlin field have the longest MTL. In addition, the samples with the longest MTL plot in high carbonate space, positive on Factor 3. Detrital zircon age populations represented on probability density plots show that the shortest MTL Figure 1. Factor 1 (MTL) vs. factor 3 (carbonate content). samples have the highest signature of local 1.1 Ga MidContinent Rift zircons. A Kolmogorov-Smirnoff (K-S) test statistically compares age populations and determines if they are statistically different. Results from the K-S test reveal that HBL ages are statistically similar to samples from central Minnesota (core CSS). The mixing model, indicates that the Hewitt till is not a mixture low-carbonate RL till and older underlying tills. Geochemistry, and detrital zircon analyses support the model of Larson (2008). Early deposits of the RL in SW Minnesota are geochemically similar to the high-carbonate HBL samples, indicating a distal provenance. This similarity is also observed in the detrital zircon results from the K-S test. Subsequently younger deposits lose the HBL signature and start to incorporate more felsic craton and eventually mafic signatures of the Mid-Continent rift system. References Berthold, A.J., 2015. Surface Boulder Concentrations of the Late Wisconsinan Rainy Lobe, Minnesota, USA. M.S. Thesis, University of Minnesota Duluth: 48. Goldstein, B.S., 1985. Stratigraphy, sedimentology, and late-Quaternary history of the Wadena drumlin region, central Minnesota: Minneapolis, University of Minnesota, Ph.D. dissertation: 216. Larson, P.C., 2008. Quantification of Glacial Sediment Erosion, Entrainment and Transport Processes and Their Implications for the Dynamic History of the Laurentide Ice Sheet. Ph.D. Dissertation, University of Minnesota: 76. 42 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Copper-rich melt inclusions from the St. Ignace Island Complex: Implications for magma mixing and mineralization HOLLINGS, Pete1, HANLEY, Jacob2, SMYK, Mark1,3, HEAMAN, Larry4, and COUSENS, Brian5 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada 2 Department of Geology, Saint Mary’s University, 923 Robie Street, Halifax, NS, B3L 2Y5 Canada 3 Ontario Geological Survey, Ministry of Mines, Suite B002, 435 James St. South, Thunder Bay, ON P7E 6S7 Canada 4 Department of Earth & Atmospheric Sciences, University of Alberta, 126 Earth Sciences Building, Edmonton, AB, T6G 2E3, Canada 5 Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa. Ontario, K1S 5B6, Canada The St. Ignace Island Complex (SIC) comprises volcanic and intrusive rocks that were emplaced the upper portions of Midcontinent Rift-related, ca.1008 Ma Osler Group volcanic rocks (Davis and Sutcliffe 1985; Fig. 1). The St. Ignace Island complex is a ~26 km2 stock with a core of quartz-feldspar-phyric rhyolites and dacites and an outer ring of anorthosite and gabbro (Sutcliffe and Smith 1988; Giguere 1975). The petrology and geochemistry of the SIC has been described by Smyk et al. (2006) and Hollings et al. (2023). The pink to grey, felsic rocks at the center of the complex are quartz-phyric, with rare pyroxene and feldspar phenocrysts. Textures at a variety of scales show evidence of the mingling and mixing of partially crystallized mafic and felsic liquids in SIC rocks. Mafic and felsic liquids may be incipiently mixed, resulting in partially disaggregated mafic enclaves hosted in a felsic matrix. With progressive mixing, the felsic volcanic domains in the rock become darker and phenocrysts of quartz and alkali feldspar appear embedded in the mafic Figure 1. (A) Map of upper Great Lakes. (B) Regional domains. In the most intensely mixed geology of the St. Ignace Island complex. Age data samples, small, mafic crystalline clots are (black stars) from Davis and Sutcliffe (1985) and Davis dispersed throughout a felsic matrix, and as and Green (1997). (C) Geological map of St. Ignace rare mafic enclaves, consisting of only a thin Island, modified after Giguere (1975). rind of mafic rock surrounding coarsegrained plagioclase phenocrysts. Well-preserved silicate melt inclusions (MI), many completely glassy, were observed in quartz, clinopyroxene and some plagioclase phenocrysts from the felsic and mafic rocks of the SIC, representing some of the oldest unrecrystallized silicate melt inclusions recognised to date. Melt inclusions from quartz from the felsic rocks are broadly rhyolitic in composition whereas those from 43 �Proceedings of the 69th ILSG Annual Meeting – Part 1 plagioclase in the mafic rocks range from basalt to basaltic andesite. The melt compositions are interpreted to represent the end-member liquids in the system with direct evidence of mixing of the two. Concentrations of Cu and Ag (in both mafic and felsic MI), and Mo (in felsic MI), are up to an order of magnitude higher in both the mafic and felsic MI than in continental crust and the host bulk rock concentrations. We propose that the melt inclusions have preserved pre-eruptive metal tenors that were subsequently modified by sulfide saturation, degassing, or post-solidus hydrothermal alteration. The elevated Cu and Ag contents are similar to those noted in arc-related and extremely oxidized early Midcontinent Rift-related rocks and may account for the world-class volcano-sedimentary-hosted Cu(Ag) deposits within the Rift as well as the presence of small, porphyry-style deposits. References Davis, D.W., and Green, J.C., 1997. Geochronology of the North American Midcontinent rift in western Lake Superior and implications for its geodynamic evolution; Canadian Journal of Earth Sciences, v.34: 476488. Davis, D.W., and Sutcliffe, R.H., 1985. U-Pb ages from the Nipigon plate and northern Lake Superior; Geological Society of America Bulletin, v.96: 1572-1579. Giguere, J.F., 1975. Geology of St. Ignace Island and adjacent islands, District of Thunder Bay; Ontario Division of Mines, Geological Report 118: 35. Hollings, P., Hanley, J., Smyk, M., Heaman, L., and Cousens, B., 2023. The ~1.1 Ga St. Ignace Island complex, Northern Ontario, Canada: Evidence for magma mixing and crustal melting in the generation of Midcontinent Rift-related bimodal magmas and implications for regional metallogeny. Journal of Petrology, in review. Smyk, M., Hollings, P., and Heaman, L., 2006. Preliminary investigations of the petrology, geochemistry and geochronology of the St. Ignace complex, Midcontinent Rift, Northern Lake Superior, Ontario. In Wilson, A.C. (ed.), Proceedings and Abstracts, Institute on Lake Superior Geology 52nd Annual Meeting, Proceedings Volume 52, Part 1 – Program and Abstracts, 61-62. Sutcliffe, R.H., and Smith, A.R., 1988. Geology of the St. Ignace Island volcanic-plutonic complex; Summary of Field Work and Other Activities, Ontario Geological Survey, Miscellaneous Paper 141: 368-371. 44 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Hydrothermal Alteration Facies of the Eisenbrey Zn-Cu Deposit, Rusk County, Wisconsin JOHNSON, Kaine, P. 1, and LODGE, Robert W.D. 1 1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI This study focuses on the hydrothermal alteration zones surrounding the volcanogenic massive sulfide (VMS) Eisenbrey Zn-Cu deposit in Rusk County, northwestern Wisconsin. The Eisenbrey deposit is hosted within the Paleoproterozoic Pembine-Wausau terrane and is a part of the Penokean volcanic belt, along with many other VMS deposits including the Crandon, Lynne, and Flambeau deposits. The goal of this research is to develop a petrographic and geochemical categorization of alteration types and complete a geochemical mass balance to produce specific alteration trends. Data collected on the hydrothermal alteration at the Eisenbrey deposit is being compared with other Wisconsin VMS deposits to produce a better depositional framework for VMS mineralization. The Penokean Orogen is the culmination of various accretionary events and volcanism. The Penokean Orogen began around 1.88 Ga along the southern margin of the Superior Craton. The collision and subsequent accretion of the Pembine-Wausau terrane resulted in subduction moving to the south and began back arc basin development. Most VMS deposits within the Penokean volcanic belt formed within this back arc extensional environment (Shultz and Cannon 2007). Arc magmatism continued until roughly 1.85 Ga. when an Archean crustal fragment, known as the Marshfield terrane, accreted to the Pembine-Wausau terrane & Superior Craton. VMS systems are characterized by volcanic-sedimentary hosted massive sulfide deposits that form at or near sea floor. Formation is associated with convection of metal rich hydrothermal fluids rising through the crust and mobilizing elements. These deposits are commonly poly-metallic with common mineralization of Zn-Cu-Pb-Ag-Au rich sulfides. Hydrothermal alteration in VMS environments results in mobilization of major elements during modification of primary minerals. The style of alteration varies based on the volcanic setting and fluid chemistry, but commonly are noted by gains in MgO, Fe2O3, K2O, and/or SiO2 and losses in Na2O and CaO (Galley et al., 2007). The Eisenbrey deposit (Figure 1) is relatively poorly understood. Regional metamorphism at the Eisenbrey deposit is lower amphibolite facies and has completely recrystallized the alteration zone at the deposit. Eisenbrey deposit is the only known VMS occurrences associated with Algoma-type iron formation and formed within the “Main Arc Sequence” (DeMatties, 2022). Therefore, improving our understanding of the Eisenbrey hydrothermal system can aid in identifying new exploration criteria in non-typical VMS environments for the Penokean Orogen. Samples of the hydrothermal alteration zone at the Eisenbrey deposit were analyzed across twelve drill holes from both the structural hanging wall and footwall to the ore horizon. These samples were initially divided into alteration mineral assemblages based on petrography. Alteration types include chlorite-cordierite-anthophyllite, quartz-anthophyllite-biotite, quartz-white mica, quartz-biotite. These alteration types were then characterized using major and trace element geochemistry and mass balance calculations. The alteration at Eisenbrey has notable gains in Fe2O3 and MnO; with losses in SiO2, MgO, and Na2O. This contrasts alteration at Flambeau, which has gains in K2O and SiO2 (Lodge et al., 2022). 45 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Representative cross-section of the Eisenbrey deposit with representative photomicrographs of common alteration types (right). I. shows Quartz-Anthophyllite alteration (T-22), II. shows Chlorite-Cordierite alteration (T-40), III. Shows Quartz-White Mica alteration (T-22) References DeMatties, T.A., 2022. Exploration-resource assessment of productive felsic volcanic centers in the paleoproterozoic penokean volcanic belt of northern Wisconsin, Michigan and East-central Minnesota, USA: Ore Geology Reviews, v. 141: 104489. Galley, A.G., Hannington, M.D., and Jonasson, I.R., 2007. Volcanogenic massive sulphide deposits, in Goodfellow, W.D., ed., Mineral Deposits of Canada: A Synthesis of Major Deposit-Types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods: GAC-MAC, Special Publication No. 5: 141-161. Lodge, R.W.D., Lemke, T.C., Blotz, K.E., 2022. Using Ore Petrography and Geochemical Mass Balance to Constrain the Hydrothermal Environment at the Paleoproterozoic Flambeau Cu-Zn-Au Deposit, Wisconsin, USA. Society of Economic Geology, Society of Economic Geologist Annual Meeting Proceedings, Denver, CO, paper P2.15. Schulz, K.J., and Cannon, W.F., 2007. The Penokean orogeny in the Lake Superior region: Precambrian Research, v. 157: 4–25. 46 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Provenance patterns and tectonic styles of ca. 2.3–1.8 Ga metasedimentary strata in northern Michigan based on regional mapping and detrital zircon U-Pb geochronology JONES, Jamey1, CANNON, William F.2, DRENTH, Benjamin J.3, and O’SULLIVAN, Paul4 1 U.S. Geological Survey, Alaska Science Center, Anchorage, AK U.S. Geological Survey, Geology Energy Minerals Science Center, Reston, VA 3 U.S. Geological Survey, Geology, Geophysics, and Geochemistry Science Center, Denver, CO 4 GeoSep Services LLC, Moscow, ID 2 Detrital zircon U-Pb data from ca. 2.3–1.8 Ga metasedimentary successions in northern Michigan are used to test regional stratigraphic correlations and yield key insights into provenance and tectonic styles along the southern Superior craton. Circa 2.3–2.2 Ga Chocolay Group turbiditic strata and quartzite record initial rifting and basin formation along the southern Superior margin. Unimodal ca. 2.7–2.6 Ga age populations were derived from abundant Archean batholiths in the surrounding region. Distinctive ca. 2.3 Ga populations are rare but present in some samples, but the source(s) of these grains is not well understood. Chocolay Group detrital zircon data are very similar to upper Huronian Supergroup strata to the east and with other global ca. 2.3–2.2 Ga glaciogenic successions. The ca. 2.1 Ga Dickinson Group contains bimodal ca. 2.9 and 2.7 Ga age populations in the East Branch Arkose and Solberg Schist that are distinctive in the region and suggest a mixture of recycled 2.3 Ga Chocolay Group quartzite and more diverse regional Archean basement sources. Minor ca. 2.1 Ga grains indicate derivation from nearby plutonic sources or eroded volcanic equivalents of the same age, consistent with magmatism, regional uplift, and final rifting of the southern Superior craton ca. 2.1. After a ca. 100 Ma hiatus, the Ajibik and Siamo Formations of the ca. 1.90–1.85 Menominee Group have unimodal ca. 2.7–2.6 Ga age populations that suggest continued derivation from ca. 2.7– 2.6 Ga batholiths and (or) recycling of older underlying strata. The Goodrich Formation of the basal Baraga Group (ca. 1.85–1.83 Ga) shows similar patterns. A provenance shift to prominent ca. 1.85 Ga populations occurs in turbiditic strata of the Michigamme Formation (upper Baraga Group), indicating arrival of the outboard Wisconsin magmatic terrane to the south. Michigamme strata record basin evolution between the southern Superior Province and the exotic terrane as it approached and collided during the ca. 1.87–1.83 Ga Penokean orogeny, but the relative role of Penokean versus younger ca. 1.78–1.76 Ga tectonism in regional folding and metamorphism remains uncertain. Additional mapping and geochronology focused on Michigamme strata will better constrain regional depositional ages, facies relationships, and tectono-metamorphic patterns. 47 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Petrogenesis of the mineralized horizons in the Offset and Creek zones, Lac des Iles Complex, N. Ontario JONSSON, Justin1, HOLLINGS, Peter1, BRZOZOWSKI, Matthew1, BAIN, Wyatt1, DJON, Lionnel2 1 2 Department of Geology, Lakehead University, 955 Oliver Road Thunder Bay, ON P7B 5E1 Canada Impala Canada, 69 Yonge Street, Suite 700 Toronto, ON M5E 1K3 Canada The Lac des Iles Complex is a Neoarchean (2.69 Ga; D.W. Davis cited in Stone et al., 2003) polyphase mafic-ultramafic complex located in the Marmion terrane of the Superior Province, 85 km north of Thunder Bay, Ontario, Canada. The intrusive complex can be subdivided into two discrete subcomplexes: the ultramafic-dominated North Lac des Iles Complex and the mafic-dominated South Lac des Iles Complex (SLDIC). The SLDIC has been subdivided into four intrusive series, termed the gabbronorite, breccia, norite, and diorite series (Decharte et al., 2018). To date, economic Pd-rich mineralization has been discovered in both the breccia and norite series, and occurs proximal to the contacts between the breccia and gabbronorite series and between the breccia and norite series. The objectives of this study are to i) evaluate the mechanisms of formation of the mineralized horizons near the contact between the breccia and norite domains in the Offset and Creek zones of the SLDIC, ii) evaluate the role that crustal contamination played in this process, and iii) assess the tectonic setting in which the SLDIC formed. The breccia and norite series are both composed of varitextured, brecciated, and equigranular leucocratic-melanocratic norites and gabbronorites, and their altered equivalents. The breccia series contains a greater proportion of brecciated and varitextured rocks, while the norite series contains a greater proportion of equigranular rocks. All pre-alteration lithologies are essentially plagioclaseorthopyroxene cumulates with varyingly minor quantities of interstitial clinopyroxene, biotite, magnetite, chalcopyrite, pentlandite, and pyrrhotite. Variable degrees of hydrothermal alteration are indicated by the presence of tremolite-actinolite and talc (after pyroxenes), chlorite and sericite (after plagioclase), and pyrite (after pyrrhotite). Although the breccia and norite series are mineralogically similar, the breccia series is generally more leucocratic (i.e., higher plagioclase/pyroxene ratio) than the norite series. Neodymium isotopic evidence indicates that the Offset and Creek Zone magmas were crustally contaminated. ɛNd values of 19 analyzed samples range from +0.38 to -3.47 (median = -2.13), which is consistently more negative than the ɛNd value of +2.24 expected in an uncontaminated mantlederived magma that crystallized at 2.69 Ga. The crustal contaminant that imparted the negative ɛNd values is unlikely to be the tonalitic gneiss that hosts the SLDIC, as the ɛNd value of one reported tonalitic gneiss sample is -1.77 (Brugmann et al., 1997). The lack of correlation between ɛNd and geochemical or spatial variations suggests that variable crustal contamination was not the cause of the geochemical variability observed within the Offset and Creek Zones. Samples from both the breccia and norite series have similar trace-element chemistry, including enriched LILE/LREE patterns, flat HREE patterns, and pronounced negative Nb anomalies. Although these characteristics can be caused by assimilation of crustal material, it is more likely that they are the result of formation of the parental magma in a magmatic arc. Evidence for this interpretation includes low Nb/Yb ratios, high Ba/Th ratios, low Th content, and the lack of correlation between geochemical variability and Nd isotopic variability. Evidence from S isotopes of sulfide minerals and whole-rock geochemistry suggests that the addition of crustal S was not necessary in the formation of the Pd-rich mineralization within the Offset and Creek zones. δ34S values of 54 crystals from 17 samples range from -0.37‰ to +3.28‰ VCDT 48 �Proceedings of the 69th ILSG Annual Meeting – Part 1 (median = +1.11‰), with values from 52 of 54 crystals falling in the expected range of mantle-derived sulfur (0 ± 2‰; Seal, 2006). Based on the association of low Cu/Pd ratios with high Pd values, Offset and Creek zone ores formed at high R factors, which were likely high enough to cause the PGE enrichment without incorporation of crustal sulfur. The higher degree of Pd enrichment in the Offset Zone compared to the Creek Zone was likely due to a greater amount of sulfide liquid in the Offset Zone that also underwent higher R factors; the distribution of sulfide liquid and magma flow may have been influenced by primary structural constraints on the geometry of the intrusion. No evidence was found for significant low-temperature remobilization of chalcophile elements, including the PGEs. The compositional variability observed within the breccia and norite domains suggests that both domains formed via multiple pulses of compositionally similar magma. The proximity of mineralization to the interpreted feeder conduits suggests that the distribution of mineralization is largely the result of PGMs/Pd-rich pentlandite crystallizing as the magma transitioned from the feeder structure outwards into the periphery of the intrusive complex. This process may have repeated several times as successive magma pulses infiltrated the partially crystallized intrusive complex, resulting in the redistribution of ores in brecciated zones. References Brugmann, G.E., Reischmann, T., Naldrett, A.J., and Sutcliffe, S.H., 1997. Roots of an Archean volcanic arc complex: the Lac des Iles area in Ontario, Canada. Precambrian Research, vol. 81: 223-239. Decharte, D., Hofton, T., Marrs, G., Olson, S., Peck, D., Perusse, C., Roney, C., Taylor, S., Thibodeau, D., and Young, B., 2018. Feasibility study for Lac des Iles mine incorporating underground mining of the Roby Zone. North American Palladium, NI 43-101 Technical Report: 435. Seal, R.R., 2006. Sulfur isotope geochemistry of sulfide minerals. Reviews in Mineralogy and Geochemistry, vol. 61: 633-677. Stone, D., Lavigne, M.J., Schnieders, B., Scott, J., and Wagner, D., 2003. Regional geology of the Lac des Iles area, in Summary of Field Work and Other Activities 2003. Ontario Geological Survey, Open File Report 6120: 15-1 to 15-25. 49 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Slip Kinematics of the Keweenaw and Hancock Faults within the Midcontinent Rift System, Upper Peninsula of Michigan LANGFIELD, Katherine1, DeGRAFF, James1, GAMET, Nolan1 1 Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, MI, USA The Keweenaw fault is a major compressional structure along the center of the Keweenaw Peninsula and positioned near the southern edge of the Midcontinent Rift System (MRS). The smaller Hancock fault connects with the hanging wall of the Keweenaw fault and, together, the two faults define a thrust slice. The MRS formed ~1.1 billion years ago when a major extensional event split a significant portion of the ancient North American continent across the Upper Midwest. The rifting produced large volumes of basaltic lava, roughly ending with the Portage Lake Volcanics that have an exposed thickness of 3-5 km along the Keweenaw Peninsula (1). A common interpretation of the Keweenaw fault is that it originally formed as a normal fault during MRS extension and then inverted to become a reverse fault during a post-rift compressional event, most likely the Grenville Orogeny (2,3). Another interpretation is that the Keweenaw and Hancock faults are parts of a detached fault system that was initiated during the Grenville Orogeny (4). Until a few years ago, ideas about these and similar faults in the region considered only dip slip with an either normal or reverse sense of motion. Recent bedrock mapping and measurements of faultslip lineations, however, have revealed a significant component of right-lateral strike-slip on the Keweenaw fault system near its northeastern end which is about twice the magnitude of north-side-up reverse slip (5, 6). To clarify the slip kinematics of this region we utilized bedrock mapping and fault slip measurements between Hancock and Mohawk, MI to clarify the geometry and slip kinematics of the NE-trending Keweenaw and Hancock faults and to relate their characteristics here to what is observed along the more easterly trending portion of the fault system previously studied (Fig. 1). Rose diagrams of slickenlines rakes found along the Hancock and Keweenaw Faults show that both faults have roughly equal dip-slip versus strike-slip components (Fig. 2). This bimodal distribution of rake data differs from previous EDMAP projects, possibly due to the overall curvature of the Keweenaw Peninsula. The strike-slip to dip-slip component ratio was 2:1 (Mueller, 2021). The resulting map from this project indicates that the Keweenaw Fault isn’t a single fault trace, but instead connected fault segments (Fig. 3) The updated map and cross-section from this project proposes a new model for the Keweenaw Fault system kinematics. Acknowledgements This project was funded by the U.S Geological Survey’s EDMAP program under Award No. G21AC10681. This funding was matched by the Department of Geological and Mining Engineering and Sciences of Michigan Technological University, as well as sponsorship by the Michigan Geological Survey. Funding was also provided by the ILSG Student Research Fund for work done in the Quincy Mine, as well as an award by the Michigan Space Grant Consortium. Thanks goes to Tom Wright for access to the Quincy Mine. Additionally, we thank Ian Gannon, Breeanne Heusdens, Jack Hawes, Braxton Murphy, and Dillon Breen for fieldwork assistance. 50 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Map showing geology of the Keweenaw Peninsula. The boxes show the areas for the previous and current EDMAP project. (Cannon and Nicholson, 2001). Figure 2. Rake histograms showing the distribution of low and high angle rake on the Keweenaw fault (A) and Hancock fault (B). Arrows indicate mean rake of each dataset. Figure 3. Updated bedrock geologic map and legend of study area. References Cannon, W.F., and Nicholson, S.W., 2001. Geologic Map of the Keweenaw Peninsula and Adjacent Area, Michigan, U.S. Geological Survey, 1:100000 scale. Cannon, W.F., 1994. Closing of the Midcontinent rift ‒ A far-field effect of Grenvillian compression: Geology, v. 22: 155-158. Bornhorst, T.J., 1997. Tectonic context of native copper deposits of the North American Midcontinent Rift System: in Ojakangas, R.W., Dickas, A.B., and Green, J.C. (eds.), Middle Proterozoic to Cambrian Rifting, Central North America: Boulder, Co, GSA Special Paper 312: 127-136. DeGraff, J.M. and Carter, B.T., 2022. Detached structural model of the Keweenaw fault system, Lake Superior region, North America: Implications for its origin and relationship to the Midcontinent Rift System: Geological Society of America Bulletin, https://doi.org/10.1130/B36186.1. Tyrrell, C.W., 2019. Keweenaw Fault Geometry and Slip Kinematics – Bête Grise Bay, Keweenaw Peninsula, Michigan [M.S. thesis]: Houghton, Michigan, Michigan Technological University: 30. Mueller, S.A., 2021. Structural Analysis and Interpretation of Deformation Along the Keweenaw Fault System West of Lake Gratiot, Keweenaw County, Michigan, Open Access Master’s Thesis, Michigan Technological University 51 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Petrology and Geochemistry of the Paleoproterozoic Eau Claire Volcanic Complex, Eau Claire, WI LEAHY, Matthew D.1, LODGE, Robert W.D.1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA 1 The 1.8 Ga Eau Claire Volcanic Complex (ECVC) is located in the northwestern portion of Wisconsin primarily exposed in the Eau Claire River valley. The complex is part of the Marshfield terrane of the Penokean Orogen which developed along the southern margin of the Superior craton (Schulz & Cannon, 2007). Following the accretion of a juvenile ocean island arc, now known as the Pembine-Wausau terrane (PWT), with the southern margin of the Superior craton, opposing subduction zones closed the ocean between the accreted PWT and MT resulting in coeval magmatism on both terranes prior to collision around 1850 Ma. The origin of the MT is uncertain but is believed to be a small Archean craton that is either a rifted fragment of the Superior Province (Zi et al., 2021) or Wyoming Province (Malone et al., 2019). The suture between these terranes is the Eau Pleine Shear Zone. Paleoproterozoic subduction-related volcanism began to develop along MT’s northern margin, resulting in arc volcanism and back-arc spreading with associated calc-alkaline felsic magmas (DeMatties, 2022). This volcanism continued until the terrane collided with the subduction trench, resulting in a major compressional event along the Superior craton (Sims et al., 1989; Shultz and Cannon, 2007). This comprehensive interpretation of the tectonic setting fits well with the eastern portion of the MT where rocks are more abundantly exposed. However, the lack of outcrop exposure due to extensive Cambrian sedimentary strata has restricted research and mineral exploration in western parts of the orogen (DeMatties, 2022). This includes the ECVC, which is based on geophysical data, and has high potential for supergene-enriched VMS-style mineralization (DeMatties, 2022). The main objective of this study is to map and sample volcanic, metamorphic, and intrusive packages of the ECVC exposed along the North Fork of the Eau Claire River (Figure 1A) and Chippewa River for whole-rock geochemistry and petrographic analysis. Trace element geochemical data can be used to determine magmatic and tectonic settings of these rocks and improve regional tectonic models for the ECVC and MT. Twenty-four samples were analyzed for major elements via XRF and trace elements via ICPMS. Rock classifications were given in the field, reevaluated during petrographic analysis, and grouped into suites based on geochemistry. The majority of the suites were separated into four main categories: felsic gneiss (Figure 1B), mafic gneiss (Figure 1C), amphibolite (Figure 1D), and granitoid (Figure 1E). Each suite was diagnosed with a tectonic signature using multiple trace element diagrams. Th/Yb versus Nb/Yb displayed geochemical characteristics of deep crustal recycling for the majority of the samples, related to the active subduction that occurred during the advancement of the MT. The only suite that differs from this trend is the amphibolite group, which has a lower Th-Yb-Nb concentration, insinuating magma-crustal interactions with the protolith basalt. A tectonic classification tertiary diagram using La-Y-Nb solidified the theory that calc-alkaline arc magmatism dominated the MT region, while the amphibolite suite trends towards a more tholeiitic arc composition. This interpretation is backed by a magmatic affinity diagram as well using Th-Yb-Zr-Y percents. 52 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. (A) Regional map of the Eau Claire River with the North Fork and relative location in Wisconsin, (B) Poorly exposed bedrock of a felsic gneiss, (C) Isoclinal folded trondhjemite at Hamilton Falls trending eastwest, (D) Elongated pipe vesicles on an amphibolite outcrop near Knights Pool, (E) Intrusive contact between pegmatite and amphibolite. References DeMatties, T. A. (2022). Exploration-resource assessment of productive felsic volcanic centers in the Paleoproterozoic penokean volcanic belt of northern Wisconsin, Michigan and East-central Minnesota, USA. Ore Geology Reviews, 141, 104489. https://doi.org/10.1016/j.oregeorev.2021.104489 Malone, S.J., Nicholson, K.N., and Dowling, C.B., 2019, Preliminary geochemistry on the Marshfield Terrane, west-central Wisconsin: Geological Society of America Abstracts with Programs, doi: 10.1130/abs/2018am-322316. Schulz, K.J., and Cannon, W.F., 2007, The Penokean orogeny in the Lake Superior region: Precambrian Research, v. 157, p. 4–25, doi: 10.1016/j.precamres.2007.02.022. Sims, P.K., Schmus, W.R., Schulz, K.J., and Peterman, Z.E., 1989, Tectono-stratigraphic evolution of the early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: Canadian Journal of Earth Sciences, v. 26, p. 2145–2158, doi: 10.1139/e89-180. Zi, J.-W., and al., et, 2021, Refining the Paleoproterozoic tectonothermal history of the Penokean orogen: New U-Pb age constraints from the pembine-wausau terrane, Wisconsin, USA: doi: 10.1130/gsab.s.14700069. 53 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Structural analysis and slip kinematics of the Keweenaw fault system between Bête Grise Bay and Gratiot Lake, Keweenaw County, Michigan LIZZADRO-McPHERSON, Daniel1, DeGRAFF, James1, and GANNON, Ian2 1 2 Department of Geological and Mining Engineering Sciences, Michigan Technological University, 630 Dow Environmental Sciences, 1400 Townsend Drive, Houghton, MI 49931 USA The Keweenaw fault is perhaps the most important geologic structure on the Keweenaw Peninsula, with an estimated 7-11 km (1) of reverse slip juxtaposing Cu-bearing volcanic strata of the ~1.1 Ga Portage Lake Volcanics above ~1.0 Ga Jacobsville Sandstone. The fault has been interpreted as a riftbounding normal fault later inverted by compressional pulses of the Grenville Orogeny (2) and, more recently, as part of a detached thrust fault system unrelated to an earlier normal fault (1). The fault is shown on published maps as a nearly continuous fault trace whose sinuosity implies multiple fault segments and complex slip dynamics. Recent mapping has revealed that the Keweenaw fault at its most northeastern exposure on land is better characterized as a network of interconnected, left-stepping fault segments with easterly strike and exhibiting a 2:1 ratio of dextral strike slip to reverse slip (3). This project focused on the eastern half of a 2019-2020 EDMAP project (Fig.1) to map the Keweenaw fault system between Bête Grise Bay and Gratiot Lake. New mapping combined with structural and fault-slip analyses produced a revised bedrock geology map (Fig. 2) and a 3D-model (Fig. 3) that better constrain the geometry of the fault system, revealing folds and fault-bounded blocks in the main fault’s footwall. Analyses of fault slip data indicates a strike-to-dip slip ratio of 1.7:1 and a local shortening direction of 083°-263°. Slip along faults is a function of their strike relative to the shortening direction. Eastward transport of faultbounded blocks relative to the distal footwall was facilitated by mostly strike slip on longer EWtrending faults and reverse slip on shorter NEtrending faults, coupled with layer-parallel detachments along weak layer boundaries. The fault network defines a complex multistranded Figure 1. Bedrock geology of the Keweenaw transpressional system with overall dextral strike Peninsula (4), showing the 2017-2018 (grey box) slip and north-side-up reverse slip. Footwall folds and 2019-2020 (green box) EDMAP study areas. in Jacobsville strata adjacent to mostly strike-slip faults are considered to be cogenetic drag folds that formed during the Rigolet phase of the Grenville orogeny. These findings are consistent with recent mapping projects adjacent to the study area and investigations that relate far-field compressive pulses of the Grenville Orogeny to deformation of Keweenawan strata. Acknowledgements Funding provided by the USGS EDMAP program (Award No. G19AC00140) with a matching contribution from the Department of Geological and Mining Engineering and Sciences, Michigan Technological University and additional support from the Keweenaw Community Forest Company. Sponsored by the Michigan Geological Survey. 54 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 2. Keweenaw fault system between Lac La Belle and Gratiot Lake. Deer Lake fault block is in the Keweenaw fault’s footwall between the lakes. Cross-sections shown by thin black lines labeled A - F. Figure 3. Cross-section B-B' showing modeled hanging-wall and footwall structural and stratal relationships across the Deer Lake fault block. References DeGraff, J.M. and Carter, B.T., 2023. Detached structural model of the Keweenaw fault system, Lake Superior region, North America: Implications for its origin and relationship to the Midcontinent Rift System: Geological Society of America Bulletin, v. 51, no. 1: 449–466. Cannon, W.F., Green, A.G., Hutchinson, D.R. et al., 1989. The North American Midcontinent Rift beneath Lake Superior from GLIMPCE seismic reflection profiling. Tectonics, v.8:305-332. Tyrrell, C.W., 2019. Keweenaw Fault Geometry and Slip Kinematics – Bête Grise Bay, Keweenaw Peninsula, Michigan: Michigan Technological University, M.S. thesis: 30. Cannon, W.F. and Nicholson, S.W., 2001. Geologic Map of the Keweenaw Peninsula and Adjacent Area, Michigan. U.S. Geological Survey, Map I-2696, Scale 1:100,000. 55 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Re-evaluating the tectonics and metallogeny of terranes in the Paleoproterozoic Penokean Orogen, Wisconsin LODGE, Robert W.D.1 1 Department of Geology & Environmental Science, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA The tectonic model for the development of the Penokean orogen was synthesized in a classic paper by Schutz and Cannon (2007) that compiled decades of mapping, sedimentology, U/Pb geochronology, and geophysical surveys. The orogen started at ca. 1880 Ma with the accretion of Pembine-Wausau terrane, an oceanic arc complex, onto the margin of the Superior Province. A subduction flip after accretion resulted in overprinting continental arc volcanism and rifting (Figure 1A) until the collision a collision of an Archean crustal block, known as the Marshfield terrane, at ca. 1850 Ma. Several undeformed intrusions, interpreted as post-tectonic intrusions, constrain the end of the Penokean orogen at ca. 1835 Ma (Figure 1B). Perhaps the most important event during the orogen was the formation of the ~150 million tonnes of volcanogenic massive sulfide (VMS) deposits in the Pembine-Wausau terrane at ca. 1875 Ma (Sims et al, 1989; Quigley, 2016). This event was widespread across multiple VMS deposits. This presents a clear episode of submarine rifting and was assigned to a period of continental back-arc tectonism by Shultz and Cannon (2007). This is supported by the presence of inherited Archean zircons at the Lynne and Back Forty VMS deposits (Quigley, 2016) indicating the presence of Archean crust during the formation of Pembine-Wausau magmas. However, new U/Pb data has documented a second VMS forming event at ca. 1835 Ma at the Back Forty (Quigley, 2016) and Eisenbrey (Weber and Lodge, 2022) VMS deposits. Recognition of this extensional event has led to an alternate tectonic model wherein back-arc extension reactivated multiple times during ridge subduction (Zi et al., 2021). One of the principal issues that needs to be resolved with the classic Penokean tectonic model is the regional setting of Penokean VMS mineralization. VMS deposits formed in continental settings have different petrochemical associations than those formed in oceanic settings. New lithogeohemical data from mafic and felsic rocks at several VMS deposits (Flambeau, Eisenbrey, Lynne, Wolf River) suggest that most of the deposits hosted in rocks that are consistent with oceanic settings, while some suggest a continental setting. This suggests that the continental setting for the VMS mineralization does not apply to all deposits and that the extent of Archean basement needs to be better defined. Zircon petrochronology provides a mechanism to better resolve the nature of continental basement and its influence on metallogeny by providing a link between age of magmatism and tectonic setting and/or crustal inheritance. Once again, some deposits within the Pembine-Wausau terrane provide evidence for Archean basement, while others do not. However, in the process of discovering new ages, we also discovered that VMS forming environments continued until ca. 1835 Ma in a juvenile, oceanic setting. It was also discovered that some of the rocks from the Eau Claire volcanic complex of the Archean Marshfield terrane were mantle-derived, oceanic magmas that were ~1875 Ma with no evidence for Archean inheritance and seems eerily similar magmas from the Pembine-Wausau terrane. While Penokean magmas are known to intrude Archean rocks in the Black River Falls region of Wisconsin (Weber and Lodge, 2022), they clearly show Archean inheritance. As the hunt for domestic critical minerals makes its way to Wisconsin, the Penokean terranes and their metallogenic setting needs to be re-evaluated. 56 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 2. Illustration of tectonic models proposed by Shultz and Cannon (2007) and various new petrochemical or zircon petrochronology datasets that highlight some inconsistencies in the model. REFERENCES Quigley, A., 2016. Setting of the volcanogenic massive sulfide deposits in the Penokean Volcanic belt, Great Lakes region, USA: Unpublished M.S. thesis, Colorado School of Mines: 95. Schulz, K.J., and Cannon, W.F., 2007. The Penokean orogeny in the Lake Superior region: Precambrian Research, v. 157: 4-25. Sims, P.K., Van Schmus, W.R., Schulz, K.J., and Peterman, Z.E., 1989. Tectonostratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: Canadian Journal of Earth Sciences, v. 26: 2145-2158. Weber, E.M., and Lodge, R.W.D., 2022. New U/Pb Geochronology from the Proterozoic Penokean Orogen, Wisconsin: Implications for VMS Metallogeny. Society of Economic Geology, Society of Economic Geologist Annual Meeting Proceedings, Denver, CO, paper P5.10. Zi, J.-W., Sheppard, S., Muhling, J.R., and Rasmussen, B., 2021. Refining the Paleoproterozoic tectonothermal history of the Penokean Orogen: New U/Pb age constraints from the Pembine-Wausau terrane, Wisconsin, USA: Geological Society of America Bulletin, v. 134: 776-790. 57 �Proceedings of the 69th ILSG Annual Meeting – Part 1 3D geologic mapping at the Wisconsin Geological and Natural History Survey MAUEL, Stephen1, STEWART, Eric1, REHWALD, Matthew1, STEWART, Esther K. 1, AMES, Carsyn1, BREMMER, Sarah1, and FITZPATRICK, William1 1 Wisconsin Geological and Natural History Survey, University of Wisconsin-Madison Division of Extension, 3817 Mineral Point Road, Madison, WI, 53705 The Wisconsin Geological and Natural History Survey has constructed a preliminary 14-county 3-D geologic data model across southern Wisconsin. The model was constructed primarily from well construction reports (WCRs) that have been refined for several WGNHS projects, as well as data from the Mineral Development Atlas, borehole geophysics, and data from previous mapping performed at various scales. Well Construction Reports (WCRs) from digital and analog sources were assembled in a GIS geodatabase. The land surface elevation for each well was extracted from a DEM, and the elevation was then used to “hang” each well’s downhole lithology. By displaying and exaggerating the data in 3D, the different lithologies were carefully selected and assigned to geologic formations. Prior to interpolation, statistical outliers were identified, inspected, and edited when appropriate. The elevation for each formation contact was used to interpolate a raster. The resultant raster was inspected to identify obvious outliers, and after the outliers were edited or removed, a “final” raster of each contact was generated. The formation contact rasters can be intersected with a bedrock elevation raster to produce a geologic map. New data can be added to the model when available, and a new updated map can be generated. The products derived from this type of 3D geologic modelling are useful to the public in many applications. Harmful minerals or metals dissolved in groundwater are a realistic concern in Wisconsin, and determining the geologic formation in which a well terminates can help to avoid or resolve water quality issues. 3D geologic modeling can help to inform decision making about land use and land practices, land conservation, zoning and planning, identification of natural hazards, and the construction & engineering of wells, roads, railways, and buildings. 58 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Secular Changes in the Magnitude of Terrestrial Weathering MEDARIS, L. Gordon Jr.1, and DRIESE, Steven G.2 1 2 Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706 Department of Geosciences, Baylor University, Waco, TX 76798 In a recent investigation of paleosols in the Lake Superior region, the magnitudes of weathering in six Proterozoic paleosols were found to be less than those in four Phanerozoic paleosols and four modern soils (Medaris et al., 2022). However, in view of this relatively small database, the apparent age distinction in the magnitudes of weathering might be spurious, and thus we have expanded the database to test the veracity of secular changes in the magnitude of terrestrial weathering. Twenty-one first-cycle paleosols in igneous and metaigneous rocks with well-characterized and relatively homogenous protolith compositions were selected for comparison. These paleosols occur world-wide, vary in age from 100 Ma to 2960 Ma, and have protolith compositions ranging from gabbro to granite. This expanded database confirms that the magnitude of weathering in Phanerozoic paleosols and modern soils is greater than that in Precambrian paleosols. Potassium metasomatism is a common phenomenon in paleosols (Rye and Holland, 1998), and among the 17 Cambrian and Precambrian paleosols investigated here, 14 experienced potassium metasomatism, which is recorded by the presence of neoblastic muscovite, illite, or microcline. The effect of such K-metasomatism is illustrated in a plot of Al2O3-(CaO*+Na2O)-K2O, where compositional trends for modern soils and unmetasomatized paleosols are oriented subparallel to the AC*N join (Fig. 1A), and those for K-metasomatized paleosols are rotated towards the K apex (Fig. 1B). (A) (B) Figure 1. Protolith compositions and paleosol trends in the system, Al2O3-(CaO*+Na2O)-K2O. A: Modern soils and paleosols without K-metasomatism; B. Paleosols with K-metasomatism. In K-metasomatized paleosols, the amount of K2O removed by weathering is unknown, but may be estimated by comparison to an average for the depth variations of K2O and Na2O in modern soils, for which: (% change K2O) / (% change Na2O) = – 1.40z3 + 0.95z2 – 0.31z + 0.75 where z is normalized depth. Following this approach, the removal of K2O is estimated to be 47 ± 4% for the combined Cambrian and Precambrian paleosols and observed to be 54 ± 21% for the Cretaceous paleosols and 47 ± 21% for modern soils (Fig. 2A). Interestingly, no correlation exists between the percentage of K2O removed and age (or protolith composition; not shown). In contrast, the total 59 �Proceedings of the 69th ILSG Annual Meeting – Part 1 addition of K2O to the weathered profiles, expressed in terms of Depth-Normalized Mass Flux, progressively increases with decreasing age, i.e. 0.74 ± 0.29 at 2960 Ma, 0.96 ± 0.18 at 2450 Ma, 1.04 ± 0.52 at 1600-2200 Ma, and 1.62 ± 0.36 at 500 Ma (Fig. 2B). (A) (B) Figure 2. A: Percentages of K2O removed from soils and paleosols; B: Total K2O added to paleosols, expressed as Depth-Normalized Mass Flux (DNMF). The percentage removal by weathering for the sum of SiO2, CaO, Na2O, and K2O(est or meas) progressively increases from Archean (17.3±1.5%) to Proterozoic (21.0±3.7%) to Cambrian (25.1±3.1%) to Cretaceous (37.1±10.8%) paleosols. In comparison, the percentage of mass removed from five modern soils is 36.0±3.7%, which lies within the values for the Cretaceous paleosols. We suggest that the greater magnitude of weathering in Phanerozoic soils compared to Proterozoic ones is due to higher concentrations of organic acids during Phanerozoic soil formation, which resulted from the emergence of sparse cryptophytes in biological soil crusts in Cambrian time and subsequent greening of the continents with vascular plants from Devonian time to the present. Figure 3. Percentages of the total mass of SiO2, CaO, Na2O, and K2O removed from modern soils and paleosols. References Medaris et al., 2022. Journal of Geology, v. 130, in press. Rye & Holland, 1998. American Journal of Science, v. 298: 621-672. 60 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Morphometry and formation process of eskers developed under the Chippewa Lobe of the Laurentide Ice Sheet NUÑEZ-FERREIRA, Francisca1, ZOET, Lucas1, and RAWLING III, J Elmo 2 1 2 Department of Geoscience, University of Wisconsin-Madison, Madison, WI, 53705 Wisconsin Geological and Natural History Survey, University of Wisconsin‐Madison, Madison, WI, 53705 Eskers are an important indicator of paleo subglacial hydrologic conditions and a good alternative to direct glaciological observations because they are one of the few landforms that record those processes. Esker morphology and sedimentology is useful to gain insight into how sediment transport relates to subglacial hydrology along channels, which in consequence provides understanding on ice dynamics. However, large discrepancies in the formation mechanisms of eskers still exist and there are even fewer attempts to investigate the influence of soft bed conditions on this process. To address this, we analyzed the morphometry and distribution of eskers formed under the Chippewa Lobe of the Laurentide Ice Sheet (Figure 1). This includes mapping the sinuosity and spatial distribution with 2m resolution LiDAR, comparing these to sediment thickness derived from a water well data base, and examining the sediment sequence of one large esker exposed to sand and gravel extraction (~20 m tall) (Figure 2). The LiDAR analysis revealed a direct relation between sinuosity and length of eskers formed in soft bed conditions, with a mean of 1.07 that is very similar to eskers formed under hard bed conditions. Eskers spacing over the soft bed of the Chippewa Lobe appear closer than over hard beds in Canada (e.g Storrar et al, 2014). The spacing of eskers decrease when the ice margin retreats, meaning that melt rates increase (Boulton et al, 2009; Hewitt, 2011). Moreover, the relation between the distribution of eskers and till thickness indicates that eskers formed preferentially over thin layers of sediment, specifically near 18 meters for the Chippewa Lobe. The results from the grain size distribution of the large esker showed that the critical shear stress changed nonmonotonically throughout the formation of the esker. As such, we can assume that the water velocity or depth of the channel likely changed sporadically with time while the esker formed. Figure 1. Distribution of eskers formed under the Chippewa Lobe during the Last Ice Age. 61 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 2. Location of the selected esker for sediment analysis. The yellow start shows the location of a pit where the samples were extracted for the analysis. References Boulton, G.S., Hagdorn, M., Maillot, P.B., & Zatsepin, S., 2009. Drainage beneath ice sheets: groundwater–channel coupling, and the origin of esker systems from former ice sheets. Quaternary Science Reviews, 28(7-8): 621-638. Hewitt, I.J., 2011. Modelling distributed and channelized subglacial drainage: the spacing of channels. Journal of Glaciology, 57(202): 302-314. Storrar, R.D., Stokes, C.R., & Evans, D.J., 2014. Morphometry and pattern of a large sample (> 20,000) of Canadian eskers and implications for subglacial drainage beneath ice sheets. Quaternary Science Reviews, 105: 1-25. 62 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Subsurface characterization of the Duluth Complex and related intrusions from 3D modeling of gravity and magnetotelluric data PETERSON, Dana E. 1, BEDROSIAN, Paul A. 1 and FINN, Carol A. 1 1 U.S. Geological Survey, MS 973, Federal Center, Denver, CO 80225 The Mesoproterozoic Duluth Complex and related intrusions in northeastern Minnesota make up the second largest exposed mafic intrusive complex in the world, second only to the Bushveld Complex in Africa. It is one of the major plutonic components of the Midcontinent Rift System and hosts a variety of copper-nickel sulfide and platinum-group-element deposits. Given the complex geology of the area, 3D modeling is necessary to provide a complete picture of the variable densities and geometries of intrusive suites throughout the Duluth Complex as well as their extent at depth. In this study, we use Bouguer gravity data collected over the past ~60 years and magnetotelluric data collected in 2019 to create new 3D models of density, resistivity, and subsurface structure of the region constrained by geologic data. We use the results of these models to calculate the total volume of the Beaver Bay Complex, Duluth Complex, and onshore North Shore Volcanic Group, and estimate preliminary intrusion and emplacement rates using age estimates from Swanson-Hysell et al. (2021). We model both thickness and density of intrusive and volcanic rocks in the region using Oasis GMSYS-3D. The igneous layer in our starting model is 11 km thick with a constant density of 2,941 kg/m3. Other surfaces in the model include topography, near surface glacial deposits, a high-density lower crustal layer, and the base of the crust. We start our inversion by allowing the basal surface of the igneous units to vary and then invert for density within the igneous layer, within a range of 2,630-3,180 kg/m3. Our gravity modeling indicates that intrusive and volcanic rocks reach a maximum thickness ~23 km, or half the crustal column, with densities ranging from ~2,730-3,030 kg/m3 and a mean density of 2,940 kg/m3. The thickest, highest density areas of the model are beneath the Beaver Bay Complex and other mapped diabase intrusions. We interpret the two thickest areas in our gravity model as feeder zones for the Beaver Bay intrusive complex and possibly also for the Duluth Complex, in-line with interpretations arising from previous gravity studies in the area (Allen, 1994; Miller et al., 2002). Preliminary volume estimates from 3D gravity modeling indicate the present-day Duluth Complex, Beaver Bay Complex, and onshore volcanic rocks constitute ~92,100 km3 of igneous material. We calculate the volume of separate mapped units by extending the mapped geologic boundaries at the surface to depth within our 3D model. Three major geologic groups each comprise ~30% of this total volume: 1) the North Shore Volcanic Group, 2) diabase units of the Beaver Bay Complex and intrusions to the northeast and southwest of it, and 3) the Duluth Complex Layered and Anorthositic series. The older Early gabbro series and Felsic series of the Duluth Complex make up the remaining ~10% volume. 206Pb/238U zircon ages for the Anorthositic and Layered series from Swanson-Hysell et al. (2021) indicate that rocks of these units were emplaced contemporaneously over a period of 500,000 ± 260,000 years, suggesting an emplacement rate of ~0.06 km3/year, assuming a constant rate on magma input. Using recently acquired magnetotelluric data, we invert for resistivity in the study area using ModEM (Kelbert et al., 2014). Our magnetotelluric model highlights an arcuate low resistivity anomaly at depths of ~9-20 km, westwardly adjacent to the high-density and high resistivity feeder zones (Figure 1). This anomaly may represent a plane of weakness along which magma intruded to form the Beaver Bay Complex and the Duluth Complex. Low resistivities in this case would be attributed to sulfide or graphitic mineralization that developed along the contact between intruding magma and country rock. These resistivities are also similar to values observed in the Paleoproterozoic metasedimentary rocks of the Animikie Basin, located to the southwest of the Duluth Complex. The 63 �Proceedings of the 69th ILSG Annual Meeting – Part 1 spatial and temporal relationship between the Animikie Basin and Duluth Complex raises a tantalizing hypothesis that the basin structure may have preferentially localized magma intrusion. If this was the case, entrainment of conductive metasedimentary rocks of the Animikie Group along a pre-existing fault could also explain the arcuate low resistivity anomaly observed adjacent to the highly resistive feeder zones. Figure 1. Depth slice through the 3D magnetotelluric resistivity model at ~14 km depth. Black dashed line is the surface extent of the Duluth Complex and related intrusive and volcanic rocks. White lines are 5 km contours of Duluth Complex thickness extracted from our gravity model, starting from 10 km. Cyan line is the outline of Lake Superior. Acknowledgements Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government. References Allen, D.J., 1994. An integrated geophysical investigation of the midcontinent rift system: Western Lake Superior, Minnesota, and Wisconsin. PhD thesis: Purdue University, West Lafayette, Indiana: 267. Kelbert, A., Meqbel, N., Egbert, G.D. and Tandon, K., 2014. ModEM: A modular system for inversion of electromagnetic geophysical data. Computers & Geosciences, 66:40-53. Miller, J.D., Jr., Green, J.C., Severson, M.J., Chandler, V.W., Hauck, S.A., Peterson, D.M., Wahl, T.E., 2002. RI-58 Geology and mineral potential of the Duluth Complex and related rocks of northeastern Minnesota. Minnesota Geological Survey. Retrieved from the University of Minnesota Digital Conservancy, https://hdl.handle.net/11299/58804. Swanson-Hysell, N.L., Hoaglund, S.A., Crowley, J.L., Schmitz, M.D., Zhang, Y., & Miller Jr, J.D., 2021. Rapid emplacement of massive Duluth Complex intrusions within the North American Midcontinent rift. Geology, 49(2): 185-189. https://doi.org/1.1130/G47873.1. 64 �Proceedings of the 69th ILSG Annual Meeting – Part 1 On the Importance of Geologic Maps for Mineral Exploration PETERSON, Dean1 1 Big Rock Exploration, 2505 West Superior Street, Duluth, MN 55806 The basis for most types of geologic investigations is fundamentally rooted in geologists’ observations and interpretations made of landscapes, exposed rocks, and surficial materials in their natural habitat: “in the field”. Coherent geologic maps, which may take many years to create, represent assembled collections of observations in context of space and geologic time, requiring teams of geologists who are usually employed by federal or state/province geological surveys. The outcomes of these concerted efforts in the field are published geologic maps at various scales. It is these works of publicly funded geologic mapping that form the foundation upon which mineral exploration programs and mineral resource developments are built (Figure 1). These early endeavors are key components in national goals to define domestic resources of critical minerals. In decades past, many university geology students in the USA (including the author) were employed as summer interns assisting geological survey geologists in the bedrock geologic mapping of 1:24,000 scale quadrangles. This type of early professional experience can have profound implications for the careers of these students. Student knowledge gained includes the understanding of what it takes to systematically map bedrock exposures and structural zones, categorize the various rock types into lithologic map units, write out detailed descriptions of these map units, generate geologic cross sections and correlation diagrams, and putting all of these components together into a map that the geologic survey will subsequently publish. In today’s mineral industry, geologic maps are largely digital compilations of publicly available regional/district scale GIS data (downloaded and/or digitized from geological survey websites) merged/overlain with detailed industry geologic mapping of prospects and/or project areas. For the most part, the mineral industry quickly compiles digital data into geologic databases and is seemingly always searching for new ways to quickly capture data in the field digitally. The ease with which the mineral industry can generate digital geologic map products today can be good, bad, or ugly. The state of such geologic map outcomes by industry entities rests largely on the knowledge and experience of the company geologists. The US Geological Survey’s (USGS) Earth Mapping Resources Initiative (Earth MRI) program is a partnership of the USGS, the Association of American State Geologists (AASG) and other governmental, Tribal, and private-sector entities to update the nation’s surface and subsurface mapping to improve our knowledge of the geologic framework in the United States and to identify areas that may have the potential to contain undiscovered critical mineral resources. In November 2021, the US government passed the Infrastructure Investment and Jobs Act, one outcome of which is an investment of $320 million into Earth MRI to develop a better understanding of sustainable mineral production and mine waste options. An industry appeal to Earth MRI programs is to reinvigorate the education of future professional geologists by employing hundreds of geology student interns in upcoming geologic mapping projects. 65 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. The mineral development trapezoid. 66 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Fault zone architecture in mafic protoliths at the Lac des Iles mine, northwestern Ontario PETERZON, Jordan1, PHILLIPS, Noah1, HOLLINGS, Peter1, DJON, Lionnel2 1 2 Department of Geology, Lakehead University, 955 Oliver Road Thunder Bay, ON P7B 5E1, Canada Impala Canada, 69 Yonge Street, Suite 700 Toronto, ON M5E 1K3, Canada Faults are important geologic structures that host earthquakes and serve as permeable pathways through the upper crust. From an economic perspective, faults may transport and trap mineralized fluids. In turn, trapped mineralization may be offset or remobilized by later faulting. Fault zones are complex structures that produce an array of fault rock fabrics and architectures. Fault zone architecture typically consists of three components: 1) a fault core where most of the slip has been accommodated, 2) a damage zone bounding the fault core where fracture density increases with proximity to the fault core, and 3) an undeformed and less altered protolith. (Faulkner et al., 2010). Permeability is significantly enhanced in damage zones due to the high density of fractures and is diminished in fault cores due to the presence of clay-rich fault gouges. Faults may therefore act as conduits or barriers for fluid flow depending on the proportion of fault core to damage zone (i.e., the fault zone architecture; Caine et al., 1996). Fault zone architecture has been well studied in felsic to intermediate protoliths but studies on mafic protoliths are lacking. Here, we examine late faults within the mafic Lac des Iles complex to characterize fault zone architecture in mafic protoliths. The Lac des Iles complex is a series of mafic-ultramafic intrusive bodies occurring within the Marmion terrane of the Superior Province. The complex has been dated at 2689 ± 1.0 Ma and was emplaced into a ~3.01 – ~2.68 Ga granite-greenstone terrane (Djon et al., 2018). The Lac des Iles mine, owned and operated by Impala Canada, is a working Pt-Pd mine which is classified as a structurally controlled magmatic sulfide deposit. Extensive Ni-Cu-PGE mineralization has been offset by two late reverse faults in the high-grade zones (>4 g/t Pd): the Camp Lake fault and the Offset fault. A depletion in Pt-Pd mineralization is observed surrounding the late Camp Lake fault which extends ~180m into the hanging wall and ~145m into the footwall. Five drill holes that cross the late faults were logged and sampled in detail, with a fracture density counting program conducted systematically in the hanging wall and footwall. Fracture density increases as a power law function with proximity to the fault core and correlates with alteration. Tonalite has a higher fracture density and fracture density decay rate than gabbronorites near the fault. Fracture density and hematite/epidote alteration are more intense in the damage zone when faults cut through tonalite than when faults cut through gabbro. Fault cores in tonalite display a range of textures, from chlorite-rich gouges to fault breccias with calcitic matrix, while fault cores in gabbro only display chlorite-rich gouges. In this study, felsic protoliths have a higher fracture density than mafic protoliths indicating that fluid flow was more effective in felsic protoliths which may have contributed to depleted mineralization. This implies that host rock lithology strongly affects fault zone structure, including alteration assemblages, fracture densities, and permeabilities. 67 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Simplified regional map of the Lac des Iles intrusive complex (Djon et al., 2018). Figure 2. (A): Fracture density data from a single drill hole displaying an increase in fractures with proximity to faulting. (B): Underground exposure of the Camp Lake Fault at Lac des Iles. (C): Schematic of a typical fault zone architecture with corresponding cartoons of typical fracture density and permeability across the fault (Faulkner et al., 2010). References Caine, J.S., Evans, J.P., and Forster, C.B., 1996. Fault zone architecture and permeability structure. Geology, 24 (11): 1025-1028. Djon, M.L., Peck, D.C., Olivo, G.R., Miller, J.D., and Joy, B., 2008. Contrasting Style of Pd-rich Magmatic Sulfide Mineralization in the Lac des Iles Intrusive Complex, Ontario, Canada. Economic Geology, 113 (3): 741-767. Faulkner, D.R., Jackson, C.A.L., Lunn, R.J., Schlische, R.W., Shipton, Z.K., Wibberley, C.A.J., and Withjack, M.O., 2010. A review of recent developments concerning the structure, mechanics and fluid flow properties of fault zones. Journal of Structural Geology, 32 (11): 1557-1575. 68 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Mobile geologic mapping at the Wisconsin Geological and Natural History Survey REHWALD, Matthew1, AMES, Carsyn1, BREMMER, Sarah1, FITZPATRICK, William1, STEWART, Eric1, BATTEN, William1 and MAUEL, Stephen1 1 Wisconsin Geological and Natural History Survey, University of Wisconsin-Madison Division of Extension, 3817 Mineral Point Road, Madison, WI, 53705 The Wisconsin Geological and Natural History Survey (WGNHS) currently collects and analyzes data using a number of mobile applications for different purposes. Field data collection has become a tool for collection of new data and the verification of existing data. It has allowed the survey to create an automated pipeline to capture photos, notes, as well as record location information into one central location for a respective project. We had 4 objectives to implement while incorporating mobile applications. The application had to be 1) easy to use, 2) efficient, 3) easy to update, and 4) capable of displaying many datasets in the field. At the WGNHS we utilize mobile field applications for the collection of new data and the verification of existing map data. A mobile field application has the advantage of making many different data sets available to the user in the field within the flexible scale of a mobile GIS application. The incorporation of other mobile applications (FieldMove Clino) for data collection can increase efficiencies and are a vital to aid interpretations. Mobile field applications allow for field reconnaissance from almost anywhere. When considering a large project with a lot of data, increasing efficiency in field mapping techniques without compromising quality is important. Automating much of the data collection and data transfer eliminates the need for individuals to spend time cataloging digital pictures, copying field notes, and uploading field data. It’s a great advantage to be able to easily update or add additional map layers and data, and to see the data already collected. A visual display of data collection progress is useful in time management and project planning. The ease of which an application can be updated consumes time and affects project budget. Ease of use is also important, Accessibility and technical expertise should not be barriers to data collection. The ease of use of a mapping application has positive impacts the project participants, the project budget, and the project output. 69 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Diagram of the flow of geologic data from the source to and from the mobile application. Managing the data allows for customization of the functionality and the display of the data. 70 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Quaternary Geology of Wisconsin at a scale of 1:500,000 (in review) ROSE, Caroline1, RAWLING III, J. Elmo1, CARSON, Eric C.1, ATTIG, John W.1, MICKELSON, David M.1, MODE, William N.2, JOHNSON, Mark D.3, and SYVERSON, Kent M.4 1 Wisconsin Geological and Natural History Survey, 3817 Mineral Point Road, Madison, WI 53705 University of Wisconsin–Oshkosh Department of Geology, 645 Dempsey Trail, University of Wisconsin– Oshkosh, Oshkosh, WI 54901 3 Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden 4 University of Wisconsin–Eau Claire Dept. of Geology, 145 Phillips Hall, University of Wisconsin-Eau Claire, Eau Claire, WI 54702 2 In 2023 the Wisconsin Geological and Natural History Survey staff expect to publish a new statewide compilation map of Quaternary geology at a scale of 1:500,000. A preliminary version is presented here by the principal cartographer. Pre-existing statewide coverages of the surficial geology are limited to Chamberlin’s 1881 map of Quaternary formations and Hadley and Pelham’s 1976 map of glacial deposits at 1:500,000, which differentiates only six map units. No modern compilation of the surficial geology of the state at a scale of 1:500,000 or larger has been completed before. Figure 1. Statewide Quaternary geologic mapping in Wisconsin: Left: Chamberlin’s 1881 “Quaternary Formations of Wisconsin”. Center: Hadley and Pelham’s 1976 “Glacial Deposits of Wisconsin”. Right: Draft polygons of 1:500,000 scale surficial geologic map being compiled by WGNHS geologists. This effort began in 2019 due to a one-time funding opportunity from the US Geological Survey’s National Cooperative Geologic Mapping Program. Authors compiled previous mapping at 1:100,000 scale for 44 of Wisconsin’s 72 counties, along with partial mapping at the 1:100,000 scale and/or mapping at the 1:250,000 scale for 13 additional counties. Some areas had no prior mapping available at detailed scales. New map units have been developed for the 1:500,000 scale and are divided into glacial and nonglacial sediment that is characterized by lithology and subdivided by geomorphology. Glacial deposits are mapped at the formation level following the WGNHS Lexicon of Pleistocene Stratigraphic Units. We use color hue to differentiate among the various glacial formations by source areas with green groupings derived from the Superior basin, blue groupings from the 71 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Michigan basin. We assign the darkest colors to the strings of moraines and hummocky till marking the extent of glacial lobes of the most recent Wisconsin Glaciation. Nonglacial Quaternary units are generally shown in warm colors, including modern alluvium, colluvium, lake deposits, and meltwater stream deposits, with small pockets of terraces which are highlighted along major river valleys. The Driftless Area in southwestern Wisconsin shows the dendritic patterns of eroding colluvium along branching alluvial tributaries with windblown silt on the uplands. Some large deposits of organic sediment and areas of exposed or thinly covered bedrock are included at this scale. This map layout is being produced entirely in ArcGIS Pro, which is a relatively new layout process for our office. We are organizing the GIS data according to the USGS standard Geologic Map Schema (“GeMS”), and we make use of this data structure to draw the unit description text in the Explanation of Map Units (legend) directly from a table in the geodatabase using a dynamic text element. This saves us from the extra work of synchronizing the layout text with the database text. Although ArcGIS Pro does not natively offer an easy solution for geologic map legends, we have been able to find a series of work-arounds to achieve the desired legend layout. References Chamberlin, T.C., 1881. General map of the Quaternary formations of Wisconsin, plate 2 of Atlas of the Geological Survey of Wisconsin: [Madison, Wisc.], Wisconsin Geological Survey, scale approximately 1:960,000. Hadley, D.W., and Pelham, J.H., 1976. Glacial deposits of Wisconsin—Sand and gravel resource potential: Wisconsin Geological and Natural History Survey Map M061: 19 p., 1 pl., scale 1:500,000, https://wgnhs.wisc.edu/catalog/publication/000385 [Previously Map 10.]. Acomb, L., Attig, J.W., Baker, R.W., Brownell, J., Clayton, Lee, Fricke, C., Frolking, T.A., Frye, J.C., Hemstad, C., Jacobs, P.M., Johnson, M.D., Knox, J.C., Leigh, D.S., Mason, J.A., McCartney, M.C., Mickelson, D.M., Mode, W.N., Muldoon, M.A., Need, E.A., Schneider, A.F., Simpkins, W.W., Socha, B.J., Syverson, K.M., Willman, H.B., 2011. Lexicon of Pleistocene Stratigraphic Units of Wisconsin: Wisconsin Geological and Natural History Survey Technical Report 001: 180. 72 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Tips from a GIS Specialist: Moving maps to GeMS, and a utility for georeferencing quadrangles ROSE, Caroline1 1 Wisconsin Geological and Natural History Survey, 3817 Mineral Point Road, Madison, WI 53705 USA The USGS has recently been requiring that geologic mapping deliverables use their new standard database format, called the Geologic Map Schema, or “GeMS.” The Wisconsin Geological and Natural History Survey (WGNHS) began converting geologic maps into the GeMS format four years ago. I will offer a brief overview of GeMS and will use the GIS data for the Geology of LaCrosse County map (available for download on our website) to demonstrate how GeMS captures the components of a geologic map in geodatabase format. We have created several documents to facilitate the process of migrating maps into GeMS, and we have made them available in this Github repository: https://github.com/wgnhs/gems. My advice to anyone beginning this process is to first consult our “Workflow Overview” document for a high-level summary of the steps. When completing the GeMS-specified attributes, the “Quick-Reference Sheets” are a convenient arrangement of the GeMS documentation, with each layer or table printed on a separate reference sheet, to put focus on one layer or table at a time. To help verify that a GeMS database is complete, the “GeMS Fields Checklist” is designed to help in confirming completion of GeMS attributes. Two of our documents address the process of authoring metadata for a GeMS geodatabase. The document titled “Metadata For GeMS Maps - Step by Step in ArcCatalog” is a guide to starting FGDC metadata in ArcCatalog before using the USGS-provided metadata script. The “Metadata Summary for GeMS Fields” is a reference to show where GeMS attributes appear in the FGDC metadata, as produced by the metadata script. All of these documents are housed on our github page, along with other resources such as python scripts and slides from various presentations. We are making it a priority to share these with other GeMS users; we hope these resources are useful to other organizations working through the process of converting maps into GeMS. I will also briefly summarize how we have involved the GeMS format in our map layouts in ArcGIS Pro by drawing from the Description of Map Units table to automatically lay out the legend using Dynamic Text elements. In the second half of this talk, I will give an overview of a semi-automated utility for georeferencing maps, especially USGS quadrangles. The software is called QuadG+ and was developed by USGS and University of Wisconsin collaborators to build the Historical Topographic Map Collection. It is available for free download at https://geography.wisc.edu/quad-g/ and has proven useful to Wisconsin survey staff for georeferencing maps with field notes. 73 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. The free software QuadG+ automatically detects the corners and other control marks in a scan of a USGS quadrangle References Burt, James E., Jeremy White, Gregory Allord, Kenneth Then, A-Xing Zhu, 2022. Quad-G+: Automated Georeferencing of Scanned Map Images User Manual Version 2.13 December 2022. University of Wisconsin – Madison. Accessed March 27, 2023. https://uwmadison.app.box.com/s/tkccw1j5u3ensn2e10hrl1eiek78z9r6/file/1125666147300. 74 �Proceedings of the 69th ILSG Annual Meeting – Part 1 New work developing Keweenaw geoheritage awareness ROSE, William1 1 Department of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 U.S.A. Telling Keweenaw Geostories in ~ten minutes. Old stories of Keweenaw geohistory have been made into web-based illustrated summaries meant to fill awareness of geoheritage from literature sources. About 8-15 minutes long with ~20 illustrations, these stories tell about the Ontonagon Boulder, Douglass Houghton, Louis Agassiz, Jane Schoolcraft and Hiawatha, Pasties and Keweenaw Miners, Big Annie and the 1913 Strike, Discovery of the Keweenaw Fault, the Green Rock at Copper Harbor, Ben Franklin and Lake Superior, and the Discovery of the C&H Conglomerate. The stories may be viewed online (https:// vimeo.com/showcase/9801619). They show how local history is guided by geology. They are intended to supplement local and statewide awareness and pride. Bringing the Boulder Home to the UP. The Ontonagon Boulder was a legendary float of native copper 75 �Proceedings of the 69th ILSG Annual Meeting – Part 1 which was on the west branch of the Ontonagon River until 1847 (https://vimeo.com/showcase/9801619/ video/785968264). The word of mouth of this unusual precious rock led to widespread interest, but it was difficult to move. Dispute over the ownership of the Boulder was spirited, and eventually it ended up in Washington DC at the Smithsonian Mineral Science Museum. The Boulder is considered a sacred object by Ojibway (Erik Redix, 2017, American Indian Quarterly, 41 (3)). Repatriation of the boulder to the UP was applied for, but rejected by the Smithsonian in 2000. UP residents and tourists have no access to this iconic legend. Currently (for decades) the boulder resides out of public view. We propose a loan of the boulder to allow it to visit museums such as Cranbrook, Univ of Michigan and the AE Seaman Mineralogical Museum, partner of the Keweenaw National Historic Park Building a Statue of a feminist labor leader. Anna Klobuchar Clemenc was a feminist labor leader in Calumet during the miners’ strike of 1913 (https://vimeo.com/showcase/9801619/video/748833299). She had fame for her leadership of labor parades when she wrapped herself in the American Flag to inhibit the violent confrontations. Tall and homely, “Big Annie” used her personnage advantageously and allied with the Western Federation of Miners. She worked with Mother Jones and with the women’s vote efforts in Washington. She was the first member of the Michigan Women's Hall of Fame. The Michigan legislature has officially named June 17 as “Big Annie Day”. A bronze life-sized statue of her is planned for permanent display in Red Jacket, outside of the Calumet Opera House and one block away from the Italian Hall. For more info: https://www.facebook.com/profile.php?id=100090193837168 76 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Outcrop Scale Mapping Utilizing High-Accuracy GNSS with MnDOT’s Virtual Reference Station (VRS) Network: Minnesota Examples SCHULZ, Roger1 1 Big Rock Exploration Geologic mapping has long been utilized to visualize the underlying geology of a region. An important tool used in geologic mapping are those that resolve the mapper’s locations at a given time. The tools used to locate a mapper have advanced greatly since the time of pace and compass, chains, and grids. With that advancement comes ever more accurate location data. One of the most common modern mapping tools utilizes satellite networks to send a signal from which location data is calculated on a consumer grade handheld GPS unit. While handheld GPS’s are useful in mapping moderate to small scale (e.g., 1:5000 or 1:24,000), the accuracy limitations of these units are not capable of resolving outcrop-size maps (e.g., <1:250 scale). Given the limited outcrop in places like the Lake Superior region, it is necessary to extract all possible data from a given outcrop, lending greater importance to small-scale maps. Attaining a level of location accuracy needed for such outcrop scale mapping requires additional real-time corrections of satellite data. The Global Navigation Satellite System (GNSS) encompasses three major satellite networks operated by the USA (GPS), Russia (GLONASS), and the EU (Galileo). When utilized within the GNSS framework, it is possible to have reliable satellite coverage anywhere in the world, a requirement for accurate location data. GNSS functions via one-way communication of radio waves from the satellites to a receiver that calculates distance from the satellite to the receiver. Distance calculations based on the speed of the signal (c) and the time differential (Δt) between the signal being sent then picked up by the receiver (D = c • Δt). To triangulate the position of the observer, this calculation must be solved by multiple satellites. This results in positional data that is generally accurate to 10m in the horizontal, at best. The reason for the inaccuracy is that the atmosphere interferes with the speed of the signal resulting in a delay. It is possible to achieve more accurate data by correcting for this differential delay using established ground-based networks. Differential correction using Virtual Reference Station (VRS) utilizes base stations at control monuments that continually collect positional data generating an average position that can be used to determine the degree of atmospheric delay. When used in a network of base stations, the average atmospheric delay for an area can be determined. The regional delay, or differential, can be communicated to a handheld unit over an internet connection, thereby eliminating the effect of atmospheric delay. Positions can then be determined to centimeter-scale accuracy, a requirement of mapping outcrop scale features. MNDOT has implemented a statewide Virtual Reference Station (VRS) network with over 140 base stations over control monuments whose purpose is to correct for the atmospheric delay and generate high-accuracy GNSS datasets.2 This network is free to use for anyone. Figure 1 below is a case study from South Pass, Wyoming where a trench was mapped at 1:250 using a Trimble Geo 7x. The trench this study area contained auriferous quartz veins and barren quartz veins anastomose along a pair of sheared faults separated by several meters and are connected ladder veinlets. Without the decimeter-scale accuracy of the corrected positional data, it would not have been possible to accurately locate the geology, geochemical samples, or structural data within the trench and the adjacent outcrops. Such an approach could be extremely useful in visualizing complex intrusive outcrops in the Duluth Complex, tracing of the contacts of lava flows and interflow sediments along the shore of Lake Superior, and veins and stockworks within Archean rocks. 77 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Trench Mapping and Sampling for Relevant Gold Corp at the Golden Buffalo Project - South Pass, Wyoming. by Big Rock Exploration LLC References GNSS Timing and Atmospheric Interferences: How GNSS Is Solving These Problems. Global GPS Systems, 24 Jan. 2023, https://globalgpssystems.com/gnss/gnss-timing-and-atmospheric-interferences-how-gnss-issolving-these-problems/. Land Management. MnCORS Network - Land Management - MnDOT, https://www.dot.state.mn.us/surveying/cors/index.html. Understanding RTK VRS Networks. Global GPS Systems, 24 Jan. 2023, https://globalgpssystems.com/gnss/understanding-rtk-vrs-networks/. 78 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Geology and geochemistry of the basal North Shore Volcanic Group and Midcontinent Rift Intrusive Supersuite, Cook County, MN, USA SEVERSON, Allison R.1, NOWARIAK, Eric S.1, LARSON, Phillip C.2 1 Minnesota Geological Survey, Department of Earth and Environmental Sciences, University of Minnesota-Twin Cities, MN, USA 2 Vesterheim Geoscience PLC, Duluth, MN, USA Northeastern Minnesota preserves complex relationships between Mesoproterozoic volcanic flows and comagmatic gabbroic to granophyric intrusive rocks associated with the ca. 1.1 Ga Midcontinent Rift System (MRS), as well as Paleoproterozoic metasedimentary rocks. Over the last two years, bedrock mapping of nine 1:24K quadrangles in northeastern-most Minnesota (Fig. 1) has elucidated some of these relationships between the Rove Formation, Logan sills, Puckwunge sandstone, reversely polarized North Shore Volcanic Group (NSVG), and gabbroic and granophyric rocks of the Midcontinent Rift Intrusive Supersuite. Results described herein are based on field and thin section observations, and associated geochemistry, which will be compiled and published as part of the Minnesota Geological Survey’s County Geologic Atlas Series. Volcanic rocks lie conformably on top of the Puckwunge sandstone in the eastern map area (Fig. 1). In the western part of the map area, the Crocodile Lake Gabbro (CLG) is in contact with the Paleoproterozoic Rove Formation to the north, with the Rove being highly deformed, metamorphosed, and partially melted proximal to the contact. South of the CLG, is the coeval Cucumber Lake Granophyre (CLGp), which is in contact with the Grand Portage Lavas (GPL), Esther Lake Lavas (EL), and Hovland Lavas (HL) of the NSVG to the south. The NSVG youngs from north to south, and transitions from mafic to more felsic from north to south which is most evident in the transition from the GPL to the overlying EL (Fig. 1). Geochemically, this sequence evolves along a strong tholeiitic trend (Fig. 2). Lithologic and geochemical patterns suggest the >1108 Ma GPL, EL, and HL were likely sourced from a long-lived, evolving magma. The basal GPL amygdaloidal basalt preserves 5 - 75 cm long pillows with somewhat enigmatic siliceous, carbonate, and glassy selvages that also preserve hyaloclastic and perlitic textures. These flows are geochemically primitive and contain abundant altered olivine, pyroxene, and oxide phenocrysts. The pillowed basal unit grades into thick, massive to ophitic basaltic and basaltic andesite flows of the EL. The transition from the GPL is also marked by a change in trace element geochemistry from an enriched mantle to a more depleted mantle signature. The base of the HL consists of a package of strongly glomeroporphyritic, amygdaloidal andesites and basaltic andesites transitioning to porphyritic rhyolite and icelandite. Porphyritic basaltic to andesitic lavas in the westernmost map area also preserve pillow structures, but these flows vary in thickness and extent, suggesting aqueous subbasins within the HL volcanic basin. Intercalated throughout the HL are abundant dikes and sills of ultraphyric diabase containing 15-60% of >5 mm plagioclase phenocrysts within a basaltic, locally ophitic very fine-grained groundmass. These intrusives are interpreted to be hypabyssal and locally cut across volcanic stratigraphy. Though these dikes and sills are endemic to the area, temporal relationships between these intrusives, the surrounding volcanics, and the Brule-Hovland Gabbro are unknown. The ca. 1107 Ma CLG and the CLGp comprise some of the earliest known rocks within the intrusive Duluth Complex. Basal gabbroic cumulates of the CLG grade into dioritic-monzonitic rocks of the Crocodile Lake “Mixed Zone”, below the contact with the overlying CLGp. This Mixed Zone is typified by complex dikes and plagioclase cumulate rocks, rich in micrographic interstitial felsic mesostasis. Abundant quench textures and pegmatitic zones, as well as distinct geochemical patterns 79 �Proceedings of the 69th ILSG Annual Meeting – Part 1 suggest the Mixed Zone is a “cap” to the CLG rather than a gradual transition to the CLGp. REE patterns and Eu anomalies within these coeval intrusives suggest liquid immiscibility between mafic and felsic components of the source magma may have played a significant role in their genesis (Fig 3.). Other intrusive gabbroic rocks include the texturally varied Brule-Hovland Gabbro, which cross-cuts the HL. Figure 1. Regional geologic map of northeastern Cook County, MN. Ongoing partially USGS-funded STATEMAP projects outlined with bold lines. Generalized geology is from MGS miscellaneous map series M-119. Figure 2. AFM diagram of volcanic rocks. Figure 3. Chondrite-normalized REE diagram of Crocodile Lake and Cucumber Lake intrusives, based on Sun and McDonough, 1989. 80 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Exploring the application of full tensor magnetic gradiometry to better define conduit type NiCu-PGE targets SMITH, Jennifer1, TSCHIRHART, Victoria1, TUCK, Loughlin2, ENKIN, Randy1, and ROYGUAY, David3 1 Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0E8 Defence Research and Development Canada, Ottawa 3 SBQuantum,Sherbrooke, QC, J1H 1Z1 2 Magmatic Ni-Cu-PGE sulfide deposits are often associated with small conduit- or chonolithtype intrusions. These deposit types are notoriously challenging exploration targets owing to: 1) their small size, 2) lack of alteration halo or distal footprint, 3) complex and variable morphology, and 4) unpredictable depositional sites of sulfides (Barnes 2023). Furthermore, mafic rocks commonly retain significant remanent magnetization which, if not detected, can result in inaccurate modelling and targeting of these deposits. With a significant increase in the global production of Ni forecasted for the transition to a low-CO2 future, these deposit types will likely become an increasingly important source of Ni, both in Canada and globally. With fewer new discoveries being made, despite increased exploration expenditure, new methods and knowledge are needed to facilitate successful exploration at the regional and deposit scales and to ultimately secure a stable Ni supply. Historically, exploration has traditionally relied on geophysics (gravity, magnetics, electromagnetics), to identify potential mafic and/or ultramafic host intrusions, with airborne magnetic surveying dominating due to its low cost, and ability to survey vast areas rapidly and systemically. Although there is incredible value in Total Magnetic Intensity (TMI) data there are numerous limitations to this approach (e.g. non-uniqueness, scalar measurements, can’t distinguish remanence from induced field). The full tensor magnetic gradiometry (FTMG) technique, which measures the full magnetic gradient tensor at each measurement point, overcomes many of the limitations of TMI data. Advantages of FTMG include: (a) superior resolution of near-field sources, (b) enhanced detectability at low-magnetic latitudes, (c) automatic removal of the regional field and diurnal variations, and (d) additional target information from a single flight line. FTMG can provide a more complete picture of the subsurface magnetic properties and improved discrimination between magnetic sources. This leads to improved imaging of complex structures, more accurate models of the subsurface, and improved understanding of geological processes. While quantum FTMG is in use by industry, practicalities relating to the system hamper its widespread deployment. Currently, existing quantum FTMG relies on SQUID technology for large scale airborne surveying. The application of SQUID technology has shown great benefits due to the enhanced sensitivity and fidelity of the system. However, these systems typically weigh ~270 kg and require extremely low sensor temperatures, making them impractical for ground and uncrewed aerial vehicle (UAV) surveying. These limitations have warranted the development of a complimentary ground and UAV quantum FTMG system such as the diamond-based quantum magnetometer in development by SBQuantum. This rugged and compact system leverages quantum properties of nitrogen vacancy (NV) centres in a diamond to provide highly accurate, quantum-based FTMG measurements. The Geological Survey of Canada (GSC) is in the early stages of establishing a new collaborative partnership with Defence Research and Development Canada (DRDC), SBQuantum, and numerous other industry and academic partners. The aim of this partnership and wider project is to derisk quantum magnetic gradiometer use across Canada with the purpose of facilitating widespread adoption by the Canadian exploration industry, academia and the military. This will be achieved 81 �Proceedings of the 69th ILSG Annual Meeting – Part 1 through the field testing and validation of the ruggedized quantum FTMG system developed by SBQuantum. As part of this project, SBQ’s quantum magnetic gradiometer will be deployed on several Canadian critical mineral systems, allowing comparison with traditional airborne and/or ground total magnetic field systems and non-quantum FTMG systems. As part of this, a detailed study will be undertaken on the Ni-Cu-PGE bearing Escape Lake intrusion in northern Ontario, which presents as a complicated magnetic signal that is strongly affected by remanent magnetization and associated with the 1.1. Ga Midcontinent Rift. With conventional total field geophysical methods unable to address the challenging features which are often characteristic of small, conduit-type magmatic sulfide deposits, this case study will explore the use and application of quantum FTMG in the context of improving targeting of conduit type Ni-Cu-PGE deposits. This study will be the first to generate publicly accessible quantum FTMG data over critical mineral deposits in Canada and will act to improve exploration capacity by validating tools useful for critical metal deposits whose complex geophysical expressions are not easily resolved by traditional geophysical techniques. The increased accuracy of these quantum technologies, which map the magnetic field at an enhanced scale, provide the ability to resolve the complexity of these deposits. Providing enhanced tools to facilitate exploration and delineate deposits better will aid with the identification of new Canadian deposits of critical metals needed for the lower carbon and digitized economy supply chain. This will aid Canada’s Critical Minerals Strategy set forth in the 2022 Federal Budget. References Barnes, S.J., 2023. Lithogeochemistry in exploration for intrusion-hosted magmatic Ni–Cu–Co deposits. Geochemistry: Exploration, Environment, Analysis, 23(1): geochem2022-025. 82 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Record of an Ancient Meteorite Impact Buried Beneath the Twin Cities, MN STEENBERG, Julia R. 1, and RUNKEL, Anthony C. 1 1 Minnesota Geological Survey, 2606 W. Territorial Rd., St. Paul, MN 55114 USA An impact crater is proposed in the southeast part of the Twin Cities metropolitan area, 11 miles (18 km) south of St. Paul within an area with significant residential and industrial development. The crater lies within a predictable package of Paleozoic sedimentary rocks in the Twin Cities structural basin where near its center includes 14 formations with a total thickness of about 1,200 feet (365 meters) (Mossler, 2008; Mossler, 2013). Paleozoic formations are characterized by widespread layers of sandstone, shale, and carbonate deposited in shallow seas during the Cambrian and Ordovician Periods (500 to 450 Ma). They are underlain by Mesoproterozoic (1,100 Ma) sedimentary and volcanic rocks of the Keweenawan Supergroup associated with the Midcontinent Rift. Paleozoic rocks in this area have limited exposure along the Mississippi and Minnesota River bluffs, roadcuts, and rock quarries, but elsewhere are buried beneath a variable thickness of Quaternary glacial sediments. Without extensive exposures, a variety of subsurface datasets are used for bedrock mapping including core, drill cuttings, geophysical logs, passive seismic stations, and driller’s descriptions from water well records. While mapping the bedrock geology of Dakota County, an area of discordance with the surrounding Paleozoic stratigraphy was observed in geologic cuttings samples, and corroborated with additional cuttings, geophysical logs and water wells driller’s records. Drill samples reveal as much as 575 ft (175 m) of anomalous sandstone, siltstone and shale with some intervals containing abundant cloudy and fractured quartz sand grains. The samples are from an area entirely buried by several hundred feet of glacial deposits within a deep buried channel carved into the surrounding bedrock layers adjacent to the Mississippi River near the city of Inver Grove Heights. Beneath the anomalous sequence of strata and in additional samples near the site, local Cambrian and Mesoproterozoic stratigraphic layers are recognized but are out of the usual stratigraphic order and in places entirely overturned. Microscopic investigation has resulted in the detection of shocked metamorphic features including planar deformation features (PDFs) in the fractured quartz grains, confirming the impact origin of this structure (Fig. 1). As such, this area is referred to as the Pine Bend Impact Structure (PBIS) (Steenberg, in prep). Based on the available geologic data near the site and current models of crater formation from similarly sized structures in layered sedimentary target rocks we interpret this feature to be a complex crater, approximately 4 km wide with an apparent central uplift and possible terraced rims (Grieve, 1991). The total disturbed area may be as large as 9 square miles (23 square kilometers). Based on published crater- to- meteor size ratios, the size of the meteor is estimated to be several hundred meters in diameter (Grieve and Pilkington, 1996). Due to its location, within a buried bedrock valley, the upper sequence of this structure has been removed by erosion, making it difficult to precisely date the impact. It may be as old as Late Cambrian (~490 Ma), having occurred during or after deposition of the Jordan Sandstone based on the age of the overturned strata and the apparent lack of carbonate from the overlying Prairie du Chien Group in the samples. We have also collected a pebble with PDFs from strata approximating the Jordan-Prairie du Chien contact in an outcrop about 10 kilometers from the crater. If this pebble is ejecta from the PBIS, it also supports a latest Cambrian or very Early Ordovician age of impact. This would make the PBIS older than known craters in surrounding states which are Ordovician and younger (French et al., 2004; French et al., 2018). The dynamic nature of our planet has left us with a small sample size of terrestrial impact structures, nearly 200 confirmed impact structures are currently recognized on Earth (Gottwald et al., 2020). Although Minnesota has known impact debris from the Sudbury Impact Structure, this would 83 �Proceedings of the 69th ILSG Annual Meeting – Part 1 be Minnesota’s first documented crater, giving us a rare opportunity to better understand the important geological and biological effects of meteorite impact events on Earth. Figure 1. Photomicrographs of mounted quartz sandstone rock chips from a cuttings sample, sample depth is 525 feet. A- Two sets of planar features and feather features. B- One set of decorated planar deformation features. Photos by L. Ferriere, Natural History Museum, Vienna, Austria. References French, B.M., Cordua, W., and Plescia, J.B., 2004. The Rock Elm meteorite impact structure, Wisconsin: Geology and shock-metamorphic effects in quartz. GSA Bulletin, 116: 200–218. French, B.M., McKay, R.M., Liu, H.P., Briggs, D.E.G., and Witzke, B.J., 2018. The Decorah structure, northeastern Iowa: Geology and evidence for formation by meteorite impact. GSA Bulletin, 130: 2062– 2086. Gottwald, M., Kenkmann, T., and Reimold, W.U., 2020. Terrestrial impact structure. In: TheTan-DEM-X Atlas, Part 1 and 2, Friedrich Pfeil, Munich, Germany. Verlag Dr. Grieve, R.A.F., 1991. Terrestrial impact: the record in the rocks. Meteoritics, 26: 175–194. Grieve, R.A.F., and Pilkington, M., 1996. The signature of terrestrial impacts. AGSO Journal of Australian Geology and Geophysics, 16: 399-420. Mossler, J.H., 2008. Paleozoic stratigraphic nomenclature for Minnesota. Minnesota Geological Survey Report of Investigations RI-65: 76, 1 pl. Mossler, J.H., 2013. Bedrock geology of the Twin Cities ten-county metropolitan area, Minnesota. Minnesota Geological Survey Miscellaneous Map M-194: scale 1:125,000. Steenberg, J.R., in prep. Bedrock geology, pl. 2 of Steenberg, J.R., project manager, Geologic atlas of Dakota County, Minnesota. Minnesota Geological Survey County Atlas C-57: 6 pls., scale 1:100,000. 84 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Magma Recharge and the distribution of Copper and Nickel in the Keweenaw Large Igneous Province STEINER, Alex1, PETERSON, Dean1, SWEET, Gabriel1 1 Big Rock Exploration, 2505 W. Superior Street, Duluth, MN 55806. The Keweenaw large igneous province (LIP) was formed over a protracted period of magmatism that emplaced Cu-Ni-PGE bearing mafic to ultramafic intrusions along the arcuate MidContinent Rift system, thus creating one of the largest critical mineral resources in North America. The magmatic activity associated with the Keweenaw LIP has been divided into a series of tectonomagmatic stages extending from at least 1115 Ma to 1080 Ma. Of the six stages of formation, significant orthomagmatic sulfide deposits were formed during Stage 1 (plume impact stage; 11151110 Ma), Stage 2 (early stage; 1110-1105 Ma), and the Stage 4 (the main stage; 1101-1094 Ma). Stage 1 and 2 intrusions in the Minnesota and Michigan are Ni-rich while those of stage 4 in the Duluth Complex are considerably more copper-rich. Here we discuss a potential mechanism of copper enrichment via magma recharge-evacuation-fractional crystallization (REAFC) where the parameters of differentiation are based upon a conceptual model for the formation of continental LIPs. It has been recognized that continental LIPs form in a series of phases that reflect the conditions of magma generation and differentiation prior to the eruption and eventual formation of continental flood basalts (Jerram and Widdowson, 2005). Early phases of LIP formation are dominated by more primitive lavas, that pass through a magma plumbing system that is immature and inefficient at differentiating magmas (Steiner et al., 2021). However, the magmatic plumbing system of the most voluminous eruptive phase is mature and capable of differentiating magmas to a considerable degree. The key difference between these two periods is the amount of magma recharge, which has a profound impact on the geochemical composition of the resultant magmas where compatible elements become buffered and incompatible elements become enriched (Lee, Lee and Wu, 2014). The relative Cu-enrichment of mineralized Stage 4 intrusions compared to earlier Ni-rich Stage 1 and 2 intrusions may be explained by several mechanisms. Mechanisms such as sulfide upgrading and high-R factors have been recognized as important contributors to Cu-rich mineralization (Peterson and Boerst, 2013). However, recent chemo-stratigraphic examinations of Keweenaw LIP lavas from the Keweenaw Peninsula have demonstrated that REAFC processes are controlling erupted lava compositions during the eruption of Stage 4 lavas (Davis et al., 2021). To test the effect of REAFC on the proportions of Ni and Cu that may be available to form an orthomagmatic sulfide deposit, REAFC geochemical modelling utilizing the equations of Lee et al. (2014) were performed on a generalized basaltic composition (MgO = 10%, Ni = 250 ppm, Cu = 116 ppm (Prinz, 1967)). Figure 1 demonstrates the liquid line of descent for Cu, Ni, and MgO during REAFC differentiation and pure fractional crystallization. During pure fractional crystallization, MgO and Ni behave compatibly, gradually decreasing in concentration with continued differentiation while Cu gradually increases. However, during REAFC differentiation, both Ni and MgO become buffered while Cu becomes decoupled, increasing in concentration while Ni and MgO remain the constant. The consequence of this decoupling is that Cu can become considerably enriched relative to Ni, thereby producing a magma that contains greater than anticipated Cu concentrations compared to pure fractional crystallization. When this Cu-enriched magma reaches sulfur saturation, the subsequent sulfide magma would have a greater abundance of Cu to scavenge, resulting in the Cu-rich sulfide deposits observed in in the Duluth Complex. 85 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. REAFC calculations (Lee, Lee and Wu, 2014) for a generic basalt. Model parameters are recharge/evacuation = 0.43, assimilation = 0.07, fractional crystallization = 0.5. Crystallizing phases were olivine (25%), plagioclase (65%), and clinopyroxene (15%). References Davis, W.R. et al., 2021. Geochemical, petrographic, and stratigraphic analyses of the Portage Lake Volcanics of the Keweenawan CFBP: implications for the evolution of main stage volcanism in continental flood basalt provinces, Geological Society, London, Special Publications: SP518-2020–221. doi:10.1144/SP518-2020-221. Jerram, D.A. and Widdowson, M., 2005. The anatomy of Continental Flood Basalt Provinces: geological constraints on the processes and products of flood volcanism, Lithos, 79(3): 385–405. doi:https://doi.org/10.1016/j.lithos.2004.09.009. Lee, C.-T.A., Lee, T.C. and Wu, C.-T., 2014. Modeling the compositional evolution of recharging, evacuating, and fractionating (REFC) magma chambers: Implications for differentiation of arc magmas, Geochimica et Cosmochimica Acta, 143: 8–22. doi:10.1016/j.gca.2013.08.009. Peterson, D. and Boerst, K., 2013. Twin Metals Minnesota’s Maturi Deposit, in Cu-Ni-PGE Deposits of the Duluth Complex, Geology and Development: Precambrian Research Center, Workshop on the Copper, Nickel, Platinum Group Element Deposits of the Lake Superior RegionOctober 6-13, 2013, Field Trip Guidebook: 45–57. Prinz, M., 1967. Geochemistry of basaltic rocks: trace elements. In’, Basalts, 1: 271–333. Steiner, R.A. et al., 2021. Initial Cenozoic Magmatic Activity in East Africa: New Geochemical Constraints on Magma Distribution within the Eocene Continental Flood Basalt Province, Geological Society, London, Special Publications: SP518-2020–262. doi:10.1144/SP518-2020-262. 86 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Relay zones in weakly folded and faulted Paleozoic strata and their role localizing Mississippi Valley-type mineralization, southwest Wisconsin, USA STEWART, Eric1, FITZPATRICK, William1, and AMES, Carsyn1 1 Wisconsin Geological and Natural History Survey, 3817 Mineral Point Road, Madison, WI, 53705 Folds and faults have long been known to play a role in localizing Mississippi Valley-type zinclead mineralization in the historic Upper Mississippi Valley base metal district (UMVD) of southwestern Wisconsin. However, a simple correlation between mineralization and map-scale structures is overly simplistic since it does not explain why mineralization often occurs only along isolated portions of folds and faults. New 1:24,000 scale geologic mapping as part of the United States Geological Survey Earth Mapping Resources Initiative (EarthMRI) in the Stitzer region of the northern UMVD was initiated to improve understanding of the relationship between folds, faults, and mineralization. The Mineral Point anticline is the dominant structure in the Stitzer area (Figure 1). It is an asymmetric, northwest-trending gentle fold with a maximum amplitude of around 180 feet. The fold deforms platform Cambrian and Ordovician siliciclastic and carbonate strata, and contains several doubly plunging segments. Structural highs along the fold (Figure 1) correspond to aeromagnetic anomalies (Daniels and Snyder, 2002). Deformation bands in sandstone are common along the more steeply dipping northeast limb of the fold. The asymmetry of the fold and the correspondence of structural highs to aeromagnetic anomalies suggest the Mineral Point anticline is a forced fold, forming from thrust reactivation of a buried Precambrian fault. At depth near the Precambrian basement, the segments of the Mineral Point anticline probably transition into fault segments. Simple 2D kinematic modeling suggests contraction is highest near the base of the overlying folded section. If deformation bands accommodate some of the contraction in the basal siliciclastic sequence, then significant numbers of deformation bands are probably present low in the Paleozoic section. Mineralization and historic mining are heavily concentrated where two segments of the Mineral Point anticline overlap, and a third smaller anticline terminates (Figure 1). The area between the overlapping segments of the Mineral Point anticline is interpreted to represent the area above a relay zone between thrust segments. As mineralizing brines approached the Mineral Point anticline from the south, flow was probably altered due to the abundance of impermeable deformation bands. Flow conduits developed in the relay zone between fault-fold segments, focusing the brines upward and concentrating mineralization. References Carlson, J., 1961. Geology of the Montfort and Linden Quadrangles, Wisconsin, in Geology of parts of the Upper Mississippi Valley zinc-lead district. U.S. Geological Survey Bulletin 1123–B: 95– 138, 2 pls. Daniels, D. and Snyder, S., 2002. Wisconsin aeromagnetic and gravity maps and data; a web site for distribution of data. U.S. Geological Survey Open-File Report 2002-493. Taylor, A., 1964. Geology of the Rewey and Mifflin quadrangles, Wisconsin, in Geology of parts of the Upper Mississippi Valley zinc-lead district. U.S. Geological Survey Bulletin 1123–F: 279–360, 2 pls. West, W., 1971. Geologic map of the Ellenboro quadrangle, Grant County, Wisconsin. U.S. Geological Survey Geologic Quadrangle Series 959: 1 pl. 87 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Figure 1. Simplified structure contour map of the base of the Ordovician Platteville Formation. Mines are concentrated in the SE portion of the map near the junction of three anticline-syncline pairs. Additional data sources include the Mineral Development Atlas, Carlson (1961), West (1971), and Taylor (1964). 88 �Proceedings of the 69th ILSG Annual Meeting – Part 1 Deciphering the metamorphic and deformational history of the Hardwood Gneiss, Felch District, Michigan: Anomalously high-pressure rocks in the heart of the Penokean orogen TAYLOR, Madeline1 and BJØRNERUD, Marcia1 1 Geosciences Department, Lawrence University, Appleton Wisconsin 54911 The Neoarchean Hardwood Gneiss is a mafic granulite with minor metapelites, exposed over an area of about 6 km2 between the towns of Foster City and Hardwood, MI, 8 km southeast of the eastern end of the Paleoproterozoic “Felch Trough” (James, 1961). The area lies at the heart of the ca. 1.85 Ga Penokean orogen and within the superimposed Yavapai-age (1.75 Ga) ‘gneiss dome corridor’ (Drenth et al., 2021). In contrast to the primarily felsic gneisses of the region, which contain inherited zircons with ages of 3.8-3.5 Ga, the Hardwood Gneiss is mostly mafic and yields no zircons older than 2.7 Ga (Ayuso et al., 2018). Zircons from the Hardwood also record a period of growth between 2.2 and 1.9 Ga, which does not correspond to any known thermal events in the region (Cannon et al., 2018). Most notably, the Hardwood experienced much higher-pressure metamorphism than any other rocks in the region. Using a variety of geo- thermometers and -barometers, Peterson & Geiger (1990) concluded that the mafic rocks underwent two distinct metamorphic events, the first, ‘M1’, at 8.2-11.6 kbar and ca. 770°C, and a another, ‘M2’, at 6-10 kbar and 610-740°C, while the pelites experienced only the second. Maximum pressure estimates for the nearby Peavy metamorphic node, in contrast, are < 5 kbar (Attoh and Klasner, 1989). It is difficult to explain how the Hardwood complex, with its distinctive geochronologic and metamorphic signatures, came to be incorporated into the Penokean orogen. This study presents detailed field, petrographic and microstructural observations that may help constrain the origin and history of the Hardwood Gneiss. Peterson & Geiger (1990) identified three compositional units in the Hardwood: metabasite, amphibolite, and metapelite. The metapelite, a garnet-biotite schist, is clearly a distinct unit, exposed in the western end of the outcrop area, but our work suggests that the amphibolite and metabasite are both part of a heterogeneous igneous complex that included anorthositic, gabbroic and noritic horizons – perhaps a Neoarchean layered mafic intrusion. If this complex was of mantle origin, it could explain the absence of older Archean zircons. In addition to their compositional variety, the metamafic rocks display a wide range of metamorphic and deformational textures. In outcrop, they have a strong, apparently mylonitic, foliation that dips mainly NE but is somewhat variable in orientation and may be folded. In thin section, microstructures show that a combination of brittle and plastic deformation mechanisms contributed to the intense fabric. In plagioclase-rich horizons, the feldspars tend to be the largest crystals, apparently surviving as porphyroclasts. These show both cataclastic fracturing and highly distorted twins, a combination usually interpreted to indicate that deformation took place at mid-crustal depths and temperatures of ca. 500°, the brittle-plastic transition for feldspars. These intensely deformed rocks show evidence of only limited, and heterogeneous, recrystallization, either dynamic or static. This suggests that deformation was brief and that the rocks cooled quickly after deformation ceased. Garnet-bearing horizons within the mafic complex display especially remarkable textures. Clusters and trains of garnets, apparently broken -- and in some cases, shattered – are engulfed in a very fine-grained (<0.01mm) feldspathic matrix. The unusual shapes of some of the garnet fragments – including crescents and splinters – may indicate seismic fragmentation (Hawemann et al., 2019). The largest garnet fragments tend to have inclusion-free cores and ‘spongy’ poikilitic rims, while smaller fragments are commonly poikilitic throughout, with a notable 89 �concentration of opaque inclusions. In some cases, the edges of the small garnet fragments are so diffuse that they cannot be seen in plane light. Peterson & Geiger (1990) interpreted the poikilitic rims and small inclusion-rich garnets as records of a second metamorphic event, but we speculate that these are resorption features rather than overgrowths. ‘Spongy’ or ‘amoeboid’ poikilitic rims are known to form around granulite-facies garnets during the introduction of external fluids (Baxter et al., 2017), or when garnets are engulfed in pseudotachylyte melts (Austrheim et al., 1996). Because they form under disequilibrium conditions, such resorption rims are unlikely to yield reliable P-T results, and this could account for the large range of P-T conditions Peterson & Geiger (1990) suggested for their ‘M2’ metamorphic event. Given the shattered nature of the Hardwood garnets, we tentatively speculate that the very fine-grained material in which they occur could represent coseismic fault rock – either (devitrified) pseudotachylyte or/and ultracataclasite flushed with seismically-pumped fluids. In this interpretation, the Hardwood complex would have experienced only one high-P/T metamorphic event, followed by mylonitization, cataclasis and seismic faulting. If the quasi- brittle deformation of the feldspars – which seems to be part of the same event that shattered the garnets -- can be interpreted as occurring at ca. 500°, the deformation would have had to happen well after the granulite-facies event. However, feldspar plasticity can be suppressed in very dry rocks (e.g. Bjørnerud & Austrheim, 2004), so it is also possible that the seismic event(s) occurred under high-temperature conditions and possibly soon after the granulite facies metamorphism that formed the inclusion-free garnets. Whether any of these events occurred during the Penokean orogeny remains unclear. One possible constraint on the timing of the main foliation-forming event comes from the occurrence of an unfoliated mafic within a feldspathic layer in the Hardwood Gneiss on the south bank of the East Branch of the Sturgeon River. If this sill could be dated or linked geochemically with known mafic magmatic units in the region, this would establish the youngest possible deformation age for the Hardwood Gneiss. The Hardwood pelites are classic garnet-biotite schists, with asymmetric quartz-vein boudins and garnet ‘tails’ that suggest normal-sense shear along the NE-dipping foliation. Low- angle normal faulting would be the most efficient way to juxtapose deep crustal rocks like the Hardwood Gneiss against the shallower units that surround it. But the pelites, which represent supracrustal material and record amphibolite rather granulite-facies conditions, lie on the western edge of the Hardwood outcrop area, so top-to-the-east normal slip does not help explain how the high-pressure mafic units were brought up from depth. The area between the Felch Trough and the Niagara Fault is among the most structurally complex of parts of the Penokean/Yavapai orogen, with many anastomosing faults of different generations (Drenth et al., 2021). The orientations of structures within the Hardwood complex have almost certainly been altered since their formation by later faulting and tilting. For now, the Hardwood Gneiss remains a micro- terrane of unknown provenance within the Penokean orogen. References Attoh, K. & Klasner, J., 1989. Tectonics 8: 911-933. Austrheim, H., Erambert, M., & Boundy, T., 1996. Earth & Planetary Science Letters 139: 223-238. Ayuso, R., et al., 2018. Institute on Lake Superior Geology Proceedings 64: 7-8. Baxter, E., Caddick, M., & Dragovic, B., 2017. Rev. Min. & Geochem. 83, 469–533. doi: 10.2138/rmg.2017.83.15 Bjørnerud, M. & Austrheim, H., 2004. Geology 32: 765-768. Cannon, W.F., Schulz, K., Ayuso, R. & Mroz, T., 2018. ILSG Field Trip Guidebook 64: 1-38. Drenth, B., Cannon, W.F., Schulz, K., & Ayuso, R., 2021. Precam. Res. 369. doi: 10.1016/j.precamres.2021.106205 Hawemann, F., et al., 2019. Solid Earth 10: 1635-1649. doi: 10.5194/se-10-1635-2019 James, H., Clark, L., Lamey, C., & Pettijohn, F., 1961. USGS Professional Paper 310. Peterson, J. & Geiger, C., 1990. Journal of Geology 98: 273-281. 90 �Alteration Geochemistry Characterization and 3D Modeling of the Back Forty Volcanogenic Massive Sulfide (VMS) Deposit Stephenson, Upper Peninsula of Michigan, USA UPTON, Margaret1, MOOERS, Howard1, LARSON, Phillip2 1 Department of Earth and Environmental Sciences, University of Minnesota - Duluth, 1114 Kirby Drive, 102 Heller Hall, Duluth, MN 55812 2 Cleveland-Cliffs Hibbing Taconite Company. Hibbing, MN 55746 The Gold Resources Back Forty zinc-and-gold-rich polymetallic volcanogenic massive sulfide (VMS) deposit is located near Stephenson in the Upper Peninsula of Michigan. In general, VMS deposits are created in submarine environments when heated seawater circulates through oceanic crust and precipitates base and precious metals at or near the seafloor due to both cooling and neutralization of the ore fluid. In the process, host rock mineralogy and geochemistry are modified by both downwelling and upwelling hydrothermal fluids, which produces distinct alteration mineral assemblages and metasomatic changes within the host rock (Shanks and Thurston, 2012; Galley et al., 2007). Alteration mineral assemblages and their spatial distribution can be used to unravel the geochemical evolution of the system and help locate mineralization. The relationship between host rock and alteration mineralogy is not well understood or documented at the Back Forty Deposit but essential for understanding its genesis. This study 1) identifies the alteration mineral assemblage present at the Back Forty Deposit using lithogeochemistry results; 2) calculates the elemental gains and losses associated with hydrothermal alteration; 3) develops a working method for immediate qualitative alteration values from core logging; and 4) creates a model of the alteration zonation in coordination with the existing stratigraphy and mineralization. Core from nine drill holes (~ 2,950 meters), were logged to observationally identify alteration mineral assemblages, intensity, and their textural characteristics. The deposit, hosted in felsic pyroclastic rocks, shows mostly sericite alteration, which was used to establish an alteration intensity scale of 1-4 (1: weak, 5: intense). Major alteration mineral assemblages observed were sericite ± silica ± chlorite. Sericite alteration is pervasive throughout the deposit (2.5-3.5) with silica alteration intensity ranging from 1-2 and a few areas of silica flooding (3.5-4.5). Weak to moderate (1.5-2.5) chlorite alteration occurred throughout the deposit within the host rhyolite crystal tuff units as spotty chlorite coarse-grained agglomerations. Lithogeochemistry (1,300 count) was evaluated using the alteration box plot (Large et al., 2001) and the isocon mass balance method (Grant, 1986) (fig. 1), which are essential in quantitative assessment of chemical changes associated with alteration mineral assemblages and their spatial distribution, and the identification of hydrothermal fluid pathways and mineralization vectors within the deposit. In addition to using isocon results, alteration box plot results were modeled based on sericite, chlorite, and total alteration. The production of cross sections based upon this numerical modeling identify the alteration mineral zonation and its relative extent; this model is evaluated to determine the relationship between massive sulfide mineralization and alteration intensity. From these results, downhole core logging of alteration assigned numeric values (“quick log”) is evaluated as a method to make fast-paced exploration decisions while awaiting longer lead-time lithogeochemical results. By leveraging the process and combination of core logging for alteration mineralogy and intensity paired with geochemical analysis, it may be possible to determine the origin direction of hydrothermal fluid flow associated with mineral deposition and aid in future exploration efforts to locate additional mineralization on the Back Forty Deposit property. 91 �Results from this study show the sericite alteration is most significantly related to Zn and Cu mineralization, whereas the chlorite alteration is most associated with Ag, Au, and Pb. Distinctly depleted species associated with sericite alteration include Ba, Sr, Na2O, Rb; with chlorite commonly depleted in Br, Ba, Sr, Na2O. Least v. Intense Sericite Alteration 50 45 45 Be Au Ge Zn Ga U Cu 40 35 More Altered Cs Dy Ce La Ag Ni Cr 20 Tl Hf Sn Sc TiO2 10 MgO As Yb Tl Mo Zr Pr Pr Hg Cd U Ir 15 Lu Sc 10 Hf V TiO2 Te Ba Tb MnO Br Eu Ga Cs Co Nd K2O Be In 20 Er Ho Y Cr2O3 Nb Ge y = 0.996x R² = 0.996 Na2O CaO 10 15 20 25 30 5 NdYb Sm Br Rb Gd Dy Tm Eu Bi Ba AL2O3 K2O 35 40 45 50 Cr Ta Sr y = 1.067x R² = 0.999 Na2O CaO BaO Re 0 Least Altered Th MgO P2O5 0 Lu SiO2 La Ce Ir Ho Sr 5 Ni Pb In Cd 0 25 BaO Tb V Co Bi Gd Er Hg Fe2O3 5 Rb Pb Y MnO Sb Cu Fe2O3 Sm P2O5 15 Tm Cr2O3 Ta Se W 30 W Zr 25 Zn 35 SiO2 Nb 0 40 Th 30 Least v. Intense Chlorite Altered 50 5 10 15 20 25 30 35 40 45 50 Least Altered Figure 1. ISOCON plot of selected elements used to compare elemental gains and losses between least and most altered samples. Isocon line of best fit is defined by relative immobile. Species above the isocon line are enriched; below are depleted (Grant, 1986). References Aquila Resources (now Gold Resources), data current as of April 2021. Galley, A., Hannington, M., Jonasson, I., 2007. Volcanogenic Massive Sulphide Deposits. Geological Survey of Canada, Special Publication 5: 141-161. Grant, J. A., 1986. The Isocon Diagram: A Simple Solution to Gresens' Equation for Metasomatic Alteration. Economic Geology, v. 81: 1976-1982. Large, R. R., Gemmell, B.J., Paulick, H., 2001. The Alteration Box Plot: A Simple Approach to Understanding the Relationship between Alteration Mineralogy & Lithogeochemistry Associated with Volcanic-Hosted Massive Sulfide Deposits. Economic Geology, v. 96: 957-971. Shanks, W.C.P., Thurston, R., 2012. Volcanogenic Massive Sulfide Occurrence Models. USGS Scientific Investigations Report 2010–5070–C: 363. 92 �Summary of the 2022 ILSG Field Trip to Iceland UPTON, Margaret1, LARSON, Phillip2, MACTAVISH, Allan3, HINZ, Peter4 1 Department of Earth and Environmental Sciences, University of Minnesota - Duluth, 1114 Kirby Drive, 102 Heller Hall, Duluth, MN 55812 2 Cleveland-Cliffs Hibbing Taconite Company. Hibbing, MN 55746 3 AGC GeoConsulting, 777 Red River Road, Thunder Bay, ON P7B IJ9 4 Retired, Ontario Ministry of Energy, Northern Development and Mines, Thunder Bay, ON During Summer of 2022 (July 26-August 9), a group of 16 people set out to tour the diverse and awe-inspiring geology of Iceland, led by ILSG representative geologists Phil Larson, Peter Hinz, and Allan MacTavish. The 15 day trip held many surprises for all involved, including the worst stretch of weather Phil has experienced in Iceland (of 11 visits!) as well as a once-in-a-lifetime experience to see a volcanic eruption. In addition to the trip leaders, the group of 16 people included 3.5 professional geologists, 1.5 graduate students, one retiree, one Goldich Medal laureate, and 9 members of the Minnesota Geological Society. Stops throughout the trip focused on a wide range of topics: • Volcanism, both historical and the 2021 Geldingadalir eruption; Figure 1. Photo credit: Tom Hart • Icelandic cuisine, lore, and the historical and cultural evolution of the nation; • Environmental geochemistry of subsurface and near-surface processes; • Volcanic flows, igneous petrology for mineralogy and volcanic textures; • Geothermal energy and its uses; • Hydrology and hydrologic events related to glaciers and volcanics; • Geomorphology as it relates to ecology, volcanics, and glaciers • Wind, water, and glacial erosional features; glacial nomenclature By special arrangement, the trip was scheduled to overlap with the onset of the 2022 Meradalir eruption (fig.1). An advance party made a midnight scouting foray to the vent site before a Force 13 gale descended on the island. 93 �This presentation summarizes the highlights from the trip (fig.2). Featured locations include the Fagradalsfjall eruptions on the Reykjanes Peninsula, the Vestmannaeyjar Islands, climbing atop and viewing the Laki fissure from above, trekking to the highlands to view Askja and its pumice fields, the Jökulsárgljúfur canyon and scablands, free roadside hákarl stands, being lowered into a dormant magma chamber, a sampling of geothermal pools, plus the many epic waterfalls along the way! Figure 2. Generalized map of the trip route. 94 �GEOHERITAGE AS AN EDUCATIONAL TOOL TO EXPLORE RELATIONSHIPS WITH LAND AND WATER IN THE KEWEENAW VYE, Erika1 and ROSE, William2 1 Great Lakes Research Center, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 Department of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 2 Geoheritage is an evolving field in the United States that considers the protection, interpretation, and management of geologic features with significant scientific, educational, cultural, or aesthetic value (Brocx & Semeniuk, 2007; Geological Society of America, 2017; National Park Service & American Geosciences Institute, 2015; Reynard & Brilha, 2017). Geoheritage strongly emphasizes the importance of the varied personal values people have for geologic features and the wide-ranging relationships we have with landscapes. As such, geoheritage is an effective geoscience communication tool affording place-based learning experiences that nurture our sense of place, deepen our Earth science literacy, and inspire stewardship and protection of our place. This presentation explores geoheritage education and outreach initiatives in Michigan’s Keweenaw Peninsula for both formal and informal learning communities. The Keweenaw Peninsula sits at the heart of the Midcontinent Rift and is renowned for the world’s largest accessible native copper deposit and Lake Superior, the largest freshwater lake on Earth. These geologic processes and features have fostered varied human relationships with the landscape, including the oldest metal workings in the Western Hemisphere and the European immigration wave of 18401910 triggered by the Copper Boom. This intersection of deep time, industrial, and cultural heritage has been the focus of teacher professional learning institutes and student internship experiences that explore the compelling geoheritage of our place. These programs: a) focus on complex environmental issues rooted in Earth systems processes of importance within the community, b) emphasize strong community partnerships that bring together varied values and perspectives of our place; c) explore other ways of knowing about the dynamic and interconnected geologic and human stories that serve as the foundation of the landscape’s past, present, and future through equitable knowledge exchange, and d) elevate Earth science literacy for educators and students by connecting the underpinning geology to current environmental issues with wide-ranging impacts in our communities today such as cultural identity, subsistence uses, recreation, and sense of place. The geologic formations of the Midcontinent Rift are beautifully exposed in the Keweenaw for researchers, teachers, students, and geotourists. As the Keweenaw shifts from an extractive industrial economic past, geoheritage initiatives support a future based on education, conservation, and sustainable tourism. Current initiatives in our community include a) the development of geotourism opportunities - Keweenaw Geotours, b) strong partnerships with local conservation groups to maintain access to world-class geosites that provide outstanding Earth science learning opportunities, and c) exploration of recreational opportunities including the concept of a shoreline hiking trail following the high water mark of Lake Superior. Geoheritage education and outreach opportunities help foster a culture of stewardship, increase Earth science literacy, and provide opportunities to share our varied relationships with land and water. 95 �Figure 1. Teachers and students explore the geoheritage of the Keweenaw by land and water. References Brocx, M. and Semeniuk, V., 2007. Geoheritage and geoconservation - history, definition, scope and scale. Journal of the Royal Society of Western Australia, 90: 53-87. Geological Society of America 2017. GSA Position Statement: Geoheritage. Retrieved from: https://www.geosociety.org/documents/gsa/positions/pos20_Geoheritage.pdf. National Park Service and American Geosciences Institute 2015. America’s Geologic Heritage: An Invitation to Leadership. NPS 999/129325. National Park Service, Denver, Colorado. Reynard, E. and Brilha, J., 2017. Geoheritage: Assessment, protection, and management. Elsevier, ISBN: 9780128095317. 96 �U/Pb geochronology and zircon petrochronology of Paleoproterozoic magmas from the Marshfield terrane Penokean Orogen, Wisconsin WEBER, Evan1, LODGE, Robert W.D.1, MARSH, Jeffrey2 1 Department of Geology and Environmental Science, University of Wisconsin-Eau Claire, Phillips Hall Eau Claire, WI 54701 2 Department of Earth Sciences, Laurentian University, 933 Ramsey Lake Rd, Sudbury, ON P3E 6H5, Canada This study presents U-Pb, Hf-Lu, and trace isotopic element data from zircons obtained from volcanic and intrusive rocks from the Paleproterozoic Penokean magmas within the Marshfield terrane in northern Wisconsin. The Penokean Orogen hosts both the Proterozoic Pembine-Wausau and the Archean Marshfield terranes. The Eau Pleine Shear Zone is interpreted as the paleosuture zone between these two terranes (Sims et al., 1989). Both terranes host volcanic and intrusive rocks that were formed during the Penokean orogen. The Pembine-Wausau terrane is a juvenile arc system that was developed through subduction during the Penokean orogen that accreted against the Superior craton. The volcanic rocks in this terrane are tholeiitic and calcalkaline in nature (Schulz and Cannon, 2007). The Marshfield terrane is thought to be an accreted fragment of an Archean craton that collided with the Pembine-Wausau terrane and the Superior craton (Klier, 2019). The Marshfield terrane is mainly comprised of gneisses that underlie Early Proterozoic volcanic rocks (Sims et al., 1989), but due to poor exposure of these rocks this terrane is poorly understood. This study aims to provide a better understanding of the volcanic terranes in the region to improve regional models of the southern portion of the Penokean orogen. Samples were collected from Big Falls and other locations within the Eau Claire volcanic complex, as well as from granites and gneisses exposed in Black River Falls. Zircons from these samples were then analyzed at Laurentian University (Sudbury, Ontario, Canada) via Split-Stream Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LASS-ICP-MS) to obtain U-Pb, HfLu, and trace isotopic element data. Results reveal complex age relationships and basement architectures. The Big Falls gneiss, part of the Eau Claire volcanic complex lying south of the Eau Pleine Shear Zone (Fig. 1), resulted in an interpreted U-Pb age of 1874.7±2.1 Ma (Fig. 1) which is consistent with VMS-forming events in the Pembine-Wausau terrane. Zircon trace element geochemistry from the Eau Claire volcanic complex indicate rocks formed from a hydrated but reduced melt. This melt may have occurred in a back-arc setting where decompression occurred in a metasomatized mantle, which is characteristic of back-arc signatures. Hf-Lu isotopic data from the Eau Claire volcanic complex show the rocks here lack an Archean inheritance. The data from the Eau Claire volcanic complex was compared to a granite intrusion in Black River falls and both the Eisenbrey and Lynne VMS deposits in the Pembine-Wausau terrane. Based on Hf-Lu data, the Black River Falls granite showed inheritance of basement, which is expected based on field relationships with Archean rocks from the Marshfield terrane. The Eisenbrey and Lynne deposit have juvenile signatures which is characteristic of an oceanic arc system. According to trace isotopic element data, the VMS deposits also formed from a more oxidized and hydrated melt which is a similar geodynamic setting seen in the Eau Claire volcanic complex. Since we would expect basement inheritance in the Eau Claire volcanic complex, these results question what is known about the Marshfield terrane and its relationship to the Penokean. 97 �Figure 1. Geologic map of Eau Claire and Chippewa Falls area highlighting the location of Big Falls alongside a concordia diagram plotting the age of Big Falls at 1874.7±2.1 Ma. Cathodoluminescence imaging of individual zircons are also shown with their corresponding ages. References Brown, B.A., 1988. Bedrock Geology Map of Wisconsin (Regional Map Series: West-Central Sheet), University of Wisconsin-Extension Geological and Natural History Survey, Scale: 1:250,000. Klier, J.J., 2019. The Marshfield Terrane: Redefinition of Origin Through Zircon Geochronology and Geochemistry [MSc thesis]: Ball State University: 115. Schulz, K.J. and Cannon, W.F., 2007. The Penokean orogeny in the Lake Superior region. Precambrian Research 157: 4-25. Sims, P.K., Van Schmus, W.R., Schulz, K.J., and Peterman, Z.E., 1989. Tectonostratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: Canadian Journal of Earth Science, v. 26: 2145-2158. Zi, J.-W., Sheppard, S., Muhling, J.R., and Rasmussen, B., 2021. Refining the Paleoproterozoic Tectonothermal History of the Penokean Orogen: New U-Pb Age Constraints from the Pembine-Wausau terrane, Wisconsin, USA: GSA Bulletin, v. 134: 776–790. 98 �The Use of Electric Pulse Disaggregation Technology to Recover Nickel Metal from Nickel Sulfide Ore Deposits WEIBLEN, Paul1 1 Minnesota Geological Survey (Retired), 2609 West Territorial Road, St. Paul, MN 55114 All metals, except for the noble metals like gold, occur in nature as metal sulfides. The chemical process “Plat Sol”1 can be used to recover nickel metal from nickel sulfide ores. The demand for nickel metal has increased dramatically due to the need for nickel metal for electric vehicle batteries. Elon Musk, always ahead of the curve, has signed an agreement with Talon Metals to be the sole recipient of any nickel metal they produce. Similarly, the Biden Administration is encouraging a transition from fossil Fuel vehicles to electric vehicles.2 However, a particle size of less than a millimeter is required for the feed to the Plat Sol process. Electric Pulse Disaggregation Technology3 provides much more efficient and less expensive method than conventional crushing and grinding for reducing the particle size of ore samples. Figure 1 provides details on the disaggregater. Inside the 3D printed gray cap on the left below is a stainless steel hemisphere with a pointed electrode projecting upward. On the right, is a black 3D printed cap with an electrode like the one above. When the two caps are screwed together, a sphere is formed. The electrodes are separated ~ 5 mm forming a spark gap. The two hemispheres are filled with water and inch-sized sample fragments. When the 50KV power supply is turned on the discharge across the spark gap vaporizes the water, which in turn separates different minerals along their grain boundaries. Examples of “zapped” Talon Metals nickel sulfide ore will be shown. Figure 1. Image of the disaggregator set up. References Google “Plat Sol” https://www.whitehouse.gov/briefing-room/statements-releases/2021/08/05/fact-sheet-president-bidenannounces-steps-to-drive-american-leadership-forward-on-clean-cars-and-trucks/ https://www.researchgate.net/project/Electric-pulse-disaggregation-and-hydroseparation-for-mineral-processing *** Abstract Withdrawn*** 99 � https://digitalcollections.lakeheadu.ca/files/original/0b0e110830002a4043b2d65b71c5ca51.pdf 2cbbb59065186547c55e7817dcd81e3e PDF Text Text 69th ANNUAL MEETING Eau Claire, Wisconsin — April 24-25, 2023 INSTITUTE ON LAKE SUPERIOR GEOLOGY Part 2 — Field Trip Guidebooks �Thank you to our sponsors! A SPECIAL THANK YOU TO OUR INDIVIDUAL CONTRIBUTORS: FREDERICK CAMPBELL, VAL CHANDLER, JIM DEGRAFF, THOMAS ERICKSON, TOM FITZ, DAVE GOOD, PAULA LEIER-ENGELHARDT, ALLAN MACTAVISH, BOB MAHIN, GORDON MEDARIS JR., JIM MILLER, STEVEN PINTA, TOD ROUSH, AND GERRY WHITE i �Proceedings of the 69th ILSG Annual Meeting – Part 2 69th ANNUAL MEETING INSTITUTE ON LAKE SUPERIOR GEOLOGY April 24-25th Eau Claire, Wisconsin HOSTED BY Rob Lodge, Esther Stewart, Carsyn Ames Co-Chairs University of Wisconsin- Eau Claire and Wisconsin Geological and Natural History Survey Proceedings - Volume 69 Part 2 – Field Trip Guidebooks Compiled and edited by Rob Lodge Cover Photos. Upper — Photograph of E.O. Ulrich taking notes in the field describing the Cambrian Mount Simon Formation in the Chippewa Falls region in 1913. Lower — Photograph of geologists E.F. Bean and E.C. Edwards fording the Eau Claire River at Morrison’s Ford in 1919. iii �Proceedings of the 69th ILSG Annual Meeting – Part 2 69th INSTITUTE ON LAKE SUPERIOR GEOLOGY VOLUME 69 CONSISTS OF: PART 1: PROGRAM AND ABSTRACTS PART 2: FIELD T RIP GUIDEBOOK Trip 1: PRECAMBRIAN GEOLOGY OF THE CHIPPEWA RIVER VALLEY Trip 2: WISCONSIN’S PALEOZOIC STRATIGRAPHY AND TOUR OF CRYSTAL CAVE Trip 3: PRECAMBRIAN GEOLOGY OF THE EAU CLAIRE RIVER VALLEY Trip 4: QUATERNARY GEOLOGY AND GEOMORPHOLOGY OF THE EAU CLAIRE REGION Reference to material in Part 2 should follow the example below: Lodge and Hooper, 2023. Precambrian geology of the Chippewa River Valley: A transect through the western Marshfield Terrane. in Lodge, R.W.D. (Ed.), Institute on Lake Superior Geology Proceedings, 69th Annual Meeting, Eau Claire, Wisconsin, Part 2 – Field Trip Guidebooks. v.69, part 2, p.1-26. Published by the 69th Institute on Lake Superior Geology and distributed by the ILSG Secretary: Pete Hollings - ILSG Secretary Department of Geology Lakehead University 955 Oliver Road Thunder Bay, ON P7B 5E1 Canada Email: peter.hollings@lakeheadu.ca ILSG website: www.lakesuperiorgeology.org ISSN 1042-9964 iv �Proceedings of the 69th ILSG Annual Meeting – Part 2 Part 2: Field Trip Guidebooks Table of Contents Page Field Trip 1: Precambrian geology of the Chippewa River valley: A transect through the western Marshfield Terrane Field Trip 2: Wisconsin’s Paleozoic stratigraphy and tour of Crystal Cave Field Trip 3: Precambrian Geology of the Eau Claire River Valley: Re-discovering the Eau Claire Volcanic Complex Field Trip 4: Quaternary Geology and Geomorphology of the Eau Claire Region v 1 27 48 71 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Field Trip 1 – Precambrian geology of the Chippewa River Valley: A transect through the western Marshfield Terrane Robert W.D. Lodge and Robert L. Hooper Department of Geology & Environmental Science, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54701 of the 18.2 Mt Back Forty VMS deposit in Michigan, easing of the Wisconsin sulfide mining moratorium in 2017, and a recent national push for securing critical mineral resources. However, this has also highlighted the lack of modern datasets, notably lithogeochemistry, on these deposits that could be used to further our knowledge of the mineral-forming systems in the VMS belt. The Pembine-Wausau terrane has received most of the historic and recent attention since it hosts approximately 150 million tonnes of known VMS mineralization. However, little attention has been given to the Penokean volcanic deposits that overprinted the Marshfield Terrane that are presented in this guidebook. DeMatties (2022) recognized the gap in knowledge for these Penokean volcanic deposits within the Marshfield Terrane, also called the Eau Claire Volcanic Complex, and highlighted their exploration potential. Introduction The erosional outliers of Precambrian bedrock in the Chippewa River Valley represent the southernmost extent of the Canadian Shield before it is completely covered by Paleozoic sedimentary strata. The rocks exposed here are part of the Paleoproterozoic Penokean Orogeny, a collisional orogen that resulted from the accretion of the Pembine-Wausau and Marshfield terranes onto the (present-day) southern margin of the Superior Province. This region was last visited by members of the Institute of Lake Superior Geology in 1980 when a field trip through the region was conducted by Paul Myers (Myers et al., 1980). Since this time, there has been ‘new’ U/Pb data collected by the USGS (Sims et al. 1989) and others (Van Wyke et al, 1997; Klier, 2019), regional syntheses of the Penokean volcanogenic massive sulfide (VMS) mineralization (DeMatties 1989; 1994; 2018; 2022), maps published by government surveys (Mudrey et al, 1987; Brown 1988), and orogenwide tectonic model (Shultz and Cannon, 2007) that is being revisited based on new U/Pb data (Zi et al., 2021). After forty years of advancing our knowledge of the Penokean Orogen, it is worth touring again. The portion of the Marshfield terrane that is visited in this guidebook is well known, but grossly understudied and much of its regional context is unknown. Students from the University of Wisconsin-Eau Claire have been visiting many of the locations in this guidebook for decades to learn how to map and describe rocks in the field, measure structures and interpret geologic histories, and learn the basic mechanics of field work. Faculty, students, and alumni from Eau Claire consider these outcrops classic. This guidebook will (re-)introduce these rocks and provide an updated view on their context to the Marshfield terrane and Penokean Orogen. Ongoing research in this region hopes to expand the lithogeochemistry and zircon petrochronology database to better delineate the The Penokean Orogen is perhaps best known for hosting numerous VMS deposits. The passing of the “Prove-it-first” law, or sulfide mining moratorium, in 1997 effectively shut down mineral exploration and mining in Wisconsin. One of the most complete descriptions of several deposits was published by the Institute of Lake Superior Geology (LeBarge, 1996). More recently, the mineral exploration industry has been reinvigorated because of the 2002 discovery 1 �Proceedings of the 69th ILSG Annual Meeting - Part 2 geodynamic evolution and crustal architecture of this region. Determining the presence or absence of Archean basement throughout the Marshfield terrane will help refine terrane boundaries and improve our understanding of the metallogeny of the region to assist in future mineral exploration efforts. in a suprasubduction zone setting and are now structurally juxtaposed along the southern edge of the Archean Superior Province during the earliest phases of forming the Columbia, or Nuna, supercontinent (LaBerge and Myers, 1984; Sims et al., 1989; Schulz and Cannon, 2007). The orogen is host to at least 150 million metric tonnes (Mt) of VMS and associated mineralization (DeMatties, 1994, 2018) but remains one of the more poorly understood and underexplored mineral districts in North America. Regional Geology The Paleoproterozoic Penokean Orogen (ca. 1.8 Ga) in the Lake Superior region (Figure 1) is a classic Precambrian orogenic belt comprised of dominantly sub-marine volcanic rocks and associated plutons. The Penokean rocks formed The Penokean Orogen has been divided into the Interior and Exterior domains. The Exterior Figure 1 – Geologic map of the major tectonic assemblages and major structures of the Penokean Orogen. Notable and important abbreviations that are important for this guidebook are EPSZ, Eau Pleine shear zone; NFZ, Niagara fault zone. Figure from Shultz & Cannon (2007). 2 �Proceedings of the 69th ILSG Annual Meeting - Part 2 domains are sutured to the Superior Craton by the Niagara fault zone (Figure 1). The Exterior domain consists of passive margin, rift, and forearc basin sediments and Archean crustal blocks from the Superior Province that were folded and faulted in the foreland part of the orogen. The Interior Domain consists of two accreted terranes, the Pembine-Wausau and Marshfield terranes, that are sutured by the Eau Pleine Shear zone (Figure 1). The PembineWausau terrane is a composite accreted oceanic arc overprinted by continental-margin magmatism and hosts numerous VMS deposits and occurrences (DeMatties, 1994; Shultz & Cannon, 2007) (Figure 2). The Marshfield terrane is composed of Archean crustal fragments of unknown origin that were overprinted by Penokean magmas during the orogen (Figure 2) and is described in more detail in the section to follow. Shultz and Cannon (2007) synthesized tectonic events during the Penokean Orogeny based on a detailed compilation of lithologic, structural, sedimentological, isotopic, and geochronological datasets. This classic model proposed that an oceanic arc, now referred to as the PembineWausau terrane, collided with the southern Superior Province around 1880 Ma. Following a subduction flip from south-directed to northdirected subduction, continental arc magmatism and back arc extension followed until about 1850 Ma when convergence with an Archean crustal block, known as the Marshfield Terrane accreted to the southern edge of the Wausau- Pembine Terrane along the Eau Pleine Shear Zone (ESPZ). Sedimentation related to this convergence in a foreland basin setting continued until about 1835 Ma. The end of the Penokean orogen was constrained by a series of undeformed posttectonic plutons dated at 1830 Ma which stitched the terranes. Figure 2 – Schematic tectonic evolution of the Penokean Orogen provided by Shultz and Cannon (2007) based on geophysical, sedimentological, and geochronological complications. contradictory data came when Quigley (2016) obtained a high-precision U/Pb zircon age of 1832.98 ± 0.52 Ma from a rhyolite at the Back Forty deposit via CA-ID-TIMS. The other analyzed VMS deposits across the PembineWausau terrane by Quigley (2016) provided consistent U/Pb zircon ages ca. 1875 Ma and supported the Shultz and Cannon (2007) tectonic model. Additional U/Pb zircon ages from volcanic units (Beecher Formation) and plutonic rocks (Dunbar Gneiss, Newingham Tonalite) in the eastern part of the orogen by Zi et al. (2021) However, this classic tectonic model for the evolution of the Penokean orogen has recently been re-evaluated in light of new U/Pb data obtained throughout the orogen. The first 3 �Proceedings of the 69th ILSG Annual Meeting - Part 2 supported the younger extensional tectonic event proposed by Quigley (2016). These new ages resulted in a revised Penokean tectonic model where long-lived northward subduction along a continental margin with repeated extensional and contractional regimes in response to retreat and advance of the subducting oceanic plate (Figure 3). Weber and Lodge (2022) obtained a U/Pb age of 1831.4 ± 2.0 Ma on the dacite unit hosting the Eisenbrey deposit in the western part of the orogen, suggesting that this second VMS forming event was widespread. A summary of the geochronology is presented in Figure 4. part of the Marshfield terrane and lie immediately south of the Eau Pleine Shear Zone. Current tectonic models suggest that the Marshfield Terrane represents an Archean microcontinent of uncertain origins (Sims et al., 1989; Schulz and Cannon, 2007; Zi et al., 2021). Some of the earliest work on the terrane by Sims et al. (1989) noted only eight Archean U/Pb ages from isolated outcrops along the Wisconsin, Black, and Chippewa Rivers, many of which were compiled from unpublished sources. One of those was the gneiss exposed at Jim Falls (Stop 3 in this guidebook) which was dated at 2522 ± 22 Ma. Current tectonic reconstructions usually have Paleoproterozoic volcanic rocks in the Marshfield terrane being deposited on Archean basement at about 1870–1860 Ma. The Paleoproterozoic volcanic sequence is referred to as the Eau Claire Volcanic Complex by DeMatties (2018; 2022) and are preserved only as erosional remnants. The Eau Claire Volcanic Complex consists principally of an interlayered sequence of felsic to mafic volcanic rocks, dacite porphyry, and a variety of clastic and chemical sedimentary rocks (Sims et al., 1989). Some conglomerates contain granitic gneissic clasts that were interpreted to be Archean (Myers et al. 1980), but no definitive ages were determined on the clasts. Throughout the Marshfield terrane there are various Paleoproterozoic intrusions of gabbro, diorite, and tonalite. These have U/Pb ages of 1835-1865 Ma (Sims et al., 1989; Van Wyck and Johnson, 1997; Weber and Lodge, 2022). Otherwise, our knowledge of the Archean basement of the Marshfield terrane and associated Paleoproterozoic volcanic rocks remains as sparse as the outcrop exposures. Figure 3 - Schematic illustration of the revised tectonic model of the Penokean Orogen. Figure is from Zi et al. (2021). Abbreviations: NF—Niagara fault zone; EPSZ—Eau Pleine shear zone.Marshfield Terrane The study of the Marshfield terrane remained stagnant until new U/Pb and Lu-Hf isotopic data from zircons was published as a masters thesis (Kleir, 2019). The new isotopic data in the Marshfield Terrane collected from the Chippewa and Yellow River valleys will be presented at various stops on this field trip. In our opinion, one of the most significant results was that the “Archean” rocks from the Jim Falls region of Marshfield Terrane This guidebook visits field sites from the northwestern exposures of rocks interpreted to be 4 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 4 - Time-space plot for the tectonic components of the Penokean Orogen. Plot is from Zi et al. (2021). See citation for references on data sources. Sims et al. (1989) is a metasedimentary rock that has a significant proportion of Paleoproterozoic zircons (Kleir, 2019). While the data clearly indicates the presence of Archean rocks in the sedimentary source region, the sedimentary provenance does not require that Archean rocks represent the basement architecture in the northern part of the Marshfield Terrane. U/Pb ages from the northern part of the Marshfield Terrane collected in the Chippewa and Yellow River areas are interpreted as Paleoproterozoic in age (~1.83-1.88 Ga) and Hf isotopies indicate a juvenile source (without Archean contributions). This finding raises questions about the extent of the Archean basement in the Marshfield Terrane and consequently, the basement architecture in 5 �Proceedings of the 69th ILSG Annual Meeting - Part 2 the region. Preliminary geochemistry from Klier (2019) and our ongoing studies in the region show interesting trends that will help distinguish petrogenetic processes. Figure 5 highlights the REE trace element characteristics of these deposits and their application to each stop in subsequent sections below. thermometry determined temperatures between 719-769°C (Hannack and Radwany, 2018). A rutile U/Pb age of 1835 Ma from Sims et al. (1989) in the Eau Claire Volcanic Complex (Big Falls – Fieldtrip 3 in this volume) may indicate the timing of metamorphism since new zircon U/Pb age from the same region provided a crystallization age of ~ 1875 Ma (Weber and Lodge, 2022). Regional metamorphism in this region is at lower to upper amphibolite facies. Hornblendeplagioclase thermo-barometry from gneisses in the Chippewa River valley indicate metamorphism occurred at temperatures between 606-646°C and pressures between 5.74-6.64 Kbar (Hafften and Radwany, 2018). A sample of amphibolitic gneiss from the Eau Claire Volcanic Complex using the edenite-richterite Field Trip Stops The overall objective to this guidebook is to tour the Precambrian exposures of the Marshfield terrane along a southwest-northeast transect as exposed in the Chippewa River Valley. Starting within the city of Chippewa Falls, the trip will work its way to the northwest along the river and presumably get closer to the terrane boundary at the Eau Pleine Shear Zone. Stops 1-4 and 6 are all within the Marshfield Terrane, whereas Stop 5 is considered the southernmost exposure of the Pembine-Wausau Terrane. Fieldtrip stops are summarized in Figure 6. New data have us questioning what we know about the Marshfield Terrane. For example: Where exactly is the northern boundary of the Marshfield terrane in the Eau Claire region, and how much of the Marshfield Terrane, as currently defined, has an Archean basement architecture? Most of the locations in this guidebook are at the downstream side of hydro-electric dams. These areas are prone to sudden flooding and the upmost caution and careful planning should be used prior to visiting these locations. In addition, rocks here are uneven and slippery especially when wet. To access larger sections of outcrops, low water conditions or ladders (temporary bridges) may be required. In addition, all locations in this region may contain poisonous plants (e.g. nettle, poison ivy) and black-legged ticks that can transmit diseases. While this is unlikely to be a concern in early spring during the 2023 ILSG conference, future users of this manual should plan appropriately. Figure 5 - Trace element diagrams from the rocks in the Chippewa River valley region. Data from Cornell is preliminary data from ongoing projects whereas the remainder is from Klier (2019). (A) Classification diagram from Pearce (1996) showing protolith compositions. (B) Primitive mantle-normalized rare earth element diagram using normalizing values from Sun and McDonough (1989). 6 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 6 - Regional geology of the Chippewa Falls and Eau Claire region showing fieldtrip stops and approximate location of the Eau Pleine Shear zone. Rocks to the south of the Shear Zone are interpreted to be part of the Marshfield Terrane, whereas rocks to the north are part of the Pembine-Wausau terrane. Figure compiled from Mudrey et al. (1987) and Brown (1988). 7 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Stop #1 – Nonconformity at Irvine Park Claire and Chippewa Falls region are some of the southernmost exposures of the crystalline basement in the Lake Superior region before it disappears beneath the undeformed Paleozoic sedimentary strata. This is one of the many exposures of the “Great Unconformity” that is present throughout this region. Details of this unconformity in this region is described in detail in the most recent ILSG guidebook presented in Eau Claire (Chan et al. 1991) and is summarized below. Lat: 44.9542° Long: -91.3972° Precambrian Unconformity The Precambrian- Cambrian boundary is represented by a highly variable surface in the mid-continent area. In west-central Wisconsin, the Precambrian surface forms an extensive planation surface with a regional SW dip of less than 1 degree. Archean iron formations in the Black River Falls region and Proterozoic quartzites throughout the state, most famously the Baraboo Syncline, form isolated monadnocks on the peneplain. The peneplain was mantled by a layer of paleosols as much as several hundred feet thick. In some areas, Cambrian rocks directly rest upon barren, moderately weathered Precambrian rocks. Considering the low paleolatitude of the continent during the Cambrian, deep weathering of the Precambrian surface must have occurred before the Upper Cambrian deposition. The Precambrian basement, however, shows variable degrees of weathering and the weathering is complicated by potassium metasomatism overprinting associated with Silurian and Devonian K-rich basinal brines (Lui, 1997; Lui et al., 2003). Potassium metasomatism along the unconformity is responsible for the development of illite, interlayered I/S and authigenic Kfeldspar in both saprolites and in the Cambrian rocks in the Chippewa River Valley. Where the Precambrian is mafic (gabbros, amphibolites and gneisses) the potassium metasomatism commonly produces a distinctive bright bluegreen clay (celadonite) seen at Stop 2 on this field trip and at Big Falls (Fieldtrip 3 in this guidebook). These potassic brines have been The outcrop described at this stop is located along the east bank of Duncan Creek within Irvine Park in Chippewa Falls. Upon entering the park, drive north on Irvine Park Drive past the zoo and bison enclosure until the inter-section with Bear Den Road. There is ample parking in this area near the intersection that crosses Duncan Creek to the east and find the small foot trail that leads northward to the outcrop. Potential hazards include poisonous plants and ticks, but they are unlikely to be a problem in early spring. There is also uneven and potentially wet ground. The purpose of this location is to highlight the conditions that are impeding the study of the Precambrian bedrock in the region. The Eau 8 �Proceedings of the 69th ILSG Annual Meeting - Part 2 implicated in the formation of MVT deposits in the Tri-state region (Aleinkoff et al., 1993). At this location (and numerous others) where the Cambrian formations are in contact with Precambrian plutonic rocks, the basement is heavily spheroidal weathered (Photo 1, Figure 7) and is generally deeply altered to kaolinite saprolite and then metasomatically altered to illite I/S and authigenic Kspar. Mt. Simon Formation sandstone and conglomerate fill the wedges among the spheroids. In some areas such as Little Falls and Big Falls in Eau Claire County (Fieldtrip 3, this volume) or Rock Dam in Jackson County, Cambrian sandstones rest upon Proterozoic amphibolite and meta-rhyolites that are only partially altered. Mount Simon Formation is a coarse-grained, medium to thick-bedded quartz pebble conglomerate. The topographic relief on the Precambrian surface was probably only a few meters as sedimentary channels are typically less than 1 meter deep. The presence of trace fossils (rusophycus and Climactichnites, or trilobite burrows/tracks; Photo 2) and planar and bipolar cross-bedding (Photo 3) suggest a littoral or shallow marine tidal flat environment of deposition for the lower part of the formation. The upper part of the Mt. Simon Formation contains feldspathic quartz arenite with smallscale ripple bedding, brachiopod fragments (lingula sp.), and worm trails (planolites) The Photo 2 - Climactichnites fossil from the lower Mt. Simon Formation collected along the Chippewa River near downtown Eau Claire. Climachtinites trace fossils are typical of tidal flats in the Cambrian. Field of view is ~1m across. Photo 1 – Irvine Park outcrop photograph showing nonconformity between Cambrian Mt. Simon Formation (above) and Paleoproterozoic trondhjemite (below). Photo courtesy of Scott Clark (UW-Eau Claire Cambrian Mount Simon Formation The sediment above the unconformity consists largely of Upper Cambrian Mt. Simon Formation deposited on the mid-continent region of North America during the Dreisbachian transgression. The Mount Simon Formation is a fine to coarsegrained, moderately to well sorted, quartz arenite with a local basal conglomerate. The Mount Simon Formation varies in thickness 40 to 180 meters in the Upper Mississippi Valley. Locally, in the Chippewa Valley area, the lower part of the Photo 3 - Cross-bedded conglomerate and sandstone of the Cambrian Mount Simon Formation in the Irvine Park area, Chippewa Falls. Photo courtesy of Scott Clark (UW-Eau Claire). 9 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 7 – Conceptual field sketch of the unconformity at Irvine Park. Figure from Chan et al. (1991). Stop 2 – Penokean and Mid-Continent Rift Intrusions at Lake Wissota Dam grain size distribution shows a generally fining upward sequence. Precambrian Intrusion Lat: 44.9429° Long: -91.3425° The Paleoproterozoic biotite tonalite (trondhjemite) showing spheroidal and saprolitic weathering at this location is interpreted to be similar to the larger trondhjemite intrusion that underlies much of the Chippewa River valley. The trondhjemite can be more easily observed below the Chippewa Falls hydroelectric dam in downtown Chippewa Falls and below the Wissota hydroelectric dam (Stop 2 in this guidebook). The biotite trondhjemite at Chippewa Falls Hydro was dated by Van Schmus (1980) at 1,840 ± 15 Ma. Saprolites like the one exposed here are characteristic of areas of prolonged tropical to subtropical weathering on a granitoid bedrock surface of low relief. The saprolite at this outcrop contains high clay content and angular quartz and feldspar. The alteration intensity increases approaching the Cambrian Mt Simon Formation. This outcrop is located on the downstream side the dam on Lake Wissota. Drive to the end of 74th Avenue in Chippewa Falls and park in the Chippewa Rod and Gun Club & Marina. From here, you can walk southward along the access road to the dam (about 1 km). There are several places to cross the small steam to access the largest part of the outcrop. The largest potential hazard at this location is the stream crossing and uneven, wet walking area. A ladder or other temporary structure might be required to assist in crossing the stream if water levels are high. This outcrop highlights some of the magmatic history in this region. The majority of the exposure here is a Paleoproterozoic biotite tonalite (trondhjemite) that has local pods and dikes or medium gray biotite tonalite and alkali feldspar granite pegmatite. The outcrop is intruded by at least three gabbroic dykes associated with the mid-continent rift. The largest 10 �Proceedings of the 69th ILSG Annual Meeting - Part 2 of which is clearly visible in arial view (Figure 8). The entire area is covered by thin outwash gravels and silts that varies with seasonal flooding events. Some of the tonalite near the Chippewa River displays the same spheroidal weathering seen at Irvine Park so this location is just below the Great Unconformity and displays some of the same associated potassic alteration along faults and joints seen in Irvine Park (Stop 1). The potassic alteration is responsible for most of the pink color seen in outcrop. Figure 8 - (top) Generalized geology of the Wissota Dam region. Figure modified from Myers et al. (1980). (bottom) Aerial view of the outcrops with the mid-continent rift highlighted. Image obtained from Google Earth. tonalite for rocks with higher mafic concentrations. The oldest, abundant rock at Wissota Dam is a weakly foliated hornblende, biotite trondhjemite composed of oligoclase (50%), quartz (30%), microcline (5%), biotite (10%), and 5% hornblende with common accessory euhedral to subhedral titanite (Photo 4). Weak foliation strikes Nl5°W and dips steeply east. This is intruded by small dykes and masses of medium-grained, medium-grey hornblendebiotite tonalite (± epidote) that locally contains Granitoid Intrusive Suite Most of the Paleoproterozoic intrusive igneous rocks at Wissota are quartz diorites or tonalites with various proportions of hornblende and biotite. For clarity, and to be consistent with the terminology used by previous geologists working in the Chippewa River Valley, on this field trip we refer to the lightest colored tonalites (color index 15 or less) as trondhjemite and reserve 11 �Proceedings of the 69th ILSG Annual Meeting - Part 2 trondhjemite is an FI-type felsic rock with strongly depleted HREE (Figure 5) representing deep crustal melting (Hart et al. 2004). The trondhjemite is cut by east-northeast-trending pegmatite veins and pods and quartz ± pyrite) and epidote veinlets. Potassic alteration especially along any fractured surfaces the trondhjemites produces a pink color in outcrop (Photo 5). Minor cataclastic fault zones cut the granitoid intrusions with leftlateral displacement. A thin, branching discordant sheet of foliated biotite trondhjemite approximately 1-3 meters wide and trends N55°W. Drag folded foliation in the enclosing rocks indicates left-lateral displacement. Photo 4 – Photographs of main lighter colored tonalite phase at Wissota Dam. (A) Photomicrographs in plane-polarized light showing feldspar grains are lightly weathered with opaque rims around titanite. In cross-polarized light, quartz grains show moderate undulatory extinction. Photo from Klier (2019). B) Field photograph of biotite tonalite (trondhjemite) showing medium-grained, equigranular texture. Feldspars weather pink in color and mafic phases tend to be recessively weathered. lenticular xenoliths of banded amphibolite. The tonalite pods show no grain size diminution and sometimes have irregular shapes suggesting that some tonalites may be enclaves of earlier phases of the trondhjemite. In other cases, the tonalites are clearly dykes crosscutting the trondhjemite. The tonalite dikes tend to be unaltered with vitreous dark-brown biotite (~25%) and lack foliation. All minerals in the foliated tronhjemite show internal fracturing and dislocation, and contain quartz grains with undulatory extinction, display grain boundary migration and dynamic quartz recrystallization (Klier, 2019). The Photo 5 – Photographs of pegmatite and associated alteration at Wissota Dam. (A) Thin quartz-epidote veining and potassic alteration surrounding conjugate fracture sets adjacent to pegmatite. (B) Coarse grained texture of the pegmatite. Feldspar crystals can be as large as 5-7 cm in size. 12 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Slickenside fault surfaces elsewhere in this outcrop have similar strike and dip with the slickensides plunging 5°NW. of the largest dyke and the mineral chemistry was examined using SEM-EDS and optical petrography. The main dyke has an aphanitic chilled margin a few cm wide along both the north and south sides and the grain size consistently coarsens toward the middle of the dike into a medium grained olivine gabbro (Photo 7A). A prominent set of joints perpendicular to the cooling surface along the dike walls are interpreted as columnar joints and these are especially prominent on the south side below the power lines. More pronounced columnar joints are also seen in one of the smaller (2m wide) dikes along the northwest side of the area next to the Chippewa River. No internal contacts are apparent at the outcrop scale suggesting that this large dike represents a single cooling unit of magma intruded into the upper crust. West of the power lines the dike is cut by two faults, one left lateral strike slip fault with a few meters of displacement and a low angle reverse fault with well-developed chlorite slickensides and extensive alteration including chlorite and hematite, and calcite filled tension fractures. Mid-Continent Rift Dykes Three diabase dykes related to mid-continent rift extension intrude the granitoids (Photo 6) exposed below the Wissota Dam spillway and the largest dike is an ENE trending (~N65E) olivine tholeiite that averages 47m in width. The large dyke has a notable sharp and chilled margin. Unpublished data from the dyke at this location and others along the Chippewa River indicate a tholeiitic composition that shows slightly more Mg-enrichment trends on AFM diagrams in comparison to other parts of the dyke swarm in the region. Ongoing student-faculty research at the University of Wisconsin-Eau Claire is examining the composition of the large dyke at Wissota Dam. Samples were collected as a cross section The chilled margins consist of very finegrained plagioclase with variable compositions ranging from An35 to An63, in a devitrified-glass matrix crowded with submicron Fe-Ti oxides and sparse sub-calcic augite (Average cpx = [Mg.68Fe.60Ca.55Al.09Ti.02Mn.01] [Si1.91Al.09O6]). Within two meters of the north side of the diabase the dike contains single crystals of labradorite up to 10 cm across apparently sourced from a deeper magma chamber and transported (floated?) upwards during intrusion of the dike. Locally the chilled margin is altered to chlorite and very fine grained bright blue-green celadonite (Photo 7D), alkali-feldspar and dark red biotite. Five samples collected from the central 35 m of the dike all consists of an olivine gabbro with a well-developed ophitic texture (Photo 7B). The mineralogy from the center includes both titaniferous augite (1-2wt% TiO2) and titanaugite (>2wt% TiO2) oikocrysts with pink and lavender Photo 6 – Photographs showing sharp, chilled margin of mid-continent rift gabbro with Paleoproterozoic trondhjemite intrusion. 13 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Photo 7 – Photographs of mid-continent rift gabbroic dyke at Wissota Dam. (A) Outcrop photo showing fractured and weathered surface of dyke. Weathered surface shows medium-grained texture. (B) photomicrograph in crosspolarized light (40x) showing ophitic texture. (C) Photomicrograph in plane-polarized light (40x) showing aggregate of euhedral to subhedral olivine (ol) crystals (Fo 40-45) in plagioclase and cpx matrix where cpx as pinkish purple pleochroism typical of the titanaugite composition. (D) Photomicrograph in plane-polarized light (100x) showing greenish blue celadonite (cel) replacing biotite (bt) in the transitition zone between the chilled margin and dikes central olivine gabbro. pleochroism, laths of normally zoned plagioclase with labradorite cores (An55-65) and thin rims of andesine (An30-35) and unusually large aggregates of euhedral to subhedral olivine containing over 50 individual olivine crystals (Photo 7C). The augite and biotite show little variation across the dyke but the olivine becomes progressively more Fe-rich towards the south with an average of Fo43 in the north to Fo35 near the southern contact. The opaque minerals are primarily ilmenite with titaniferous magnetite lamellae often rimmed with a highly titaniferous reddish orange biotite. In the transition zone between the chilled margin and the center 30 m of the dyke much of the biotite is replaced (altered) with celadonite K(Mg,Fe2+)(Al,Fe3+)[Si4O10](OH)2 with a brilliant blue-green color in plane polarized light (Photo 7D). Unusual olivine aggregates (glomerocrysts?) occur throughout the central 35m of the dyke and often consist of more than 50 crystals (Photo 8). In some of the olivine aggregates the minerals show at least some crystallographic alignment. Olivine within individual aggregates have a very narrow range of chemistry. In one aggregate 16 grains were analyzed and the average composition was Fo47.5±0.2(2σ); this standard deviation is about the 14 �Proceedings of the 69th ILSG Annual Meeting - Part 2 magma with limited chemical variation and could be produced by turbulent flow (synneusis) agglomeration or by a high degree of undercooling and ripening of dendritic olivine. It seems very likely that this dike was an active conduit for magmas reaching the surface to produce MCR lava flows even though Chippewa Falls is almost 200 km south of the main MCR rift axis. Geochemical results which are pending should help further constrain the system. Stop 3 – Gneisses and Pegmatites at Jim Falls Photo 8 – Photomicrograph in cross-polarized light of olivine aggregate (glomerocrysts) showing consistent orientation of olivine crystals in the cluster. Gray crystals all have an optic axis almost perpendicular to the section. Magnification 100X. Lat: 45.0549° Long: -91.2734° same size as the analytical error for EDS analysis on olivine. Olivine aggregates have been described from several basaltic conduits where they have been attributed to differential crystal movement during turbulent flow in an active conduit such as at Kilauea (Helz, 1987) or as xenocrysts extracted from a deforming cumulate. However, there is no reference to aggregates with such a large number of crystals. The texture and chemistry of the aggregates at Wissota come closest to matching olivine aggregates collected from lava flows at La Reunion (Welsch et al., 2013) which they ascribe to rapid dendritic crystal growth and ripening under a high degree of undercooling (-ΔT > 60°C) from low viscosity basalts. Petrographic Interpretation: The dyke is sourced from a lower-level fractionated magma chamber of enriched basalt (E-MORB or alkali olivine parent) as evidenced by the olivine composition (~Fo40), plagioclase (An60) and titanaugite/ilmentite modal mineralogy. Plagioclase zoning from An60 cores to An30 rims suggests at least limited reaction with wall rocks. As a fractionated magma it seems likely that the ascending magma contained phenocrysts of both olivine and plagioclase that were kinetically fractionated by turbulent flow resulting in a chilled margin largely devoid of phenocrysts. The olivine aggregates form in equilibrium with This outcrop is located within the spillway of the hydroelectric dam near the community of Jim Falls. About 500 m north from the intersection of 15 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Highway 178 and County Highway Y (the main road into the community of Jim Falls), there will be an old, abandoned bridge that that used to be the access bridge to the community. There is ample parking in front of this bridge. On the south side of the old bridge is a small foot path that leads down to the outcrops along the river. These outcrops are smoothly polished from the flooding at the dam. They are uneven and quite slippery when wet. If water levels are high, there are also outcrops immediately downstream of the spillway to the north. This location has intensely folded amphibolite and biotite quartzofeldspathic gneiss that is intruded by granitoid intrusions and associated pegmatites (Figure 9). Intense shearing and metamorphism results in little preserved primary texture within the gneisses and amphibolites. On the east bank of the river is a gabbroic dyke associated with the mid-continent rift. Figure 10 - Tera-Wasserburg concordia diagram of biotite quartzofeldspathic gneiss from Jim Falls. A wide spread of ages is suggestive of a detrital origin. Figure from Klier (2019). sedimentary rocks. Trace element geochemistry from Klier (2019) was inconclusive in determining volcanic protolith because of low Ti abundance. Preliminary petrography from student projects at the University of Wisconsin-Eau Claire and Kleir (2019) seem to suggest that amphibolites are rather rare. Other geochemical results from ongoing research at the University of Wisconsin-Eau Claire are pending. The outcrops at this stop are one of the original “Archean” exposures of the Marshfield terrane that was described in in Sims et al. (1989), but new data in the region casts doubt on that original interpretation. The gneisses at this location were assigned a U/Pb age of 2522 ± 22 by Sims et al. (1989). Little description of the data was provided in that original reference and the date itself was referenced as unpublished data from personal communication. Klier (2019) resampled the gneiss from the region and analyzed zircons using LA-ICPMS. The resulting data clearly shows a large spread of ages and a significant portion of those are Paleoproterozic in age. There are clearly older sources of detritus for these meta-sedimentary rocks, some as old as 2841 Ma. However, the dominant source of detritus was Paleoproterozoic (Figure 10). Based on this new data, the Jim Falls region is not obviously an Archean crustal fragment. A biotite quartzofeldspathic gneiss was sampled by Klier (2019) for U/Pb geochronology. Based on recent field work, this rock appears to be the dominate lithology that exists in the immediate region around and under the bridge. Kleir (2019) describes the rock containing classic mylonitic textures and is comprised of quartz (60%), alkali feldspar (25%), biotite (15%), and trace zircon (Photo 9A). There are prominent bands of porphryoblastic quartz and cryptocrystalline biotite. Biotite is also present rarely as larger “destroyed” grains. Quartz has undulatory extinction and has undergone grain boundary migration recrystallization. Some feldspar grains display domino-type fragmented porphyroclastic textures. Portions of feldspar grains have diminished to sericite. Weakly Amphibolites and Gneisses Myers et al. (1980) interpreted the amphibolites and gneisses in this region to be derived from mafic volcanic rocks and associated 16 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 9 – Precambrian geologic map of Chippewa River near Jim Falls. Figure digitized from Myers et al. (1980). 17 �Proceedings of the 69th ILSG Annual Meeting - Part 2 isoclinally folded amphibolite occur in the granitic rocks. Granitoids and Pegmatites Granitic rocks range in composition from trondhjemite to alkali feldspar granite. Pegmatite dike intrusion occurred at several stages of "granite" intrusion. Mineralogy includes alkali feldspar (65%) quartz (32%), plagioclase (3%), and trace zircon.. The grains are subhedral to anhedral with intergrowths and granophyric textures occasionally present. Quartz grains appear stretched and strained and have undergone either subgrain rotation recrystallization or grain boundary migration recrystallization (Klier, 2019). The older granitic rocks are foliated and locally mylonitized. Shearing and boudinage of pegmatite stringers transposed them into oblique concordance with lamination in the enclosing rocks. A rough correlation can be made between relative age and concordance of veinlets. thinly laminated amphibolite was intruded by granite so that lenticular slices of the amphibolite were dragged en echelon away from the wall (Photo 10). The coarse granite pegmatite intruded under stress contains en echelon fractures filled with very coarse quartz. Photo 9 – (A) Photomicrograph in plane-polarized light of biotite quartzofeldspathic gneiss showing sericite-altered feldspar crystals and pronounced dynamic recrystallization of matrix. Foliation defined by elongation of grains and alignment of biotoite. Photo from Klier (2019). (B) Outcrop photo showing gneiss intruded by boudinaged granitic dykes. Gneissic layering is very fine and difficult to see in this photo. chlortizied biotite bands define foliation (Photo 9A). Garnetiferous hornblende gneiss and schist are folded with high-amplitude isoclinal folds with a persistent ENE strike. Small (F2) folds plunge gently east-northeast. These are folded F1 isoclinal folds, and a few hinges can be found in the outcrop. Some of the granitic pegmatites appear to be folded as well or are slightly boudinaged (Photo 9B), suggesting that pegmatites intruded prior to F2 or where exploiting layering within the folded gneisses and amphibolites during emplacement. Xenoliths of Photo 10 – Typical intrusive relationship between pegmatite surrounding amphibolites and gneisses. Small pegmatite veinlets and en echelon fracturing along margins is common resulting in lens-shaped gneissic fragments. 18 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Stop #4 – Amphibolites and Gneisses at Cornell Dam outcrops almost continuously for 4 km down the river. The amphibolite could also be classed as a gneissic, mafic hornblende tonalite or hornblende gneiss. This is also one of the few areas that this trip visits that you can potentially see primary depositional features! Immediately below the dam, the rock is a fine-grained amphibolite with elongate bulbous inclusions that appear to stretched pillows (Photo 11A) that contain local irregular to lens-shaped quartz-epidote nodules (Photo 11B). Lat: 45.1625° Long: -91.1596° The amphibolite is composed of subhedral to anhedral, lensoidal hornblende clusters (54%) with coarse, lensoidal porphyroclasts of twinned plagioclase (28%) and fine-grained quartz. Banding in the amphibolite Is cut by lenticular segments of granite and quartz veinlets. Garnets This outcrop is located within the spillway of the hydroelectric dam near the community of Cornell. About 500 m southwest from the bridge into Cornell on Highway 178 is the Wisconsin Department of Natural Resources Ranger Station where there is ample parking. Just south of the Ranger Station is a small road (called Pine Point Road) that leads toward the water. There are foot trails and gated roads (accessible by foot) that lead toward the outcrops at the dam and by the river. These outcrops are uneven but are generally dry and easily traversed under normal river conditions. If water levels are high, outcrops can also be visited on the shoreline above the dam near the Municipal Works buildings in Cornell. Photo 11 – Flow-like features in the amphibolites at Cornell Dam. (A). Streched pillow-like structures with cm-scale darkened pillow margins. (B) Irregular quartz-epidote nodules that are common in submarine or hydrothermally-altered submarine flows. Myers et al (1980) described this location as a laminated (foliated) garnet amphibolite that 19 �Proceedings of the 69th ILSG Annual Meeting - Part 2 in the amphibolite tend to be moderately poikioblastic with minor rotational features. The distribution of garnet clusters shows little relation to banding. Trace element chemistry of these rocks show clear tholeiitic trends and flat REE patterns on normalized diagrams (Figure 5). Further downstream from the dam, the rock becomes notably lighter in color and there appears to be a lower percentage of amphiboles. These rocks share similar trace element patterns (Figure 5) and are interpreted to be genetically related. The reason for the change in texture may be due to increase structural modification and gneissic banding development. The outcrops are also intruded by mafic dykes that clearly cross-cut the dominant foliation (Photo 12). These dykes trend N40°W and are approximately 30-50 cm in apparent thickness with no obvious chill margin. Since these dykes cross-cut the structural fabric, they are assumed to be related to the mid-continent rift. However, no petrography or chemistry has been done to confirm this hypothesis. of the river, there is a small vehicle parking area and footpath that leads to the dam on 260th Avenue about 100 m west of the intersection with County Highway M. This trail will take you to the dam and carefully navigate to the north bank of the river downstream of the dam. To access the south bank of the river, drive to the end of Irvine Avenue before it turns into a private driveway. There are numerous small foot paths that will lead to the south bank of the river. Photo 12 – Gabbroic dyke intruding through amphibolites at Cornell Dam. Stop 5 – Amphibolites and Deformed Diorite at Holcombe Dam The outcrops at this location are considered part of the Pembine-Wausau terrane, or is it? While the location of the Eau Pleine Shear Zone becomes problematic in this region, Sims et al. (1989) consider the Jump River Shear Zone the northern boundary of the Marshfield Terrane. Magnetic lineaments mark this shear zone and extend it close to these outcrops. Depending on Lat: 45.2251° Long: -91.1289° As time permits, each side of the river at Holcombe Dam has different rock types to examine, but are vastly different approaches to see them. To visit the outcrops on the north bank 20 �Proceedings of the 69th ILSG Annual Meeting - Part 2 the map, the shear zone lies just north or just south of the outcrops at this location (e.g. Mudrey et al., 1987). The rocks at this stop are a gneissic quartz diorite intrusion and an amphibolite schist (Figure 11). So, Marshfield or Pembine-Wausau terrane? The newest geochronology from the region is inconclusive. The rock exposed on the southern bank of the river below the dam is a foliated amphibolebiotite schist (Photo 13). Klier (2019) describes this rock as banded at the microscopic scale. Quartz grains are well banded, fairly subhedral to anhedral and feature undulatory extinction. Their boundaries are somewhat irregular and indicative of bulging recrystallization. Amphibole grains are hornblende to tremolite. Biotite appears as brown to light green grains and typically feature Photo 13 – Photomicrograph in plane-polarized light of amphibole-biotite schist with trace amounts of epidote in a quartzofeldspathic matrix. Figure from Klier (2019). Figure 11 – Precambrian geologic map of the Holcombe Dam region. Unit Abbreviations: qd: quartz-diorite, bgn: banded gneiss, ams: amphibolite schist. Figure from Myers et al. (1980). 21 �Proceedings of the 69th ILSG Annual Meeting - Part 2 shear bands with cryptocrystalline biotite crosscutting crystals. Klier (2019) obtained a U/Pb zircon age via LA-ICPMS of 1858 ± 1.0 Ma (Figure 12). This age does not definitively put the rocks in this region in Marshfield or PembineWausau terrane. There does not appear to be any Archean inherited zircons, as one might expect if Penokean magmas were overprinting an Archean crustal block. Photo 14 – Outcrop of quartz diorite on north bank of Chippewa River at Holcombe Dam. quartz, with minor amounts of biotite, muscovite and epidote. The quartz diorite contains two types of inclusions: hornblende rich ultramafic inclusions and spotted mafic inclusions. Ultramafic inclusions occur along the northwest portion of the exposed quartz diorite, generally less than 0.5 meters in length, although one is at least 2 meters long. Ultramafic inclusions are composed of 7585% hornblende and 11—13% biotite with a small amount of plagioclase (meta pyroxenites?). Chlorite occurs as an alteration product of biotite and less commonly of hornblende and can compose more than 20% of the rock. Figure 12 – Tera-Wasserburg concordia diagram of amphibolitic schist on the south bank of the Chippewa River near Holcombe dam. Figure from Klier (2019). Stop 6 – Tonalites and quartz diorites at Cadott Bridge On the north bank of the river, the outcrop is predominately a synkinematic quartz diorite (Photo 14; Figure 13). The quartz diorite is a medium-grained, dark to medium grey rock with rusty weathering surfaces. It is faintly foliated and has white discontinuous bands and lenticles which are more quartz rich than the rest of the rock. Quartz diorite is composed of plagioclase (32-51%), quartz (11-31%) and mafic minerals (12-33%). Mafic minerals range from entirely hornblende to entirely biotite. The quartz diorite is cut by medium-grained granite pods with migmatitic contacts and by finer-grained dykes with sharp contacts. The granite is a pink, faintly foliated rock which locally contains porphyritic microcline grains reaching 1 cm in size. Granitic rocks consist of plagioclase, microcline and Lat: 45.9535° Long: -91.1508° This outcrop shows is easily accessible under the Main Street bridge in Cadott. Just north of the bridge near the Main Street-Yellow Street intersection there is a parking area on the north bank of the river. From this parking area, there are footpaths that lead to the waters edge. The predominant rock type here is foliated biotite quartz diorite to biotite tonalite (Figure 14) composed of plagioclase (An25-35, 30-55%), quartz (10-40%), hornblende (0-25%) and biotite (0-15%) (Myers et al. 1980). Mafic minerals are partly replaced by chlorite (of several varieties), epidote, and sericite. Magnetite (1-5%) is a by- 22 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 13 – Detailed outcrop map of the quartz diorite gneiss on the north bank of the Chippewa River at Holcombe Dam. Figure from Myers et al. (1980). Figure 14 – Precambrian geologic map of the region downstream of Cornell Dam. Figure modified from Myers et al. (1980). 23 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Photo 15 – Mylonitized biotite tonalite at the Cadott Bridge on the Yellow River. Photo 16 – Photograph of elongated xenoliths (?) of chlorite-rich metavolcanic rocks in biotite tonalite at Cadott Bridge on the Yellow River. product in the chloritization of hornblende. The tonalites have been mylonitized (Photo 15) and locally recrystallized and contain lenticular xenoliths of chlorite and epidote-rich metavolcanic(?) rock (Photo 16). The older cataclastic foliation is axial-planar to isoclinally folded pegmatite, aplite, and quartz layers. These rocks are cut by a pervasive N65-75°W trending foliation and mylonitic shear zones. Acknowledgements Despite decades of regular visits from groups from the University of Wisconsin-Eau Claire, the most extensive detailed maps and rock descriptions were provided by Paul Myers and collaborators in the 1980 ILSG guidebook (Myers et al, 1980). There is some recent research activity in the region, but between new but pending analyses and future ambitions, the descriptions and maps provided in that ILSG guidebook are the most detailed and accurate for the region. A lot of the geologic descriptions have been updated and figures have been digitized while adding new data and insights where available. West of the Yellow River bridge, foliated biotite tonalite encloses angular xenoliths of hornblende tonalite or amphibolite containing strongly deformed aplite and pegmatite stringers. Isoclinally folded quartz, aplite, and pegmatite veinlets exist as angular xenoliths in a lighter biotite tonalite. 24 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Hafften, D., and Radwany, M., 2018, Geothermobarometry of a Precambrian amphibolite from Cornell WI: Proceedings of the Institute on Lake Superior Geology 64th Annual Meeting, Iron Moutain, Michigan, p. 45-46. In addition, the authors of this guidebook would like to thank the countless undergraduate and graduate students that have worked on these outcrops and have continued to inspire new work in the region. Specific acknowledgement is deserving to Matt Leahy and his efforts in digitizing figures and compiling geochemistry for the guidebook. Hannack, G., and Radwany, M., 2018, HornblendePlagioclase thermometry of the Eau Claire River Complex, western Wisconsin: Proceedings of the Institute on Lake Superior Geology 64th Annual Meeting, Iron Mountain, Michigan, p. 47-48. References Aleinikoff, J.N., Walter, M., Kunk, M.J., and Hearn, P.P., Jr., 1993, Do ages of authigenic K-feldspar date the formation of Mississippi Valley–type PbZn deposits, central and southeastern United States? Pb isotope evidence: Geology, v. 21, p. 73– 76. Hart, T. R., Gibson, H. L., and Lesher, C. M., 2004, Trace element geochemistry and petrogenesis of felsic volcanic rocks associated with volcanogenic massive Cu-Zn-Pb sulfide deposits: Economic Geology, v. 99, p. 1003-1013. Helz, R. T. 1987, Diverse olivine types in the lava of the 1959 eruption of Kilauea Volcano and their bearing on eruption dynamics. USGS Professional Paper 1350, p. 691-722. Brown, B. A., 1988, Bedrock geology of Wisconsin, west-central sheet, Wisconsin Geological and Natural History Survey Map 87–11b. Chan, L. S., Myers, P. E., and Hay, R. L., 1991, Features and significance of the PrecambrianCambrian contact in western Wisconsin. Institute of Lake Superior Geology 37th Annual Meeting, Eau Claire, Wisconsin, Field Trip Guidebook 2, 17 p. Klier, J. J., 2019, The Marshfield Terrane: Redefinition of origin through zircon geochronology and geochemistry: Unpub. M.S. thesis, Ball State University, 115 p. LaBerge, G. L., 1996, Volcanogenic massive sulfide deposits of northern Wisconsin: A commemorative volume, Proceedings of the 42nd Annual Meeting of the Institute on Lake Superior Geology, Cable, Wisconsin. DeMatties, T. A., 1989, A proposed geologic framework for massive sulfide deposits in the Wisconsin Penokean volcanic belt: Economic Geology, v. 84, p. 946-952. LaBerge, G. L., and Myers, P. E., 1984, Two early Proterozoic successions in central Wisconsin and their tectonic significance: Geological Society of America Bulletin, v. 95, p. 246-253. DeMatties, T. A., 1994, Early Proterozoic volcanogenic massive sulfide deposits in Wisconsin: An overview: Economic Geology, v. 89, p. 1122-1151. Lui, J., 1997, K-Metasomatism in Uppermost Precambrian Rocks in West-Central, Wisconsin and Southeastern, Missouri. Unpub. PhD thesis, University of Illinois. 227p. DeMatties, T. A., 2018, Effects of paleoweathering and supergene activity on volcanogenic massive sulfide (VMS) mineralization in the Penokean Volcanic Belt, northern Wisconsin, Michigan and east-central Minnesota, USA: Implications for future exploration: Ore Geology Reviews, v. 95, p. 216-237. Lui, J. Hay, R. L., Deino, A. and Kyser, T. K., 2003, Age and origin of authigenic K-feldspar in uppermost Precambrian rocks in the North American Midcontinent. Geological Society of America Bulletin, v. 115, p. 422-433. DeMatties, T. A., 2022, Exploration-resource assessment of productive felsic volcanic centers in the Paleoproterozoic Penokean Volcanic Belt of northern Wisconsin, Michigan and east-central Minnesota, USA: Ore Geology Reviews, v. 141, article 104489. Myers, P. E., Cummings, M. L., and Wurdinger, S. R., 1980, Precambrian geology of the Chippewa Valley, Wisconsin, Institute of Lake Superior Geology 26th Annual Meeting, Eau Claire, Wisconsin, Field Trip Guidebook 1, 123 p. 25 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Mudrey, M. G., LaBerge, G. L., Myers, P. E., and Cordua, W. S., 1987, Bedrock geology of Wisconsin, northwest sheet, Wisconsin Geological and Natural History Survey Map 88-7. Quigley, A., 2016, Setting of the volcanogenic massive sulfide deposits in the Penokean Volcanic belt, Great Lakes region, USA: Unpub. M.S. thesis, Colorado School of Mines, 95 p. Schulz, K. J., and Cannon, W. F., 2007, The Penokean orogeny in the Lake Superior region: Precambrian Research, v. 157, p. 4-25. Sims, P. K., Van Schmus, W. R., Schulz, K. J., and Peterman, Z. E., 1989, Tectonostratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: Canadian Journal of Earth Sciences, v. 26, p. 21452158. Van Schmus, W. R., 1980, Chronology of igneous rocks associated with the Penokean orogeny in Wisconsin: Geological Society of America Special Paper, v. 182, p. 159-168. Van Wyck, N., and Johnson, C. M., 1997, Common Lead, Sm-Nd, and U-Pb constraints on petrogenesis, crustal architecture, and tectonic setting of the Penokean orogeny (Paleoproterozoic) in Wisconsin: Geological Society of America Bulletin, v. 109, p. 799-808. Weber, E. M., and Lodge, R. W. D., 2022, New U/Pb Geochronology from the Proterozoic Penokean Orogen, Wisconsin: Implications for VMS Metallogeny: Society of Economic Geologists Annual Meeting, Denver, CO, paper P5.10. Welsch, B., Faure, F., Famin, V., Barronet, A., Bachelery, P., 2013, Dendritic Crystallization: A Single Process for all of the Textures of Olivine in Basalts?, Journal of Petrology, v.543, p. 539-574. Zi, J-W., Sheppard, S., Muhling, J. R., and Rasmussen, B., 2021, Refining the Paleoproterozoic tectonothermal history of the Penokean Orogen: New U/Pb age constraints from the PembineWausau terrane, Wisconsin, USA: Geological Society of America Bulletin, v. 134, p. 776-790. 26 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Field Trip 2 – Wisconsin’s Paleozoic stratigraphy and tour of Crystal Cave Carsyn Ames, Esther Stewart, William “Bill” Batten, Eric Stewart, Ian Orland Wisconsin Geological and Natural History Survey, University of Wisconsin- Madison, 3817 Mineral Point Rd. Madison, WI 53705 Introduction The Cambrian-Ordovician strata exposed in western Wisconsin were deposited during the major Sauk and Tippecanoe marine transgressions onto the interior of the Laurentian continent (Sloss, 1963). These rocks compose the regional aquifer system, host disseminated sulfide mineralization that contribute to groundwater contamination, and are locally mined as proppant for fracking in the oil and gas industry. Additionally, variable hardness of these units in part controls the formation of ledges and hillslopes in the fluvially-dissected Driftless Area of southwestern Wisconsin. During this field trip, we will focus on Cambrian and lower Ordovician strata of the Sauk sequence (Figures 1 and 2). We start our day touring Crystal Cave, a cave system developed along joints within the Ordovician Prairie du Chien Group dolostone. For the rest of the day, we will visit outcrop exposures of the Cambrian Jordan Formation, Tunnel City Group, and Wonewoc Formation sandstones, and if time permits- the Eau Claire and Mount Simon Formations. We hope this field trip will provide an opportunity to discuss similarities and differences between units deposited on the western side of the Wisconsin Arch and those deposited on the eastern side, where field trip authors have focused much of their work. Additionally, we welcome and encourage discussion between participants that have knowledge of or experience working with these stratigraphic units. Figure 1. Correlation of map units showing relative ages of Cambrian-Ordovician units. COpg: Parfreys Glen Formation, Ce: Elk Mound Group, Ctl: Lone Rock Formation of the Tunnel City Group, Ctm: Mazomanie Formation of the Tunnel City Group, Ctc: Tunnel City Group, Ct: Trempealeau Group, Opc: Prairie du Chien Group including the Oneota and Shakopee Formations, Oa: Ancell Group, including the St. Peter and Glenwood Formations, Osp: Sinnipee Group, including the Platteville, Decorah, and Galena Formations. From Stewart (in revision). Ages from Gradstein et al. (2020). Cambrian-Ordovician strata in the southern Lake Superior Region were deposited on an essentially flat continental shelf in a shallow epeiric sea well within the Laurentian continent (Figure 3, Runkel et al., 2012, 2020). These strata overlie Precambrian bedrock of variable ages across the Great Unconformity, a surface characterized by locally significant topographic relief and weathering and exposed in outcrops around the Eau Claire area. The regional paleogeography that controlled sediment source to sink was defined by several structural highs, including the Transcontinental Arch, Wisconsin Dome, and Wisconsin Arch, and several basins, including the Hollandale Embayment, Illinois Basin, and Michigan Basin (Figures 3 and 4, A very brief geologic history of the Cambrian-Ordovician strata in Western Wisconsin Regional depositional model and setting 27 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 2. Generalized stratigraphic column of Wisconsin. From: Bedrock Stratigraphic Units in Wisconsin Bedrock Stratigraphic Units in Wisconsin [small] - WGNHS. 28 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 3. From Runkel 2020, Figure 4. This figure illustrates a depositional model developed for southeastern Minnesota. The Cambrian- Ordovician strata in Wisconsin are thought to have been deposited in a similar fashion. Runkel et al., 1998). The field stops we will visit in western Wisconsin lie west of the Wisconsin Arch and straddle the eastern edge of the Transcontinental Arch and the southwest flank of the Wisconsin Dome. These structural highs were periodically subaerially exposed and eroded during deposition of Paleozoic units. dominated Great American Carbonate Bank (Figures 3 and 5; Runkel et al., 2012). Sandy Cambrian sediments of the Mt. Simon, Wonewoc, and Jordan Formations were deposited in shoreface, aeolian, wave-, and tideinfluenced settings within the inner detrital belt. Mixed, fine-grained sandstone, siltstone, shale, and carbonate of the Eau Claire Formation, Trempealeau and Tunnel City Groups were winnowed and trapped within a transitional, relatively deeper water moat that separated the inner detrital belt from the Great American Carbonate Bank (Runkel et al., 2012). Dolomite of the Prairie du Chien Group was deposited in relatively shallow water, subtidal to peritidal settings on this carbonate bank. Interfingering sandstone, shale, and carbonate record marine transgressions and regressions that caused reciprocal expansion and contraction of the facies belts. During sea level rise, the carbonate bank advanced landward as siliciclastic-dominated nearshore environments were drowned. Cambrian-Ordovician siliciclastic and carbonate units were deposited in a nearshore, sandstone-dominated inner detrital belt that passed offshore into a relatively deeper water moat, which in turn transitioned into a carbonate- Figure 4. from Runkel and others 1998, regional map showing locations of the Wisconsin Dome, Wisconsin Arch, Transcontinental Arch and Hollandale Embayment. Other depositional basins are shown on map (Michigan and Illinois Basins), as well as regional extent of Paleozoic units. 29 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 5. from Runkel et. al., 2012 showing the depositional environments that produce interfingering of different Cambrian-Ordovician siliciclastic and carbonate units across the Midwest. Conversely, during sea level fall, sandy nearshore facies of the inner detrital belt expanded seaward, limiting carbonate deposition. Paleozoic sedimentary rocks were gently folded and faulted in the Paleozoic, probably related to far-field effects of continental margin orogenic events. Structures in Wisconsin rarely exceed 200 feet in structural relief. Recent mapping in Wisconsin and Minnesota suggests folds and faults are probably related to reactivation of much older Precambrian structures (Figure 8). Deformation probably occurred in at least two pulses: once during the Ordovician (Mossler, 2006; Steenberg and Retzler, 2016; Stewart E.K., 2021) and at least once later in the Paleozoic (Heyl and others, 1959; Carlson, 1961). The importance of these folds and faults for groundwater studies is a topic of active interest. In northern Illinois, sandstones in the core of the Sandwich Fault zone have an order of magnitude reduction in horizontal hydraulic conductivity compared to the surrounding rocks (Hadley and others, 2020). In eastern Wisconsin, the Beaver Dam anticline is associated with a statistically significant increase in detection of dissolved arsenic in groundwater wells (Stewart E.D. and others, 2021). The Wisconsin Arch and its influence on Cambrian-Ordovician strata Strata deposited in areas east (for example, Dodge, Fond du Lac, and Jefferson Counties, Wisconsin) and west (for example, the outcrops we will visit today) of the Wisconsin Arch (Figure 4) were deposited in different sub-basins and tapped different local sediment source areas. In addition, the Dodge, Fond du Lac, and Jefferson County map areas were situated in more proximal locations on the Wisconsin Arch relative to today’s field stop locations. Therefore, the eastern sections include more pronounced exposure surfaces, condensed, or eroded sections, and typically include thinner and less abundant fine-grained intervals. Figure 6 shows a generalized stratigraphic column for Jefferson County (east of Wisconsin Arch), with accompanying pXRF elemental data. Figure 7 shows a stratigraphic column from Trempealeau County in western Wisconsin, south of this trip’s field stops, and west of the Wisconsin Arch. Regional and county scale mapping The most recent regional map for West-Central Wisconsin was published in 1988 by Bruce Structural observations on the CambrianOrdovician strata in Wisconsin 30 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 6. From Stewart (in revision), Bedrock geology of Jefferson County. Jefferson County is east of the Wisconsin Arch. 31 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 7. Core log, Gamma Ray log, and pXRF logs from the Arcadia core, Trempealeau County. Modified slightly from Zambito et al. (2018). Trempealeau County is west of the Wisconsin Arch. Brown (WGNHS). This map (Figure 9) includes all of the Paleozoic units we will see today, as well as the older Proterozoic and Archean rocks that make up the bedrock to the east of Eau Claire. Many of the stops for this field trip were found using the Cambrian contacts from this map. Field Trip Stops Stop 1: Crystal Cave, Spring Valley, WI (Contributed by Ian Orland, WGNHS) UTM location 4964692.71N) for stop (559180.94E, and includes walking, ducking, and climbing 7 stories. Please exercise caution while inside the cave as surfaces may be uneven. Below is a brief We will be touring the cave with staff from Crystal Cave. The tour is moderately strenuous 32 �Proceedings of the 69th ILSG Annual Meeting - Part 2 synopsis of a recent collaboration between WGNHS and UW-Madison’s Geoscience Department on speleothems from southern Wisconsin: Caves are fascinating natural features, and can preserve geologic records of past environments. Relatively recent advances in the methods and precision of geochemical analyses have established cave formations (speleothems) as important scientific tools for understanding climate changes of the last 500,000 years. A number of groups have studied the geochemistry of speleothems in the Lake Superior region. In Wisconsin, much of this work has happened at Cave of the Mounds in Blue Mounds, WI, just outside of the terminal moraine of the Laurentide Ice Sheet and some 20 miles southwest of Madison. While that cave is not the destination for this field trip, this section is intended to highlight the types of information we can learn from caves like Crystal Cave. Both caves are privately-owned show caves that were opened for tours in the late 1930s/early 1940s. Crystal Cave is situated in Prairie du Chien Group dolomites of the Early Ordovician (~475 Ma), while Cave of the Mounds is in Sinnipee Group dolomites of the Middle Ordovician (~465 Ma). The formation ages of passages in each cave are poorly constrained. Stalagmites and stalactites from Cave of the Mounds, however, have recorded environmental signals for >250,000 years. Cave of the Mounds: permafrost record Researchers from UW-Madison collected the first seven stalagmite samples in 2015 for modern U-Th geochronological analysis at UM-Twin Cities. Initial results prompted further sampling and analyses; Batchelor et al. (2019) reports 141 U-Th dates from 19 cave carbonate (speleothem) samples ranging from 250–2 ka. The temporal distribution of these ages revealed hiatuses of stalagmite growth in the cave during both of the last glacial maxima, demonstrating the presence and duration of permafrost (Figure 10). Notably, Figure 8. Cross-section from Dodge County, eastern flank of the Wisconsin Arch, south-central Wisconsin. Note offset of Precambrian basement and Cambrian Elk Mound Group (Ce) through Ordovician Prairie du Chien Group (Opc) and subtle folding of younger units. From Stewart E.K. (2021). 33 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 9. Bedrock geologic of west-central Wisconsin from Brown, 1988. 34 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 10 (*from Batchelor et al., 2019). Speleothem U‐Th ages at Cave of the Mounds (COM) in context with regional and global paleoclimate records. (a) MIS boundaries (odd numbers=interglacial periods, even numbers=glacial periods). (b) Stacked records of δ18O (‰) from benthic marine foraminifera annotated with MIS substage names (Lisiecki & Raymo, 2005). (c) Summer insolation (21 June at 43°N). (d) Atmospheric CO2 (ppm) and (e) CH4 (ppb) concentrations. (f) U‐Th ages from COM speleothems with associated 2σ uncertainties (this study) and statistically significant growth hiatuses (gray and red vertical bars). (g) Paleo‐permafrost reconstructions based on geomorphic features in Wisconsin, including ice wedge casts and polygons (Clayton et al., 2001). (h) U‐Th dates of speleothems from caves in the Midwestern United States in order of decreasing latitude. References provided in the main text. MIS = Marine Isotope Stage changes in the δ18O signal during a time period when warm periods are recorded in polar ice cores and stronger monsoons are recorded in tropical stalagmites (Figure 11). the 18 ky duration of the growth hiatus at MIS 2 was much longer than the hiatus that overlaps MIS 6 (5 ky), consistent with more extensive continuous permafrost in the region during the last glacial period. A combination of microscopic imaging and analysis showed that the δ18O changes each happened in ~10 years, and comparison to a climate model demonstrated that the δ18O changes likely happened as a result of >10°C warming above the cave. These results speak to how quickly and dramatically those polar Cave of the Mounds: Decadal warming events during the last glacial period Earlier this year, Batchelor et al. (2023) published a record of the oxygen isotope ratios (δ18O) of calcite from a Cave of the Mounds stalagmite that grew during the last glacial period. Their interpretation focused on a number of rapid 35 �Proceedings of the 69th ILSG Annual Meeting - Part 2 warming events were propagated across the Laurentide Ice Sheet, which is important for better understanding the dynamics of rapid climate change. As you enjoy the tour of Crystal Cave, consider what geologic stories might be captured in its Figure 11 (*from Batchelor et al., 2023). Stalagmite CM-5 δ18O record in comparison to other regional δ18O records of the last-glacial period. a, Cave of the Mounds (COM; this study) δ 18O record (black line), with associated U-Th ages (black dots/2SD error). Note the error of our age model ranged from 520 to 2800 years and was on average 730 years. b, A stalagmite δ18O record from Buckeye Creek Cave, WV (red line) showing relatively lowmagnitude δ18O changes during the last glacial period. c, A compilation of Chinese speleothem δ 18O records (orange line), showing high-magnitude δ18O changes, which reflects the sensitivity of the East Asian monsoon system to high-latitude warmings (DO events) during the last glacial period. *Note the scale of the y-axis in panels A-C are the same to allow for one-to-one comparison. d, The North Greenland Ice Sheet Project (NGRIP) δ18O record (blue line), showing the timing of abrupt warming DO Events (labeled #s). 36 �Proceedings of the 69th ILSG Annual Meeting - Part 2 speleothems. If you have ideas or questions, feel free to reach out to Ian Orland (orland@wisc.edu)! Stop 2: Prairie Du Chien Group- Kraemer Quarry Entrance Outcrop- 850th Ave between Lincoln Rd and 870th Ave intersections. UTM location 4966004.74N) for stop (564719.58E, We do not have permission to enter the quarryDo not enter the quarry. There is an outcrop of the Prairie Du Chien Group just outside of the quarry gate that continues down the hill from the quarry entrance. This outcrop appears to be a very sandy portion of the Prairie Du Chien Group, possibly representing the lower most Stockton Hill Member of the Oneota Formation, or an interfingering of the Jordan Sandstone within the basal Prairie Du Chien Group. Figure 12. Massive beds, of sandy, carbonate cemented Prairie Du Chien Group. Just to the right of the quarry entrance are massive, 1-2m thick beds (Figure 12). To the left, and down the hill, the massive beds continue and just below them thinly bedded, lighter color units begin to appear (Figure 13). The portion of the outcrop that continues down the hill also contains what may be the Prairie Du Chien Gp./Jordan Fm. contact in the ditch just below the road grade between the outcrop and the road (Figure 14). While not recognized in the formal bedrock stratigraphic column for Wisconsin, the thinly bedded, lighter color units may also represent the Coon Valley Member of the Oneota Formation, often recognized and mapped in Minnesota (Steenberg, J.R., and Retzler, A.J., 2016). We will depart on 850th Ave. by continuing down the slope. To the left near the toe of the slope, there is a valley floor with a barn and small pasture. Figure 13. Massive beds of Prairie Du Chien GroupStockton Hill Member? Possibly atop thinly bedded interfingerings of Jordan sandstone. Looking across the valley floor, there is an outcrop of Jordan sandstone just across the creek (Figure 15). 37 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 15. View of valley floor, at toe of slope driving down 850th Ave., looking across pasture towards Jordan outcrop just across creek. 18). This outcrop (Figure 17) is likely close to the base of the Figure 14. Arrow pointing to possible Prairie Du Chien Gp/Jordan Fm. contact in ditch just below road grade. Jordan/St. Lawrence contact (labeled in Figure 16), and the floodplain that the Eau Galle River runs through most likely represents the top of the St. Lawrence Formation. Stop 3: Jordan Formation- Cth B and 770th (Spring Lake, Wisconsin) UTM location 4962594.39N) for stop The Jordan Formation of the Trempealeau Group has been highly studied in both Wisconsin and Minnesota (Mudrey, M.G. Jr. ed, 1997 and references therein). The distinction between and regional application of the quartzose and feldspathic sandstones in this formation have also been debated (Runkel 1994 and Byers and Dott, 1995). Overall, the Jordan Formation represents a coarsening upward sequence that is conformable (562605.40E, Lithofacies of the Jordan Formation are described in Runkel, 1994 and are as follows: 1) very fine-grained hummocky cross-stratified and burrowed sandstone, 2) fine-grained, trough cross-stratified and burrowed sandstone, 3) medium- to coarse-grained, large-scale crossstratified sandstone and 4) thinly interbedded sandstone, mudstone and shale. They note that lithofacies 4 may only be relevant to certain areas in Minnesota (Figure 18). Authors are open to discussion as to where this particular outcrop falls in Runkel’s 1994 classification schema (Figure Figure 16. View of the outcrop across Cth B with approximate contacts labeled. 38 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Iron staining Figure 17. A. View of outcrop. Note the cross bedding and iron staining above hammer. B. Possible iron concretions? PDC Jordan Silcrete at its basal contact with the St. Lawrence, and unconformable with the Prairie Du Chien Group contact at its top. The Coon Valley member of the Jordan is not formally recognized in the stratigraphic column of Wisconsin (WGNHS Figure 19. Photo of core from Jefferson County, Wisconsin (east of Wisconsin Arch) modified from Kusick, 2022 M.S. Thesis. This interval of core shows the contact between the Jordan Formation and the Prairie Du Chien Group. 2011), though it has been noted above the Jordan Fm. in southern parts of the state. A recent M.S. dissertation (Kusick, 2022) discussed, in detail, both the stratigraphy and depositional environments of the CambrianOrdovician units east of the Wisconsin Arch. Kusick (2022) describes the Jordan sandstone as being comprised of only 2 facies of cross stratified sandstone and shaly sandstone, and as being deposited in an upper to lower shoreface environment. These authors would also like to note that locally, the Jordan Formation east of the Wisconsin Arch includes silcrete and clay, and hosts disseminated sulfides (Figure 19). Stop 3a: Rock Elm Impact Structure- Rock Elm, WI- lunch at Nugget Lake County Park UTM location 4948450.76N) Figure 18. Figure 2 from Runkel, 1994 illustrating the different lithofacies of the Jordan Sandstone in Minnesota. 39 for stop (561573.58E, �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 20. Core photos showing jumbled and deformed Cambrian strata from the southern edge of the Rock Elm central uplift - from WGNHS archives. No set stop, informational only as we’ll be eating lunch at a park within the crater. detected in detrital zircon grains and is interpreted to be caused by the impact (Cavosie et al., 2015). The field trip will go through the Rock Elm impact structure (Figure 20), located in Pierce County around 35 miles WSW of Eau Claire (Figure 21). The Rock Elm impact structure is the largest deformation event recorded in the Paleozoic section of western Wisconsin. The structure contains a 6.5 km diameter ring boundary fault and a central uplift 1 km across (Cordua, 1985). Where control exists, the ring boundary fault is thought to have accommodated 45 meters of down-in-the-center displacement (French and others, 2004). Much of the interior of the ring boundary fault is filled with the relatively flat-lying Rock Elm shale and the overlying Washington Road sandstone, which have a combined thickness of approximately 48 meters. These units are unique to the area, and do not exist outside of the ring fault. These units are described based on numerous outcrops, many given in Cordua (1987) and Cunningham and others (2011). The central uplift contains outcrops of tilted Mt. Simon Formation (Figure 20), which suggests 250 to 300 meters of uplift within the core zone relative to rocks outside the impact structure (French et al., 2004). Reidite, a high pressure polymorph of zircon, has been Stop 4: Skolithos burrows in Tunnel City Group-330th Ave. between HWY 25 and Cth Y (Private Property!!!) UTM location 4961335.76N) for stop (586184.90E, We will park on a private drive and walk east along the road to this outcrop. This stop in the Tunnel City Group is an excellent example of Skolithos burrows (Figure 22) which are common in the Tunnel City Group. This outcrop is likely the Tomah Member of the Lone Rock Formation. Excellent examples of cross-stratification can be seen at this outcrop as well. 40 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 21. Map plate from the 2007 Wisconsin Geological and Natural History Survey Open File Report on the Rock Elm impact structure (Cordua and Evans, 2007). 41 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 22. Tunnel City Group outcrop with excellent examples of Skolithos burrows and possibly multiple types of cross-stratification. “Tunnel City Group (Cambrian) The Tunnel City Group is comprised of the Lone Rock and Mazomanie Formations. Similar to neighboring La Crosse County (Evans, 2003), the Mazomanie Formation was not recognized in Trempealeau County. Stop 5: St. Lawrence Formation/Tunnel City Group road cut- Cth C and Cth Y UTM location 4958918.89N) for stop (587368.83E, Lone Rock Formation. The Lone Rock Formation (Figure 23) and its members are identifiable in the map area. The members, from oldest to youngest, are Birkmose, Tomah, and Reno; these are not differentiated at the map scale. The Birkmose Member is a dolomitecemented, coarse-grained, glauconitic sandstone to sandy dolostone with flat-pebble conglomerates; the Tomah Member is a tan to white-colored, medium-grained, glauconitic quartz sandstone; and the Reno Member is a glauconitic medium- to coarse-grained quartz sandstone with flat-pebble conglomerates. Palaeophycus and Skolithos are common, as is hummocky cross-stratification and crossstratification bounded by horizontal bedding surfaces. The contact with the overlying St. Lawrence Formation is sharp and unconformable. The road cut is just west of the intersection of Cth C and Cth Y. We will park and walk to this outcrop. Cth C is a fairly busy road, please exercise caution when you decide to cross. Recent mapping in Trempealeau County, southeast of stops 5 and 6, has produced interesting work on both the geological relationships of the Cambrian- Ordovician rocks, and the quality of groundwater in the west-central part of the state. Zambito and others, 2018 published the following unit description for the Tunnel City Group: 42 �Proceedings of the 69th ILSG Annual Meeting - Part 2 phyllosilicate mineral. Another interesting part of this road cut is the bench approximately 35ft up. This bench feature likely represents the unconformable contact Zambito and others, 2018 alluded to with the overlying St. Lawrence Formation. The Mazomanie Formation is generally not observed in this part of the state and is more prevalent in the southern parts of the state where it interfingers the Lone Rock Formation (Mudrey, M.G. Jr. ed, 1997 and references therein). St. Lawrence Fm. above bench Reno Member Tomah Member A 2019 study by Zambito and others investigated the relationship between groundwater quality and the geochemistry of the Tunnel City-Wonewoc units in western Wisconsin. This study notes that sulfide bearing minerals are disseminated between the two units in west-central Wisconsin, and they call for more work to better understand the geochemical effects of oxidation of sulfide minerals during groundwater pumping in this part of the state. Our next stop will be at an outcrop of Wonewoc sandstone, and we will pass other outcrops of this unit on our drive. Figure 23. Road cut showing contacts between the St. Lawrence Fm., and Reno and Tomah Mbrs. of the Lone Rock Fm. This is the view from the north side of Cth C. The Lone Rock Formation is commonly exposed in shale pits, along roads leading to ridgetops, and at the top of sand mine high walls where the Wonewoc Formation is extracted and the Birkmose Member forms the caprock. The formation is approximately 150 feet thick in the map area. Elemental data for part of the Lone Rock Formation is shown in plate 2 [figure 7]. These data show the formation’s lithologic variability, in particular the distinct upper carbonate-cemented and lower sandstone dominated intervals in the Birkmose; the lower interval consists of reworked quartz grains from the underlying Wonewoc with interspersed, rare glauconite grains and phosphatic brachiopods.” These authors find this to be an excellent, and representative description of the unit for the westcentral region. – Zambito and others (2018) Overall, the Tunnel City Group both east and west of the Wisconsin Arch are quite similar. As examined at this stop, west of the Arch, the Tunnel City Gp. East of the Arch is also a quartz sandstone with glauconite and trace amounts of shale. Stop 6: Wonewoc road cut- Cth Y UTM location 4959793.83N) Figure 24 shows a small part of the westernmost portion of the outcrop. The very dark, greenish-black bed just below the more resistant dolomitic bed is rich in the mineral glauconite, which is an iron potassium for stop (593272.27E, The Wonewoc Formation is a fine to coarse sandstone unit with medium to thick beds, highangle trough cross-stratification and some 43 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 24. A. View of westernmost point of the outcrop. B. close up of the phosphatic rich, friable sandstone of the Tomah Member. orange, iron rich bed on the south side of Cth Y that doesn’t seem to appear in the north face of the outcrop. feldspar (Mudrey, M.G. Jr. ed, 1997). Brachiopod fragments, Skolithos burrows (which we observed at stop 4), and Climactichnites are somewhat common in the fossiliferous Ironton Member of this formation. The upward contact (Figure 25) with the Tunnel City Group is gradational and fines upward; the basal contact with the Eau Claire Formation has been debated as to whether it is gradational or not (Mudrey, M.G. Jr. ed, 1997 and Ostrom 1978). Note the In the 1990s, to better characterize aquifer and confining units, the Minnesota Geological Survey began focusing on the hydrostratigraphic characteristics of geologic units (1998 ILSG field guide). Hydrostratigraphic subdivisions include: 1) fine clastic; 2) coarse clastic; 3) carbonate; 4) clastic/carbonate mix. While this approach has not been implemented as part of bedrock mapping in Wisconsin, its importance has been recognized by Wisconsin hydrogeologists in lithologically complex units such as the Eau Claire Formation (Bradbury and Runkel, 2011). The authors are open to questions, and discussion of this method as it may pertain to future groundwater study needs across the Midwest. Additional stops if time permits: Devil’s Punchbowl – Eau Claire Formation: UTM location 4966909.29E) Figure 25. View of the Wonewoc outcrop on Cth Y. 44 for stop (582783.00N, �Proceedings of the 69th ILSG Annual Meeting - Part 2 Park in the parking lot, walk east towards the stairs, and take them down the trail into the Punchbowl. Acknowledgements A special thanks to Eric Stewart and Ian Orland for contributing content to this guide. A very special thanks to Bill Batten for helping scout field locations and always knowing where to find the best contacts. Additionally, this guide would not have been possible with consulting Dave LePain’s mapping notes and field guides from Pierce and St. Croix counties and the work of others who have previously published work on these Paleozoic units. This is a classic stop for field trips in this part of the state. Devil’s Punchbowl is managed by the Landmark Conservancy- please do not use rock hammers on the outcrops and be good stewards of the landscape. This outcrop shows the relationship between the Eau Claire Formation and the Wonewoc Formation. Expect to see a fine-grained sandstone with swaley cross beds in the Eau Claire Formation, and mediumto coarse-grained, cross-stratified sandstone in the Wonewoc Formation at this location (Mudrey, M.G. Jr. ed, 1997). References Batchelor, C. J., Marcott, S. A., Orland, I. J., He, F., and Edwards, R. L., 2023. Decadal warming events extended into central North America during the last glacial period. Nature Geoscience 16: pages 257261, Hwy 37/Hendricks Ave and Silver Springs Dr.- Mt. Simon Formation: UTM location 4958712.01E) for stop (615774.61N, Batchelor C. J., Orland I. J., Marcott S. A., Slaughter R., Edwards R. L., Zhang P., and Li X., 2019. Distinct permafrost conditions across the last two glacial periods in mid-latitude North America. Geophysical Research Letters 46: pages 1331813326, This is a typical Mt. Simon Formation exposure (Figure 26), coarse- to mediumgrained, cross-bedded, iron stained, sandstone, interbedded with shale and fine grained sandstone (Mudrey, M.G. Jr. ed, 1997). Bradbury, K. R., & Runkel, A. C., 2011. Recent advances in the hydrostratigraphy of Paleozoic bedrock in the Midwestern United States. GSA Today, v. 21, pages 10-12. Byers C.W. and Dott R.H. Jr., 1995 Sedimentology and depositional sequences of the Jordan Formation (Upper Cambrian), Northern Mississippi Valley, Journal of Sedimentology, v. B65, no.3, pages 289-305. Cavosie, A. J., Erickson, T. M., & Timms, N. E., 2015. Nanoscale records of ancient shock deformation: Reidite (ZrSiO4) in sandstone at the Ordovician Rock Elm impact crater. Geology, 43(4), pages 315-318. Cordua, W. S. 1985. Rock Elm structure, Pierce county, Wisconsin: a possible cryptoexplosion structure. Geology, 13(5), pages 372-374. Figure 26. View of the Mt. Simon Formation outcrop. This location is heavily iron stained and exhibits excellent examples of sedimentary structures like trough cross stratification and channel forms. Cordua, W. S., 1987. The Rock Elm Disturbance, Pierce County Wisconsin, in Balaban, N. (ed.), Field trip guidebook for the Upper Mississippi 45 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Valley, Minnesota, Iowa and Wisconsin, prepared for the 21st annual meeting of the Geological Society of America North-central section, Minnesota Geological Survey Guidebook Series #15, pages 123-152. Central Section, Geological Society of America, May1-2, 114 pages. Ostrom, M.E.,1978. Stratigraphic relations of Lower Paleozoic rocks of Wisconsin, Wisconsin Geological and Natural History Survey Field Trip Guidebook 3, pages 3-22 Cordua W.S. and Evans T.J., 2007. Geology of the Rock Elm Complex, Pierce County, Wisconsin, Wisconsin Geological and Natural History Survey Open File Report WOFR2007-02, Map, 1 plate. Runkel A.C., 1994. Deposition of the uppermost Cambrian (Croixian) Jordan Sandstone, and the nature of the Cambriand-Ordovician boundary in the Upper Mississippi Valley, Geological Society of America Bulletin, vol. 43: pages 60-71 Cunningham, J., Dolliver, H., and Cordua, W., 2011. Flaming meteors, dark caves and raging water: geological curiosities of western Wisconsin, in Miller, J.D, Hudack, G., Wittkop, C., and McLaughlin, P.I. (eds.), Archean to Anthropocene: Field Guides to the Geology of the Mid-continent of North America, Geological Society of America Guidebook Field guide 24, pages 411-424. Runkel A.C. McKay, R.M., and Palmer, A.R., 1998. High-resolution sequence stratigraphy of lower Paleozoic sheet sandstones in central North America: The role of special conditions of cratonic interiors in development of stratal architecture. GSA Bulletin, v.110 no.2., pages 188-210. doi:10.1130/B26117.1 French, B. M., Cordua, W. S., & Plescia, J. B., 2004. The Rock Elm meteorite impact structure, Wisconsin: Geology and shock-metamorphic effects in quartz. Geological Society of America Bulletin, 116(1-2), 200-218. Runkel, Anthony C., Robert M. McKay, Clinton A. Cowan, James F. Miller, and John F. Taylor, 2012, The Sauk megasequence in the cratonic interior of North America: Interplay between a fully developed inner detrital belt and the central great American carbonate bank, in J. R. Derby, R. D. Fritz, S. A. Longacre, W. A. Morgan, and C. A. Sternbach, eds., The great American carbonate bank: The geology and economic resources of the Cambrian – Ordovician Sauk megasequence of Laurentia: AAPG Memoir 98, p. 1001 – 1011. Carlson, J.E., 1961. Geology of the Montfort and Linden Quadrangles, Wisconsin, in Geology of parts of the Upper Mississippi Valley zinc-lead district: U.S. Geological Survey Bulletin 1123– B, pages 95–138, 2 pls., scale 1:24,000, Gradstein, F.M., Ogg, J.G., Schmitz, M.D. and Ogg, G.M. eds., 2020. Geologic time scale 2020. Elsevier. Runkel, A.C., 2020. Minnesota at a Glance Paleozoic History of Southeastern Minnesota-Ancient Tropical Seas. Minnesota Geological Survey. Retrieved from the University of Minnesota Digital Conservancy, Heyl, A.V., Jr., Agnew, A.F., Lyons, E.J., Behre, C.H., Jr., and Flint, A.E., 1959, The geology of the Upper Mississippi Valley zinc-lead district: U.S. Geological Survey Professional Paper 309, 310 pages., 24 pls. Sloss, L.L., 1963. Sequences in the cratonic interior of North America. Geological Society of America Bulletin, 74(2), pages 93-114. Kusick, A. R., 2022. Stratigraphy, Sedimentology, and Deformational Significance of Cambrian and Early Ordovician Strata Along the Southeast Wisconsin Arch (M.S. dissertation, The University of Wisconsin-Milwaukee). Steenberg, J.R., and Retzler, A.J., 2016. Bedrock geology, plate 2 of Geologic atlas of Washington County: Minnesota Geological Survey County Atlas Series C–39, Part A, scale 1:100,000, Mossler, J.H., 2006, Bedrock Geology of the Prescott quadrangle, Washington and Dakota counties, Minnesota: Minnesota Geological Survey Miscellaneous Map Series M–167, scale 1:24,000, Stewart E.D., Stewart E.K., Bradbury, K.R., Fitzpatrick, W.A., 2021. Correlating Bedrock Folds to Higher Rates of Arsenic Detection in Groundwater, Southeast Wisconsin, USA, Groundwater, v59, no.6, pages 829-838. Mudrey, M.G. Jr. ed, 1997. Guide to field trips in Wisconsin and Adjacent areas of Minnesota. Prepared for the 31st Annual meeting of the North- 46 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Stewart, E.K., 2021. Bedrock geology of Dodge County, Wisconsin: Wisconsin Geological and Natural History Survey Map Series M–508, scale 1:100,000, Stewart (in revision). Bedrock Geologic map of Jefferson County, Wisconsin: WGNHS Map Series, 1 plate, 1:100,000-scale. Wisconsin Geological and Natural History Survey [WGNHS], 2011, Bedrock stratigraphic units in Wisconsin: Wisconsin Geological and Natural History Survey Educational Series 51, 2 p. Zambito J.J IV, Mauel, S. W., Haas, L.D., Batten, W.G., Chase, Streiff, C.M., P.M., Niemisto, E.M., Heyrman, E.J., 2018. Preliminary Bedrock Geology of Southern Trempealeau County, Wisconsin, Wisconsin Geological and Natural History Survey Open File Report WOFR2018-01, 2 plates scale 1:100,000, 27 pages Zambito J.J IV, Haas, L.D., Parsen, M.J., McLaughlin, P.I., 2019. Geochemistry and mineralogy of the Wonewoc-Tunnel City contact interval strata in western Wisconsin, Wisconsin Geological and Natural History Survey Open File Report WOFR2019-01: 28. 47 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Field Trip 3 – Precambrian Geology of the Eau Claire River Valley: Re-discovering the Eau Claire Volcanic Complex Robert W.D. Lodge, Evan M. Weber, Robert L. Hooper Department of Geology & Environmental Science, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54701 of the “prove-it-first” law, or sulfide mining moratorium, in 1997 effectively shut down mineral exploration and mining activities in the region. More recently, the mineral exploration industry has been reinvigorated because of the 2002 discovery of the 18.2 Mt Back Forty deposit in Michigan, easing of the sulfide mining moratorium in 2017, and a recent national push for securing domestic critical mineral resources. However, this has also highlighted the lack of modern datasets on Wisconsin’s mineral deposits that could be used to further our knowledge of the mineral-forming systems in the belt. The Pembine-Wausau Terrane has received most of the historic and recent attention since it hosts approximately 150 million tonnes of known VMS mineralization. However, little attention has been given to the Penokean volcanic deposits that overprinted the Marshfield Terrane that are presented in this guidebook. These volcanic deposits host a VMS prospect (Butler Prospect) and therefore the geodynamic setting of these volcanic rocks clearly are favorable for submarine hydrothermal activity. DeMatties (2022) recognized the gap in knowledge for these Penokean volcanic deposits, known as the Eau Claire Volcanic Complex, within the Marshfield Terrane and their exploration potential. It is a little embarrassing how little we know about the Eau Claire region considering the mineral wealth of the rest of the orogen. Current research at the University of Wisconsin-Eau Claire is aimed at the addressing this issue. Introduction The erosional outliers of Precambrian bedrock in the Eau Claire River valley represent the southernmost extent of the Canadian Shield before it is completely covered by Paleozoic sedimentary strata. The rocks exposed here are part of the Paleoproterozoic Penokean Orogeny, a collisional orogen that resulted from the accretion of the Pembine-Wausau and Marshfield terranes onto the southern margin of the Superior Province. This region was last visited by members of the Institute of Lake Superior Geology in 1980 when a field trip through the region was conducted by Paul Myers and colleagues (Myers et al., 1980) when it was called the “Chippewa Amphibolite Complex”. Since then, the “Eau Claire River Complex” was defined and described in detail by Cummings (1984). There has been ‘new’ U/Pb data collected by the USGS (Sims et al. 1989) and others (Van Wyck et al, 1997; Klier, 2019; Weber and Lodge, 2022), regional syntheses of the Penokean volcanogenic massive sulfide (VMS) mineralization (DeMatties 1989; 1994; 2018; 2022), maps published by government surveys (Brown, 1988), and orogen-wide tectonic model (Shultz and Cannon, 2007) that is being revisited based on new U/Pb data (Zi et al., 2021). The rocks that will be visited on this trip are a critical part of evaluating the tectonic models for the Penokean Orogen and have not been examined using modern analytical techniques. The Penokean Orogen is perhaps best known for hosting numerous VMS deposits. In fact, one of the most complete descriptions of several deposits was published by the Institute of Lake Superior Geology (LeBarge, 1996). The passing The portion of the Eau Claire Volcanic Complex that is visited in this guidebook is not well exposed and its regional context is poorly constrained. Students from the University of 48 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Wisconsin-Eau Claire have been visiting Big Falls and Little Falls locations in this guidebook for decades to learn how to map and describe rocks in the field, measure structures and interpret geologic histories, and learn the basic mechanics of field work. Faculty, students, and alumni from Eau Claire consider these outcrops classic. This guidebook will (re-)introduce these rocks and present some of the ongoing research with the Eau Claire Volcanic Complex. The outcrops visited in this guidebook are accessible by foot, but many others were accessed by kayaking in the Eau Claire River. Ongoing research in this region hopes to expand the lithogeochemistry and zircon petrochronology database to better delineate the geodynamic evolution and crustal architecture of this region. Determining the presence or absence of Archean basement throughout the Marshfield terrane will help refine terrane boundaries and improve our understanding of the metallogeny of the region to assist in future mineral exploration efforts. Regional Geology The Paleoproterozoic Penokean Orogen (ca. 1.8 Ga) in the Lake Superior region (Figure 1) is a classic Precambrian orogenic belt comprised of Figure 1: Geologic map of the major tectonic assemblages and major structures of the Penokean Orogen. Notable abbreviations that are important for this guidebook are EPSZ, Eau Pleine shear zone; NFZ, Niagara fault zone. Figure from Shultz & Cannon (2007). 49 �Proceedings of the 69th ILSG Annual Meeting - Part 2 dominantly submarine volcanic rocks formed in a suprasubduction zone setting that are now structurally juxtaposed along the southern edge of the Archean Superior Province during the earliest phases of forming the Columbia, or Nuna, supercontinent (LaBerge and Myers, 1984; Sims et al., 1989; Schulz and Cannon, 2007). The orogen is host to at least 150 million metric tonnes (Mt) of VMS and associated mineralization (DeMatties, 1994, 2018) but remains one of the more poorly understood and underexplored mineral districts in North America. The Penokean Orogen has been divided into the Interior and Exterior domains. These domains are sutured by the Niagara Fault Zone (Figure 1). The Exterior domain consists of passive margin, rift, and forearc basin sediments and Archean crustal blocks from the Superior Province that were deformed in the folded and faulted foreland part of the orogen. The Interior Domain consists of two accreted terranes, the Pembine-Wausau and Marshfield terranes. These terranes are sutured by the Eau Pleine Shear Zone (Figure 1). The PembineWausau Terrane is a composite accreted oceanic arc overprinted by continental-margin magmatism and hosts numerous VMS deposits and occurrences (DeMatties, 1994; Shultz & Cannon, 2007) (Figure 2). The Marshfield Terrane is composed of Archean crustal fragments of unknown origin that was overprinted by Penokean-aged magmas during the Penokean orogen (Figure 2) and is described in more detail in the sections to follow. Figure 2 - Schematic tectonic evolution of the Penokean Orogen provided by Shultz and Cannon (2007) based on geophysical, sedimentological, and geochronological compilations. continental arc volcanism and back arc extension developed until about 1850 Ma until the collision with the Marshfield terrane began. During this ocean closure, a double subduction zone with concurrent northward and southward subduction resulted in arc magmatism on both the PembineWausau and Marshfield terranes. Sedimentation related to this convergence in a foreland basin setting continued until about 1835 Ma. The end of the orogen was constrained by undeformed post-tectonic plutons dated at 1830 Ma that stich shear zones. Shultz and Cannon (2007) synthesized the tectonic events that formed the Penokean Orogen (summarized in Figure 2) based on a detailed compilation of lithologic, structural, sedimentological, and geochronological datasets. This classic model proposed that an oceanic arc, now the Pembine-Wausau Terrane, collided with the southern margin of the Superior Province around 1880 Ma. Following a subduction flip from south-directed to north-directed subduction, 50 �Proceedings of the 69th ILSG Annual Meeting - Part 2 However, this classic tectonic model for the evolution of the Penokean Orogen has recently been re-evaluated considering new U/Pb data. The first contradictory data came when Quigley (2016) obtained a high-precision U/Pb zircon age of 1832.98 ± 0.52 Ma from a rhyolite at the Back Forty deposit via CA-ID-TIMS. This younger age was in stark contrast to the other VMS deposits that yielded U/Pb zircon ages of ca. 1875 Ma. Additional U/Pb zircon ages reported by Zi et al. (2021) from volcanic units (Beecher Formation) and plutonic rocks (Dunbar Gneiss, Newingham Tonalite) in the eastern part of the orogen supported the younger extensional tectonic event proposed by Quigley (2016). These new ages resulted in a revised Penokean tectonic model where long-lived northward subduction along a continental margin with repeated extensional and contractional regimes in response to retreat and advance of the subducting oceanic plate (Figure 3). Weber and Lodge (2022) obtained a U/Pb age of 1831.4 ± 2.0 Ma on the dacite unit hosting the Eisenbrey deposit in the western part of the orogen, suggesting that this second VMS forming event was widespread. A summary of the geochronology is presented in Figure 4. Figure 3 - Schematic illustration of the revised tectonic model of the Penokean Orogen. Figure is from Zi et al. (2021). Abbreviations: NF—Niagara fault zone; EPSZ—Eau Pleine shear zone. Marshfield Terrane This guidebook visits the only Penokean volcanic complex south of the Eau Pleine Shear Zone and is interpreted to part of the Marshfield Terrane. The Marshfield Terrane represents an Archean microcontinent of uncertain origins (Sims et al., 1989; Schulz and Cannon, 2007; Zi et al., 2021). Some of the earliest works on the terrane by Sims et al. (1989) noted eight Archean U/Pb ages from isolated outcrops along the Wisconsin, Black, and Chippewa Rivers; many of which were compiled from unpublished sources. Paleoproterozoic volcanic rocks in the Marshfield terrane were deposited about 1835-1865 Ma (Sims et al., 1989; Van Wyck, 1995; Klier, 2019; Weber and Lodge, 2022). These supracrustal rocks were referred to as the Eau Claire River Complex by Cummings (1984) or the Eau Claire Volcanic Complex by DeMatties (2018; 2022). They consist of an interlayered sequence of felsic to mafic volcanic rocks, dacite porphyry, and a variety of clastic and chemical sedimentary rocks (Sims et al., 1989). Some conglomerates contain granitic gneissic clasts that were interpreted to be Archean (Myers et al. 1980), but no definitive ages were determined on the clasts. Otherwise, our knowledge of the Archean Marshfield terrane and associated Paleoproterozoic volcanic rocks remains as sparse as the outcrop exposures. Eau Claire Volcanic Complex The Eau Claire Volcanic Complex is poorly documented and understudied mainly due to its inaccessible outcrops in remote parts of the Eau Claire River valley. Myers et al. (1980) described 51 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 4 - Time-space plot for the tectonic components of the Penokean Orogen. Plot is from Zi et al. (2021). See citation for references on data sources. supracrustal amphibolites, metarhyolites and metasediments in the Eau Claire River valley and classified them as part of the Chippewa Amphibolite Complex. This informal classification of the high metamorphic grade rocks in the Eau Claire-Chippewa River area was eventually grouped with the Marshfield Terrane by Sims et al. (1989) and Shultz and Cannon (2007). The first time that that the Eau Claire “Complex” was officially referred to was by Cummings (1984) when discussing the petrology and geochemistry of the gneisses in the Big FallsLittle Falls area (Stops 1 and 2 in this guidebook). After that, research in the Eau Claire Volcanic Complex essentially ceased. Sims et al. (1989) reported a U/Pb rutile age from Big Falls of ca. 1835 Ma. In fact, the words “Eau Claire” are not used in the Shultz and Cannon (2007) regional synthesis. DeMatties (2018; 2022) refers to the Eau Claire Complex when discussing the volcanic complexes in the Penokean, but largely cites the work of Myers et al. (1980). 52 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Preliminary Hf-isotope data and zircon trace elements reveal that the rocks analyzed in the Eau Claire Volcanic Complex are juvenile, mantlederived melts with no inheritance from older sources (See Weber et al. 2023, Part 1 of this volume). This suggests that these volcanic rocks are not forming on Archean basement, as one would expect if the Eau Claire Volcanic Complex was emplaced onto the Marshfield Terrane. Additionally, magnetic lineaments on aeromagnetic maps for the region appear to crosscut the interpreted position of the Eau Pleine Shear Zone and the overall fabric as outlined by magnetics appears constant (Figure 5). Ongoing research in the region seeks to better define the relationship of the Eau Claire Volcanic Complex to the Marshfield Terrane and the architecture of the basement in this area. Field Trip Stops The overall objective of this guidebook is to tour the accessible parts of the Eau Claire Volcanic Complex as exposed in the Eau Claire River valley and surrounding tributaries. The guidebook can be divided into two main regions: The Big Falls-Little Falls and North Fork regions. The Big Falls-Little Falls region represents the classic “Eau Claire Complex” originally described by Cummings (1984). The North Fork region is much more remote and rarely visited by geologists. In fact, it is not obvious that anyone has studied these rocks since they were first reported by Myers et al. (1980). These more remote parts of the complex are currently being studied (see Leahy and Lodge, Part 1 of this volume) to determine their regional context. Some of that data will be presented herein. The goal of this work is to determine if the Eau Claire Volcanic Complex is a volcanic center built upon Archean crust (continental arc) or is juvenile Figure 5 - Total field aeromagnetic map of the Eau Claire River region showing the location of Eau Pleine Shear Zone and field trip regions (Big Falls, North Fork). White dashed lines highlight a couple of magnetic lineaments that extend through the suturing shear zone. Magnetic maps from Daniels and Snyder (2002). 53 �Proceedings of the 69th ILSG Annual Meeting - Part 2 (oceanic arc) as this is important implications for the regional metallogeny and mineral systems. Most of the locations in this guidebook are on riverside outcrops. These areas are prone to sudden flooding and the upmost caution and careful planning should be used prior to visiting these locations. In addition, rocks here are uneven and potentially slippery. To access larger sections of outcrops, low water conditions may be required. In addition, all locations in this region may contain poisonous plants (e.g. nettle, poison ivy) and black-legged ticks that can transmit diseases. While this is unlikely to be a concern in early spring during the 2023 ILSG conference, future users of this manual should plan appropriately. Figure 6 - Generalized Precambrian geologic map of the Big Falls-Little Falls area of the Eau Claire River. Figure modified from Cummings (1984). Big Falls Region The banded amphibolite, gneisses, and intrusions in the Big Falls region of the Eau Claire River are some of most studied Precambrian exposures in this region and are visited multiple times a year by introductory and upper division geology classes at the University of WisconsinEau Claire. It is in this region that the term “Eau Claire River Complex” was first introduced by Cummings (1984) and this terminology has since been adopted by others (e.g. DeMatties, 2018) to describe the volcanic rocks present in the Marshfield Terrane. Figure 7 - Metamorphic conditions from geothermobarometic studies at Big Falls indicated by the yellow star. Data is from unpublished student project at the University of Wisconsin-Eau Claire. The region consists of mostly amphibolitic and felspathic gneisses that are intruded and brecciated by tonalite (Figure 6). Regional metamorphism in this region is at lower to upper amphibolite facies. A sample of amphibolitic gneiss from the Eau Claire Volcanic Complex using the edenite-richterite thermometry determined temperatures between 719-769 °C (Hannack and Radwany, 2018). Unpublished data from University of Wisconsin-Eau Claire class projects using garnet-biotite thermobarometry estimate peak metamorphic conditions at 765 °C and 11.5 kbars (Figure 7). A rutile U/Pb age of 1835 Ma from Sims et al. (1989) in the Eau Claire Volcanic Complex may indicate the timing of metamorphism. New research in this region provides our first glimpse into the trace element characteristics of these rocks (Figure 8). Rocks from both Big Falls and Little Falls have mafic protoliths with EMORB to oceanic arc like abundances of Th, Nb, and Yb (Pearce, 2008). On normalized trace element diagrams, samples have elevated LREE, low Th/La ratios, negative Nb and Ti anomalies. These trace element characteristics features are common in back-arc environments. Additionally, feldspathic units sampled have extremely 54 �Proceedings of the 69th ILSG Annual Meeting - Part 2 depleted trace element signatures and positive Eu anomalies, suggesting that they may be fractionated crystal cumulates. This broadly supports the interpretation of Cummings (1984) that the protolith of the Big Falls gneisses are a layered mafic intrusion. Stop 1: Amphibolite Gneisses and the “Great Unconformity” at Big Falls County Park Lat: 44.8215° Long: -91.2953° Figure 8 – Preliminary trace element geochemistry from the Big Falls-Little Falls area of the Eau Claire Volcanic Complex. Top: Trace element classification diagram from Pearce (1996) modified from Winchester and Floyd (1977). Middle: Mantle source discrimination diagram from Pearce (2008). Bottom: Primitive mantle-normalized trace element diagram using values from Sun and McDonough (1989). This location is accessible from the north entrance to Big Falls County Park off Eau Claire County Highway Q. There is a parking lot at this entrance with plenty of parking for park visitors. Follow the paved foot path eastward toward the river. Once on the riverbank, walk northward for 55 �Proceedings of the 69th ILSG Annual Meeting - Part 2 about 50 m to reach the outcrops at the falls. Note that outcrops on the south bank of the falls will have to be accessed via the south entrance to the park on County Highway K. During very low water conditions, it is possible to hop across the outcrops to access the south bank. This region has some steep-edged rock cliffs adjacent to the river and there are springs that keep some areas wet and slippery. Please watch your step. This stop highlights the geology along the north side of Big Falls County Park where the rocks are exposed along the Eau Claire River. In addition to the Precambrian rocks, this location also has a great exposure of the “Great Unconformity” with overlying Cambrian Mount Simon Formation. The Eau Claire River flows along the nonconformity between the Cambrian and Precambrian rocks, where the river has eroded the overlying Cambrian units away exposing the Precambrian basement rocks. At this stop, we highlight four locations that highlight different units seen here at Big Falls County Park (Figure 9). Photo 1: Photographs of the banded amphibolitic gneiss at Big Falls County Park. (A) Banded amphibole gneiss at Big Falls. B: Photomicrograph in plane-polarized light (25x) of large garnet porphyroblasts in quartzofeldspathic and hornblende matrix. Location 1: The Banded Amphibole Gneiss The banded amphibole gneiss (Photo 1A) is best described as a fine-grained banded gneiss with alternating hornblende-rich and plagioclaserich layers. The hornblende-rich layers range anywhere from less than 1 cm to ~15 cm and contain about 85% hornblende and 15% granulated plagioclase with sparse idioblastic garnet. The plagioclase-rich layers are consistently thicker and contain approximately 15% hornblende. The garnets though scarce occur as coarse grained porphyroblasts in both layers (Photo 1B) although these garnets often show retrograde alteration back to hornblende. The garnets are typically poikioblastic (Photo 2) with quartz, plagioclase and occasionally biotite inclusions. The hornblende occurs as euhedral to subhedral grains and the plagioclase as very-fine grained, dynamically recrystallized, matrix. The granulated plagioclase is typically labradorite to bytownite but anorthite (An92) occurs as cores in some of the idioblastic hornblende to create an Photo 2: Photomicrograph in plane polarized light of poikioblastic garnet in a hornblende and granulated plagioclase matrix (50X magnification). unusual bi-modal plagioclase population (Photo 3). Multiple shear zones and isoclinal folds are present throughout the outcrop, providing evidence for multiple deformation periods. Partially annealed shear zones can be traced across almost the entire unit that truncate and offset banding. There are also asymmetric 56 �Proceedings of the 69th ILSG Annual Meeting - Part 2 amphibole schist is enriched in MgO and FeO and depleted in CaO and Al2O3 in comparison to the banded amphibole gneiss (Table 1). Both major element (Table 1) and trace elements (Figure 8) characterize this as a MORB-like composition. Isoclinal folds of the foliation and the presence of ductile shear zones indicate deformation throughout this unit. The contact between the banded amphibole gneiss and the amphibole schist is buried by slumping blocks of the Cambrian Mount Simon Formation and vegetation. Photo 3: Photomicrograph in partially crossed polars of idioblastic hornblende with anorthite cores (An 92) in a matrix of granulated plagioclase (An72) in the banded amphibole gneiss at Big Falls (Magnification is 50x). amphibolite inclusions kinematics. that show variable This unit was sampled for a recent zircon petrochronology study and produced significant results that question what is currently understood about the southern portion of the Penokean Orogen. This unit yields a U/Pb age of 1874.7 ± 2.1 Ma which temporally correlates with other VMS-forming events across the PembineWausau terrane. Zircon trace element geochemistry of the sample indicate the sample formed in a hydrated but reduced melt in a backarc setting where decompression was occurring in a metasomatized mantle (Weber and Lodge, 2022). Hf-Lu data from the banded amphibolite gneiss indicates a lack of older basement inheritance. The zircon petrochronology from these rocks contradicts the interpretation that Eau Claire Volcanic Complex was emplaced into the Archean Marshfield Terrane. These results have motivated additional research in the Eau Claire Volcanic Complex. Photo 4: Outcrop photo of the feldspathic gneiss at Big Falls. Location 3: Transition Gneiss and Feldspathic Gneiss The amphibole schist gradually grades into the transition gneiss for a few meters as the unit contains fewer amphibole-rich layers and the plagioclase rich layers become more prominent (Photo 4). The feldspathic gneiss is primarily made of plagioclase, with 10-20% hornblende and lesser amounts of chlorite, epidote, and localized sulfidation with some pyrite mineralization. Location 2 Amphibole Schist Despite strong metamorphic recrystallization and structural fabric overprinting, there are some primary igneous textures that are preserved (Cummings, 1984). The compositional banding and layering throughout all units appear to be The further west along the Eau Claire River, the amphibole schist is exposed. This unit is best described as a dark green to black, fine grained thinly banded amphibole schist. Hornblende is the primary amphibole with lesser amounts of plagioclase. Based on whole rock XRF data, the 57 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 9: Geologic map showing outcrop locations at the Big Falls stop. Modified from Cummings (1984). Table 1. Whole rock major element geochemistry (via XRF) from Big Falls for banded amphibole gneiss (location 1), amphibolite (location 2), and altered rocks at the Precambrian-Cambrian contact (location 3). Average MORB composition (Winters, 2010) is included for comparison. Unit Unaltered Banded Gneiss 1 Banded Gneiss 2 Banded Gneiss 3 Altered (Depth) surface .5m 1.0m 1.5m Unaltered Amphibolite 1 Amphibolite 2 Average MORB (Winter 2010) Altered (Depth) surface .25m .5m .65m .75m 1.0m SiO2 TiO2 Al2O3 Fe2O3T CaO MgO MnO Na2O K2O P2O5 Totals 47.10 48.43 46.63 0.17 0.21 0.23 30.43 30.56 30.24 2.14 3.35 2.47 15.18 14.65 14.51 0.72 1.38 0.88 0.03 0.04 0.03 2.21 2.97 2.85 0.20 0.25 0.18 0.05 0.04 0.03 98.23 101.88 98.05 52.06 50.26 52.55 52.92 0.44 0.74 0.34 0.32 16.66 15.28 17.36 18.23 6.72 11.56 7.28 5.79 0.88 0.63 1.06 0.80 5.21 6.18 5.17 4.91 0.04 0.05 0.03 0.02 0.11 0.05 0.05 0.09 9.28 9.14 9.04 9.37 0.03 0.28 0.03 0.03 91.43 94.17 92.91 92.48 51.10 52.66 50.50 1.34 1.71 1.56 15.50 13.25 15.30 13.73 12.12 11.50 9.07 8.05 11.50 5.79 6.57 7.47 0.19 0.20 n/a 3.11 3.56 2.62 0.29 1.46 0.16 0.23 0.17 0.13 100.35 99.75 100.74 61.93 62.79 61.48 62.62 60.07 58.69 0.94 0.99 0.84 0.88 0.95 0.87 17.36 17.18 17.04 16.26 16.84 16.31 4.98 6.10 5.04 5.42 5.60 7.30 0.63 0.65 0.64 0.64 0.64 0.66 2.70 3.05 3.02 2.68 2.89 3.24 0.02 0.04 0.02 0.04 0.04 0.07 0.32 0.20 0.21 0.23 0.07 0.08 7.10 7.22 6.97 7.15 7.45 7.18 0.19 0.19 0.18 0.18 0.21 0.19 96.17 98.41 95.44 96.10 94.76 94.59 58 �Proceedings of the 69th ILSG Annual Meeting - Part 2 primary. Anorthositic autoliths are incorporated in a fine-banded, more mafic matrix near the transitional gneiss. The banding in the autolith is discordant to banding in the matrix and appear to be concentrated in bands but are not associated with boudinage fabrics. These observations were critical in interpreting the protolith of this region. Location 4: The Great Unconformity and the basal portion of the Mt. Simon Formation The large hillside on the north bank of the river and above the Precambrian outcrops is the Cambrian Mount Simon Formation. The base of the Mt. Simon Formation is a mix of coarsegrained quartz arenites and quartz pebble conglomerates. Photo 5: Nonconformity between the Cambrian Mount Simon Formation and the amphibolites at Big Falls County Park. The Great Unconformity creates a nonconformable contact between the Precambrian units at the previous three locations and the base of the Mt. Simon Formation. At Big Falls, a thin blue-green celadonite clay layer (Figure 10) has formed along the nonconformity as a result of Kmetasomatism from basinal brines. The Kmetasomatism at the unconformity is recognized throughout the midcontinent region and is related to MVT lead zinc deposits in the Tri-state region (See field trip 1 in this volume). Locally the celadonite acts as a fluid barrier for springs that flow along the unconformity. In other places, the contact appears to be relatively sharp with little alteration (Photo 5). Figure 10: A-CN-K diagram showing chemical change due to weathering and the alternative path of Kmetasomatism. The celadonite at Big Falls is not a weathering profile and requires adding substantial potassium and to produce the celadonite and authigenic K-spar seen along the unconformity (see Table 1 for chemistry). Stop 2 –Tonalite Breccia and Gneisses at Little Falls. Lat: 44.8103° Long: -91.2825° bridge at this location for the Eau Claire River flood stage measurement. Just north of the bridge there is a small parking area on the west side of the road. There are several small foot paths that lead down to the river’s edge. The outcrops are mostly exposed immediately around and under the bridge. The quality of exposure here changes all the time as flooding conditions sometimes This location is just on the north side of the County Highway K bridge that crosses the Eau Claire River and is 300 m north of the exit to the south entrance of Big Falls County Park. Google Maps calls this place the East Eau Claire Canoe Landing, but the USGS refers to this location as Little Falls (so does the faculty and students at the University of Wisconsin-Eau Claire) and uses the 59 �Proceedings of the 69th ILSG Annual Meeting - Part 2 buries parts of the outcrop with sand and downed vegetation. To access the south bank of the river, a short bush traverse (100-300 m) will be required from the southside of the bridge along the riverbank. If water level and time permit, this stop has four locations of interest that highlight the intrusive history in the region. The outcrops in this area expose an inclusion-rich intrusive contact between a foliated tonalite and lensoidal amphibolite and are cut by younger pegmatitic and mid-continent rift diabase dykes (Figure 11). This location is used to teach students at the University of Wisconsin-Eau Claire about interpreting relative geologic time and observing contact relationships. The absolute ages of these rocks are unknown as recent attempts to isolate zircons from the tonalite were unsuccessful. Photo 6: Gneissic tonalite breccia highlighting some of the banded gneiss xenoliths. Some of the smaller xenoliths here are elongated. significant assimilation of amphibolite. Biotite commonly produces a crude foliation that may have formed from hornblende during a later deformation. Location 1: Gneissic Tonalite Breccia It is clear the tonalite is metamorphosed and is an important part of determining the nature of the Eau Claire Volcanic Complex. However, efforts to constrain the timing of this intrusive event have yielded conflicting results. Van Schmus (1980) yielded a U/Pb age of 1842 ± 10 Ma utilizing zircon fractions (i.e. not modern single crystal methods). Sims et al. (1989) reported a U/Pb age of 1856 ± 5 Ma from a xenolith at Little Falls. Assuming that the amphibolite xenoliths at Little Falls are from the same amphibolite unit at Big Falls that was dated at 1875 Ma, then there is a clear conflict. The tonalite was sampled for that recent petrochronologic study (Weber and Lodge, 2022) but yielded very few zircons. Resolving the timing of emplacement and tectonic setting of this intrusion will help better understand the geodynamic setting of the Eau Claire Volcanic Complex. The gneissic tonalite breccia is the most prominent unit at Little Falls (Photo 6). Roughly 90% of xenoliths in the breccia are characterized as banded gneiss to banded amphibolite containing 50-80% hornblende and 20-40% plagioclase with lesser amounts of biotite. These xenoliths range in size anywhere from less than 1cm to greater than 20 cm, and they are hosted in a biotite tonalite intrusion which destroys the older banded gneiss. The banded gneiss xenoliths are also elongated and contain folds. Ultramafic xenoliths are scarce but also present. These xenoliths contain over 90% hornblende with lesser amounts of epidote-clinozoisite and plagioclase. Occurring in localized clusters, the fragmented ultramafic xenoliths indicate these were most likely part of a larger block but separated during the tonalite intrusion event (Myers et al., 1980). The tonalite is composed of 35-40% plagioclase (An50-55), about 30% hornblende, 25-30% quartz, 5-10% biotite, and accessory epidote. Myers et al. (1980) interpreted the fabric in the rock as flow-lamination, however it is parallel to regional magnetic lineaments suggesting it may be a structural fabric. Large variation in mafic mineral abundance indicates Location 2: Diabase Along the north side of the river and east of the bridge, lies one of many mid-Proterozoic diabase dykes associated with the mid-continent rift in the 60 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 11: Geologic map of the Little Falls area showing the locations of interest at this stop. Figure modified from Myers et al (1980). Eau Claire region. Like many other diabase dike outcrops in the area, this diabase exhibits both clean columnar jointing and well-defined chilled margins. This diabase is only a few meters in size and disappears beneath the surrounding overburden (Figure 11). The diabase has a medium-grained, equigranular texture and does not have any foliation or recrystallization textures and is clearly post-metamorphism. throughout the Eau Claire volcanic complex along the Eau Claire River where the Precambrian rocks are exposed. Their macro- and microscopic characteristics indicate they are Location 3: Pegmatite Dike On the west bank of the river lies a 2 m wide pegmatite dyke (Photo 7). Outlier boulders of this pegmatite can be found on the eastern bank of the river. The alkali-feldspar crystals in this outcrop reach sizes greater than 30 cm. Various sizes of quartz veins also crosscut this unit. This granite pegmatite dike is one of a handful seen Photo 7: 18m-wide pegmatite in the Eau Claire River downstream from Little Falls. 61 �Proceedings of the 69th ILSG Annual Meeting - Part 2 clearly younger than the Penokean deformation and metamorphism and could be related to Mazatzal or Yavapai orogenic events to the south like the Wolf River Batholith in northcentral Wisconsin. The mineralogy of the pegmatites is very complicated with many accessory carbonate, phosphate and oxide phases enriched in Nb, Y, F U, Th and REE. Zircon in the pegmatites indicate extreme fractionation (Figure 12). The zircons also show considerable xenotime (Y,P) substitution and considerable solid solutions with both coffinite (USiO4) and thorite (ThSiO4). The pegmatites, despite their pink color, are primarily composed of plagioclase with an overprint of potassic alteration. Most of the alkali-feldspar occurs along cleavages, crystal boundaries and fractures indicating it is a late phase in pegmatite formation. The plagioclase in the pegmatites is primarily albite but ranges from An0 to An30. The euhedral and inclusion free garnets (Photo 8) have a limited range of chemistry close to 50% almandine and 50% spessartine which is similar to magmatic garnet compositions in other garnet-quartz-albite pegmatites (Muller et al., 2018). Figure 12. Zr/Hf in pegmatites from the Eau Claire River Complex. The Eau Claire River pegmatites have many characteristics of pegmatites in the Nb/Y/F (NYF) family of rare element pegmatites and NYF pegmatites are always associated with metaluminous to alkaline (or peralkaline) granites (Cerny and Ercit, 2005) Location 4: Amphibolitic Gneiss The xenoliths within the tonalite are assumed to be derived from the nearby outcrops of the amphibolitic gneisses. Unlike the planar banding at Big Falls, the amphibolitic gneisses here is more lensoidal with cm- to dm-scale lens-shaped, hornblende-rich pods surrounded by more plagioclase-rich “matrix” and quartz-veining. Photo 8. Top: Photomicrograph (25X in plane polarized light) of garnet cluster in quartz and albite from Little Falls pegmatite dike on the west side of the river. Bottom: Almandine/spessartine garnet clusters at the same location at Little Falls are magmatic in origin. 62 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Detailed work has not been completed on these outcrops but are assumed to be petrogenetically related to the amphibolites at Big Falls. Future research will examine these exposures more closely. the trace element geochemistry and zircon petrochronology of the rocks in this region to make better links with the rest of the Eau Claire Volcanic Complex. Much of that data is still pending or preliminary, so results will be forthcoming soon. The goal for the field trip in this region is to show as many of the rocks as possible, regardless of how much we know about them. North and South Fork Region This is the part of the trip where information on these rocks is sparse and new data is only just becoming available. To our knowledge, the rocks in the North and South Fork areas of the Eau Claire River have not been studied in any detail since Myers et al. (1980). Much of the area is remote and sparsely developed and very few outcrops are easily accessible. Field work in the 2022 summer relied on one-way, day-long kayak trips along different segments of the North Fork. Aside from the occasional powerline, field work on these stretches of the Eau Claire River felt wild and remote. This field work aimed to characterize The region consists of amphibolites, feldspathic gneisses, and foliated granitoids and are cross-cut by younger, undeformed granitic pegmatites (Figure 13). A metarhyolite from this region yielded an age of 1858 ± 5 Ma (Sims et al, 1989) and was one of the key samples that linked Penokean volcanic processes to the Marshfield terrane. Myers et al. (1980) interpreted mappable contacts between intrusions and foliated Figure 13: Geologic map of the North and South Fork of the Eau Claire River in eastern Eau Claire County and western Clark County. Figure modified from Myers et al. (1980). 63 �Proceedings of the 69th ILSG Annual Meeting - Part 2 supracrustal rocks in this area to be sheared and nearly vertical and that they enclose lensoidal fault slices which have been juxtaposed mainly by strike-slip displacement. Outcrops of amphibolite in the southern part of the map (Figure 13) near the confluence of the North and South Forks of the Eau Claire River were interpreted to be part of the “Chippewa Amphibolite Complex” (Myers et al., 1980) which is broadly supported by regional aeromagnetic maps (Figure 5). Myers et al. (1980) interprets the volcanic rocks in this region to unconformably on amphibolites, but geochronologic data is lacking to make any absolute local or regional correlations. Regional metamorphic grade is estimated to be upper greenschist to lower amphibolite based on the presence of garnet, epidote, muscovite, and hornblende. Preliminary geochemical results from the North Fork region begin to reveal the setting of these volcanic and intrusive rocks. Volcanic protoliths are bimodal (Figure 14) with tholeiitic mafic rocks with oceanic affinities (Figure 15) and FI- to FII-type felsic rocks arc-like affinities (Figure 16). More work needs to be done before we can concretely interpret the setting of this region of the Eau Claire Volcanic Complex. Figure 15: Trace element geochemical characteristics of the mafic rocks from the North Fork region of the Eau Claire River. Top: Magmatic affinity diagram for sub-alkaline basalts from Ross & Bedard (2009). Middle: Mantle source discrimination diagram from Pearce (2008). Bottom, Primitive mantle-normalized trace element diagram using values from Sun and McDonough (1989). Figure 14: Trace element classification diagram from Pearce (1996), modified from Winchester & Floyd (1977). 64 �Proceedings of the 69th ILSG Annual Meeting - Part 2 These settings are not typical of continental settings, which continues to question the relationship between the Eau Claire Volcanic Complex and Marshfield Terrane. Stop 3 – Amphibolite and Intrusions at Knights Pool Lat: 44.7482° Long: -90.9669° Figure 16 – Trace element geochemical characteristics of felsic rocks from the North Fork region of the Eau Claire River. Top: Nb/Y discrimination diagram for granites from Pearce (1984). Middle: F-type felsic discrimination diagram from Hart et al. (2004). Bottom: Primitive mantle-normalized diagram using values from Sun & McDonough (1989). The directions to get to this stop are a little more elaborate since it is in a more remote location. From the community of Augusta, take State Highway 27 north for 4.4 miles to County Road GG. Turn east on to County Road GG and drive 4.7 miles to the intersection of Channey 65 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Road just after the bridge over the Eau Claire River. Turn east on Channey Road (note that this is an unpaved road) and drive for 4.6 miles until the road crosses the North Fork of the Eau Claire River. This location is called Knights Pool and is labelled by signage. The accessible outcrops in this region are immediately beneath the bridge and are accessible by foot trails. There are larger outcrops north of the bridge that are accessible by a small, 150 m bush traverse along a sparsely used trail. At both locations, rocks are immediately adjacent to a shallow but fast-moving river and caution should be used. Complex exposed in this section of the river upand downstream of this location. However, this is the only easily accessible section by foot. At Knights Pool, there are mostly strongly foliated and deformed amphibolites that are intruded by a biotite granodiorite (Figure 17). Amphibolite: The amphibolite at Knights Pool is characterized by a fine to very fine grained mafic lineated amphibolite with stretched quartzfilled amygdules, relict pillow structures, and wispy textures suggesting a mafic flow (Photo 9). Thin sections of the amphibolite clearly show the lineations present in the amphibolite here (Photo 10). Several stages of deformation occurred starting with the amphibolite being isoclinally folded, then intruded by aplite veins, and intruded by large granodiorite body (Myers et al., 1980). The shearing in of the granodiorite body created a mylonite gneiss along the contact with the amphibolite. Knights Pool is located at the bridge on Channey Road as it crosses the North Fork of the Eau Claire River along the southern edge of the North Fork Eau Claire River State Natural Area. There is more of the Eau Claire Volcanic Photo 9: Outcrop of the amphibolite showing both the isoclinal folds and strained amygdules present in the unit. Trace element geochemistry of the amphibolites at Knights Pool are notably LREEdepleted with strong negative Nb anomalies (Figure 15). This suggests it was derived from strongly depleted but metasomatized mantle. This type of environment, presumably a mature backarc, rarely exists in a continental setting. The granitoids in the map area have classic enriched LREE and Th with depleted Nb and HREE signatures suggesting they are related to a Figure 17: Geologic map of the Knights Pool area. Map is modified from Myers et al. (1980). 66 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Photo 10: Photomicrographs in plane-polarized light of the amphibolite at Knights Pool amphibolite under thin section at 25x magnification (A) and 100x magnification (B). Hornblende forms a clear lineation. Photo 11: Photomicrographs of the biotite granodiorite at Knights Pool in (A) plane-polarized light, and (B) cross-polarized light. Both images are 25x magnification. the village of Rock Dam. Turn northward on Butler Road and use the parking lot on Hay Creek Lake just south of the bridge over Hay Creek. The outcrop of phyllite are under the bridge and near the Rock Dam spillway. The nonconformity and metarhyolite can be better accessed from within the Rock Dam Campground near campsite 90. different tectonic event when the crust was thicker, and garnet was stable to deplete HREE. Granodiorite Intrusion: The medium to coarse grained biotite granodiorite intruded the amphibolite creating a mylonitic fabric along the contact. The intrusion, shearing along the contact, caused the folding of the aplite veins seen in the amphibolite. Quartz is strongly recrystallized and biotite concentrations define a weak foliation. Thin section photos highlight how the quartz is being recrystallized, as well as show the alignment of biotite aggregates (Photo 11). This location reveals another nonconformity between the Precambrian and Cambrian Mount Simon Formation. The metarhyolites and phyllites in this area are strongly mylonitized and primary structures are difficult to interpret. The metarhyolite at this location described by Myers et al. (1980) is the only reference to a rhyolitic unit in the Eau Claire Volcanic Complex. Since Sims et al. (1989) dated a metarhyolite at 1858 ± 5 Ma in the Eau Claire River and cited Myers et al. (1980), it presumably came from this location. If that is the case, then the rocks at Rock Dam are of regional significance because it is one of Stop 4 – Metarhyolite and Phyllite at Rock Dam Lat: 44.7338° Long: -90.8469° From the previous stop, continue eastward on Channey Road until it ends at County Highway H. Turn southward and drive 1.5 miles to Rock Dam Road. Turn eastward and take this road into 67 �Proceedings of the 69th ILSG Annual Meeting - Part 2 estimated mineral percentages and matrix of this rock is composed of a very fine-grained alkalifeldspar (57%), quartz (35%), muscovite (3%), magnetite (2%), and biotite (1%). The quartz eyes along with the absence of feldspar porphyroclasts suggests that the quartz either originated as phenocrysts or clasts in a tuff (Myers et al. (1980). Foliation trends east-west and is near vertical. Phyllite: Closer to the base of Rock Dam lies a muscovite-rich phyllite composed of alkalifeldspar, quartz, and muscovite (Photo 12). This outcrop lacks both the quartz eyes and biotite possibly indicating a separate protolith than the metarhyolite (Myers et al. 1980). Photo 12: Outcrop photo of strongly foliated phyllite at Rock Dam near spillway. Cambrian strata can be seen in background on opposite bank of river. Mt. Simon Formation: The basal part of the Mt. Simon Formation, a conglomerate layer containing pebbles of vein quartz and rhyolite, is exposed at this location (Photo 13). The contact between the Mt. Simon and the Precambrian metarhyolite shows about 5 m of relief. Many of the locations exposing the Great Unconformity in the Eau Claire region show deep weathering of the underlying Precambrian rocks, however there is not much weathering of the Precambrian metarhyolite here. the very few dated Penokean supracrustal rocks within the Marshfield terrane. Mylonitized Metarhyolite: Myers et al. (1980) admittingly conceded that determining the protolith of this outcrop can be challenging considering the similarities between sheared porphyritic rhyolites and leucogranites. The mylonite here is pale pink metamorphosed porphyritic rhyolite containing quartz eyes that can be described as phenocrysts or clasts. These quartz eyes are roughly 1-2.5 mm in size and under thin section show a subrectangular to lenticular shape (Myers et al. (1980). The 68 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Photo 13: Basal pebble conglomerate in Cambrian strata overlying metarhyolite at Rock Dam. Stop 5 – Metavolcanic Rocks at Mead Lake Lat: 44.7885° Long: -90.7742° From the previous stop, continue northward on Butler Road for 0.8 miles to the intersection with Willard Road. Drive eastward on Willard Road for 2.0 miles and turn north onto County Road M. Drive northward on County Road M for 1.6 miles and turn eastward onto Rocky Run Road. Drive 1.2 miles on Rocky Run Road and turn northward on Bruce Mountain Road that will turn into South Lake Road. South Mead Lake Park will be 1.4 miles down this road. Park there, and the outcrops are on the riverbank west of the Mead Lake Dam spillway. The bedrock exposed at this location is primarily a foliated, fine-grained chloritic metavolcanic rock (Photo 14). There has been no known study of this rock, and our data is still pending. Nonetheless, it is apparent that the metamorphic grade seems to be decreasing in this part of the Eau Claire Volcanic Complex. This is in stark contrast to the rocks in the Chippewa River valley (Fieldtrip 1, this volume) and Big Falls region (Stops 1-2). Future work in the region will utilize every outcrop, even small ones like this location, to better describe and define the tectonics and metallogeny of the Eau Claire Volcanic Complex. Photo 14: Outcrop photo of metavolcanic rocks at Mead Lake Dam. 69 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Wisconsin: An overview: Economic Geology, v. 89, p. 1122-1151. Acknowledgements Despite decades of regular visits from groups from the University of Wisconsin-Eau Claire, the most extensive detailed maps and rock descriptions were provided by Paul Myers and collaborators in the 1980 ILSG guidebook. Outside of Big Falls County Park, many of those locations have not been visited since then. A lot of the geologic descriptions from those lesserknown areas have been updated from Myers et al. (1980) and figures have been digitized while adding new data and insights where available. DeMatties, T. A., 2018, Effects of paleoweathering and supergene activity on volcanogenic massive sulfide (VMS) mineralization in the Penokean Volcanic Belt, northern Wisconsin, Michigan and east-central Minnesota, USA: Implications for future exploration: Ore Geology Reviews, v. 95, p. 216-237. DeMatties, T. A., 2022, Exploration-resource assessment of productive felsic volcanic centers in the Paleoproterozoic Penokean Volcanic Belt of northern Wisconsin, Michigan and east-central Minnesota, USA: Ore Geology Reviews, v. 141, article 104489. In addition, the authors of this guidebook would like to thank the countless undergraduate and graduate students that have worked on these outcrops and have continued to inspire new work in the region. Specific acknowledgement is deserving to Matt Leahy and his undergraduate research project in the North Fork region in providing some insight into that part of the complex. Hannack, G., and Radwany, M., 2018, HornblendePlagioclase thermometry of the Eau Claire River Complex, western Wisconsin: Proceedings of the Institute on Lake Superior Geology 64th Annual Meeting, Iron Mountain, Michigan, p. 47-48. Hart, T. R., Gibson, H. L., and Lesher, C. M., 2004, Trace element geochemistry and petrogenesis of felsic volcanic rocks associated with volcanogenic massive Cu-Zn-Pb sulfide deposits: Economic Geology, v. 99, p. 1003-1013. References Klier, J. J., 2019, The Marshfield Terrane: Refedinition of origin through zircon geochronology and geochemistry: Unpub. M.S. thesis, Ball State University, 115 p. Brown, B. A., 1988, Bedrock geology of Wisconsin, west-central sheet, Wisconsin Geological and Natural History Survey Map 87–11b. Cummings, M. L., 1984, The Eau Claire River complex: A metamorphosed Precambrian mafic intrusion in western Wisconsin: Geological Society of America Bulletin, v. 95, p. 75-86. LaBerge, G. L., 1996, Volcanogenic massive sulfide deposits of northern Wisconsin: A commemorative volume, Proceedings of the 42nd Annual Meeting of the Institute on Lake Superior Geology, Cable, Wisconsin. Cerny, P. and Ercit, T. S., 2005, The classification of granitic pegmatites revisited. Canadian Mineralogist, v.43, p. 2005-2026. LaBerge, G. L., and Myers, P. E., 1984, Two early Proterozoic successions in central Wisconsin and their tectonic significance: Geological Society of America Bulletin, v. 95, p. 246-253. Daniels, D. L., and Snyder, S. L., 2002, Wisconsin aeromagnetic and gravity maps and data, U.S. Geological Survey Open-File Report 02-493. Myers, P. E., Cummings, M. L., and Wurdinger, S. R., 1980, Precambrian geology of the Chippewa Valley, Wisconsin, Institute of Lake Superior Geology 26th Annual Meeting, Eau Claire, Wisconsin, Field Trip Guidebook 1, 123 p. DeMatties, T. A., 1989, A proposed geologic framework for massive sulfide deposits in the Wisconsin Penokean volcanic belt: Economic Geology, v. 84, p. 946-952. Muller, A., Spratt, J., Thomas, R., Williamson, B.J., and Seltmann, R., 2018, Canadian Mineralogist, v. 56, p. 657-687. DeMatties, T. A., 1994, Early Proterozoic volcanogenic massive sulfide deposits in 70 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Pearce, J. A., 1996, A users guide to basalt discrimination diagrams: Trace Element Geochemistry of Volcanic Rocks: Applications for Massive Sulphide Exploration. Geological Association of Canada, Short Course Notes, v. 12, p. 79-133. pre- and early Proterozoic rocks in Wisconsin: Unpub. Ph.D. thesis, University of Wisconsin Madison, 295 p. Van Wyck, N., and Johnson, C. M., 1997, Common Lead, Sm-Nd, and U-Pb constraints on petrogenesis, crustal architecture, and tectonic setting of the Penokean orogeny (Paleoproterozoic) in Wisconsin: Geological Society of America Bulletin, v. 109, p. 799-808. Pearce, J. A., 2008, Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust: Lithos, v. 100, p. 1-4. Weber, E. M., and Lodge, R. W. D., 2022, New U/Pb Geochronology from the Proterozoic Penokean Orogen, Wisconsin: Implications for VMS Metallogeny: Society of Economic Geologists Annual Meeting, Denver, CO, paper P5.10. Pearce, J. A., Harris, N. B. W., and Tindle, A. G., 1984, Trace element discrimination diagrams for the tectonic interpretation of granitic rocks: Journal of Petrology, v. 25, p. 956-983. Quigley, A., 2016, Setting of the volcanogenic massive sulfide deposits in the Penokean Volcanic belt, Great Lakes region, USA: Unpub. M.S. thesis, Colorado School of Mines, 95 p. Winchester, J. A., and Floyd, P. A., 1977, Geochemical discrimination of different magma series and their differentiation products using immobile elements: Chemical Geology, v. 20, p. 325-343. Ross, P.-S., and Bédard, J. H., 2009, Magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace-element discriminant diagrams.: Canadian Journal of Earth Sciences, v. 46, p. 823-839. Winter, J. D., 2010, An Introduction to Igneous and Metamorphic Petrology, Prentice Hall, 697p. Zi, J-W., Sheppard, S., Muhling, J. R., and Rasmussen, B., 2021, Refining the Paleoproterozoic tectonothermal history of the Penokean Orogen: New U/Pb age constraints from the PembineWausau terrane, Wisconsin, USA: Geological Society of America Bulletin, v. 134, p. 776-790. Schulz, K. J., and Cannon, W. F., 2007, The Penokean orogeny in the Lake Superior region: Precambrian Research, v. 157, p. 4-25. Sims, P. K., Van Schmus, W. R., Schulz, K. J., and Peterman, Z. E., 1989, Tectonostratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: Canadian Journal of Earth Sciences, v. 26, p. 21452158. Sun, S., and McDonough, W. F., 1989, Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes, in Saunders, A. D., and Norry, M. J., eds., Magmatism in the Ocean Basins, Geological Society Special Publication, v. 42, p. 313-345. Van Schmus, W. R., 1980, Chronology of igneous rocks associated with the Penokean orogeny in Wisconsin: Geological Society of America Special Paper, v. 182, p. 159-168. Van Wyck, N., 1995, Oxygen and carbon isotopic constraints on the development of eclogites, Holsnpy, Norway, and, Major and trace element, common Pb, Sm-Nd, and zircon geochronology constraints on petrogenesis and tectonic setting of 71 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Field Trip 4 – Quaternary Geology and Geomorphology of the Eau Claire Region Douglas J. Faulkner Department of Geography and Anthropology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 J. Elmo Rawling, III Wisconsin Geological and Natural History Survey, Madison, WI 53705 Phillip H. Larson Earth Science Programs, EARTH Systems Laboratory, Minnesota State University Mankato, Mankato, MN 56001 72 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Introduction Eau Claire lies close to the outermost edge of the former Chippewa Lobe of the Laurentide Ice Sheet as it existed during late Wisconsinan time (MIS-2) (Fig. 1). To the south are older glacial deposits and then the Driftless Area, which apparently was never glaciated. This all-day field trip will concentrate on three aspects of the region’s landscape development from the late Wisconsinan to the late Holocene: glacial, fluvial and aeolian. Glacial Landscapes Northern Wisconsin was glaciated multiple times in the Quaternary. The oldest glacial deposits were derived from the northwest and were likely deposited prior to 780,000 ka. These include the Pierce and Marathon Formations (Rawling et al., in review; Syverson et al., 2011). These deposits are poorly preserved where they occur at the surface (Rawling et al., in review) and although their occurrence is documented in the subsurface (Attig 1985 and 1993; Woodruff et al., 2004), their regional distribution is poorly documented. During the most recent glaciations, ice flowed from the northeast through the Superior Basin until it was thick enough to spill over the regional bedrock divide (Attig and Rawling, 2018). Ice formed during an earlier glaciation deposited glacial and meltwater sediment of the River Falls Formation (Syverson, 2007). River Falls tills and outwash are preserved on uplands in the Eau Claire area, and landforms associated with this advance have been eroded and are not preserved. The best preservation of landforms is associated with the late Wisconsinan ice (ca. 25–11.5 yr B.P.), which formed the Chippewa Lobe that reached its maximum extent at the Chippewa Moraine. This ice was subject to stagnation whenever the ice profile in the Superior Basin lowered, resulting in an ice margin landscape consisting of broad (10s of kilometers) zones of stagnant ice features such as disintegration ridges, ice-walled lakes, and kettles. Figure 1. Top: Map of Wisconsin showing areas covered by lobes of the southern Laurentide Ice Sheet during the late Wisconsinan (MIS-2) Glaciation; inset map shows distribution of ice in the Great Lakes region. The red circle shows the location of Eau Claire near the southern edge of Chippewa Lobe. Bottom: Schematic illustration showing how moraines form over time. Supraglacial sediment accumulates at a stable ice margin (time one). As glacier retreats, buried ice is preserved under supraglacial sediment and minor moraines form if margin temporarily stabilizes (time two). The distribution of moraines after ice has melted (time three; modified from Attig and Rawling, 2018). 73 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Fluvial Landscapes The process of knickzone migration and incision up the LCR was episodic and unexpectedly prolonged. The episodic history of knickzone migration and incision is clearly indicated by the number and spatial distribution of terraces found in the LCR valley below the Wissota. Instead of two terrace levels resulting from the two episodes of abrupt base-level fall, there are as many as seven (Fig. 2). Each of these levels represents a period when the river was migrating laterally and forming a floodplain, followed by an episode of renewed incision that left the floodplain as a terrace. The prolonged history of knickzone migration and incision along the LCR is revealed by the optically stimulated luminescence (OSL) ages of terrace alluvium from several sites in the LCR valley (Fig. 3). These OSL ages indicate that knickzone migration took thousands of years longer than studies of modern alluvial streams affected by minor base-level falls suggest it should’ve taken (Begin 1986, 1988; Begin et al., 1981) The Chippewa River is the second largest stream in Wisconsin, draining a watershed of approximately 25,000 km2 to the upper Mississippi River (UMR). During the Late Wisconsinan, it was the primary stream draining meltwater from the Chippewa Lobe. Overloaded with glacigenic sediment, the lower Chippewa River (or LCR, which refers to the river beyond the Chippewa Moraine) filled its bedrock valley with sandy outwash to depths exceeding 50 meters. Then, sometime between 18-16 ka, the UMR incised 15 m, and at ~13.4 ka, it incised an additional 40 m (Knox 2007; Loope 2012; Gran et al. 2013). Each of these incision episodes abruptly lowered the base level of the LCR, creating knickzones that migrated up the LCR and its tributaries. The incision resulting from knickzone migration created the Wissota terrace, a prominent landform in the LCR valley that marks the maximum height of LCR aggradation during the Late Wisconsinan (Andrews 1965). Figure 2. Terraces of the LCR valley. The names of terraces below the Wissota terrace are based on their height above the modern floodplain and distance below the Wissota. From lowest to highest these are T-1, T-2, T-3, T-4, T-5, and T-6. One terrace that does not fit into the T1-T6 schema is found in the relatively narrow bedrock valley downstream from the Eau Galle-Chippewa River confluence. Named the Maxville Terrace, this terrace slopes from the level of the Wissota at its upvalley end to a level equivalent to T-4 in the UMR valley. (Figure from Faulkner et al. (2016).) 74 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 3. A proposed model of the evolution of the longitudinal profile of the LCR in response to UMR incision labeled with OSL ages of terrace alluvium. The profiles were constructed by connecting scattered terrace remnants, except for the Wissota and Maxville terraces, which are relatively continuous features. (Modified from Faulkner et al. (2016).) Autogenic variations in the amount of sediment supplied to the river likely explain why the migration of knickzones and incision up the LCR was episodic and prolonged. Incision resulting from knickzone migration would’ve created a relatively deep narrow channel with steep, unstable banks. Bank collapse, promoted by lateral stream erosion, would have greatly increased the supply of sediment to the stream. With more sediment to transport, the stream would no longer have had excess power, causing knickpoint migration and incision to slow or cease altogether. This, in turn, would’ve allowed lateral stream migration and floodplain formation to occur. Over time, lateral erosion and bank failure would’ve caused the banks to move away from the stream and become less steep, leading to a reduction in the amount of sediment supplied from them to the LCR. With a declining sediment supply, the stream would’ve once again had excess power, resulting in renewed knickzone migration and incision, at least until the process repeated itself farther upstream. The supply of sediment to the LCR from its tributaries was also subject to autogenic variations. LCR incision resulting would have lowered base level for its tributary streams, creating knickzones that then migrated up them. The subsequent tributary incision would have caused a dramatic increase in the supply of sediment to the LCR. Sediment supplied from tributaries would have remained high until their incised channel banks began to stabilize. But until that happened, high amounts of tributary sediment would have affected knickpoint migration and incision on the LCR, slowing it down and possibly causing it to stop. It is likely that autogenic variations in sediment from the largest tributaries, the Red Cedar River and the Eau Claire River, had the biggest impact on the LCR. Aeolian Landscapes There is abundant evidence throughout the Eau Claire region that wind has been a significant geomorphic agent during the late Quaternary. The most widespread evidence of aeolian activity is provided by deposits of loess, which were mainly sourced from the outwash plains of meltwater streams, including that of the Chippewa River (Schaetzl et al., 2014; Schaetzl et al., 2018; Fig. 4). Loess deposition during the Late Wisconsinan in the Eau Claire region began no later than 24 ka and continued until as recently as 10 ka (Schaetzl et al., 2014). Over this interval, the dominant processes of loess transport and deposition 75 �Proceedings of the 69th ILSG Annual Meeting - Part 2 2014). Later, strong northwest winds entrained sands from outwash and weathered sandstone. As they traveled over existing loess, saltating sands remobilized it and kept it in suspension until topographic barriers blocked further sand movement, which allowed loess to accumulate in their lee. Today, large swaths of the region are loess-free, with the thickest loess found on the southeast sides of prominent sandstone inselbergs and ridges (Schaetzl et al., 2018). A variety of sandy aeolian landforms, such as parabolic dunes, sand sheets, sand ramps, and sand stringers, also attest to the geomorphic significance of wind in the Eau Claire region. While these landforms are generally subtle and apparent only on LiDAR-derived DEMs, they are widespread (Fig. 5). They also have a generally consistent orientation, which indicates that they were primarily formed by west-northwesterly winds. In addition, a dozen OSL ages from different landforms reveal that sandy aeolian landforms in the region were being deposited between 13 and 9 ka (Schaetzl et al., 2018; Millett, 2019; Mataitis, 2020; Shandonay et al., 2022). Figure 4: Extent and thickness of loess within in western Wisconsin, as derived from Natural Resources Conservation Service county soil surveys (from Schaetzl et al., 2018.) apparently changed (Schaetzl et al., 2018). Existing evidence indicates that, early on, loess was primarily deflated from the outwash plains of the Chippewa River and its meltwater tributaries and deposited downwind of them (Schaetzl et al., Figure 5. Parabolic dunes (Millett, 2019) and sand stringers (Schaetzl et al., 2018; Mataitis, 2020) identified from lidar-derived DEMs, aerial photographs, and soil survey data in and near the LCR valley. 76 �Proceedings of the 69th ILSG Annual Meeting - Part 2 buried and melted. The dominant landforms in the area are ice-walled lake plains (Figs. 6 and 7; Clayton et al., 2001), such as the one the Obey Center is built upon. These form when lakes develop in the stagnant ice landscape preserved in permafrost conditions. It is likely that permafrost conditions were in northern Wisconsin until ~13.5 ka (Attig and Rawling, 2018; Batchelor, 2019). They are composed of laminated finegrained sediment that is typically fine sand and silt. These landscapes contain organic material further south that have aided in interpreting the timing of the Lake Michigan Lobe (Curry et al., 2018); however, organic material is typically not preserved in northern Wisconsin. Field Trip Stops UTM coordinates are in zone 15, WGS84 datum Stop 1: Copper Falls Glacial Deposits UTM coordinates 623464E, 5008658N Till of the Copper Falls Formation is reddish brown, sandy (~30 – 80% sand; Syverson, 2007; Syverson et al, 2011), and sourced from the northeast. Copper Falls till is distinguished from older River Falls till primarily by the landscape they underlie. Copper Falls sediment is found in relatively unmodified landscapes formed during the late Wisconsinan. Glacial landforms (moraines, eskers, drumlins, ice-walled lake plains…) are well persevered. River Falls sediment is associated with a highly eroded landscapes and likely formed before the late Wisconsinan Glaciation. This roadcut exposes typical unsorted glacial deposits of the Copper Falls Formation deposited as stagnant ice melted. Stop 2. David R. Obey Ice Age Interpretive Center UTM coordinates 624514E, 5009009N The interpretive center is located in the Chippewa Moraine State Recreation Area and within the Chippewa Moraine. The moraine formed when late Wisconsin ice was at its maximum position (Syverson, 2007). The landscape here is generally described as hummocky, and formed as stagnant ice was Figure 6. Schematic illustration showing the formation of ice walled lake plains (from Clayton et al., 2001). (A) Supraglacial sediment forms at the surface of stagnant ice and lakes occupies low areas where sorted sediment accumulates. (B) Hummocky topography with ice-walled lake plains remain after the ice has melted. Figure 7. Lidar-derived DEM showing the hummocky topography of the Chippewa Moraine near Stops 1 and 2. Ice walled lake plains are abundant within the moraine, which contrasts with the flat landscape formed by meltwater streams (outwash). 77 �Proceedings of the 69th ILSG Annual Meeting - Part 2 suggest that it happened during the late Holocene (Fig. 3). Stop 3. Colluvium Exposure UTM coordinates 625123E, 5001761 N The falls consist of a series of small knickpoints formed in early Proterozoic bedrock consisting of banded amphibolites with granitic intrusions (Myers and Maercklein, 1978). The angular form of the knickpoints, along with angular boulders of the same lithology scattered along the channel bed, suggest that the river is incising here primarily by mean of hydraulic plucking. Hydraulic plucking occurs when flows are deep and fast, leading to a zone of flow separation and low pressure on the downstream face of knickpoints. If the bedrock of a knickpoint is sufficiently jointed and weathered, the resulting drag force will pull blocks away from the knickpoint face. Polished rock surfaces with rare grooves and potholes indicate that abrasion by bedload sediment is also playing a role here in channel incision, although its effects appear secondary to that of plucking. The landscape beyond the LIS margin was greatly affected by periglacial processes. One of the most profound effects was the stripping of hillslopes by the mass-wasting process of solifluction (Clayton et al., 2001). Evidence of solifluction is provided by relict deposits of colluvium (colluvial aprons) that mantle bedrock slopes in areas of former permafrost. Here we see a prime example of such a colluvial deposit, which consists of an unsorted mixture of sandstone clasts (pebble to boulder in size) supported in a matrix of silty sand. The sand and the sandstone clasts were likely derived from the underlying bedrock (sandstone of the Cambrian Eau Claire Formation) by intense freeze-thaw weathering during the Late Wisconsinan. The silty material probably is loess that winds deflated and transported to the sight from nearby outwash plains. While the Chippewa has clearly incised into the Jim Falls bedrock, incision overall has been minimal. The lack of incision is likely due, in part, to the weathering and erosion-resistant nature of the bedrock. An additional factor is the relatively short amount of time that the river has been incising at this location. Given the model of long-profile evolution in Figure 3, incision didn’t start here until sometime after 4.7 ka. Stop 4. Jim Falls UTM coordinates 635875E, 4990538 N) The Chippewa at Jim Falls is an example of a superimposed river (Fig. 8). Here, the Chippewa River incised through a cover of outwash and till and encountered a topographic high in the buried a bedrock landscape. It did not, however, incise to its present level in one episode of downcutting, as evidenced by two terraces that are apparent at and near this site. The highest terrace grades to the Wissota terrace, the maximum level of aggradation of the lower Chippewa River. This indicates that the river continued to flow at this level after the glacial margin had retreated to the north of this site. Remnants of a terrace approximately 3 meters below the Wissota (best seen downstream from the east end of the pedestrian bridge), which is cut into till, indicate a period of channel stability before the river incised further to the buried bedrock. When deeper incision occurred is unknown, although OSL ages of terrace alluvium farther down valley The site today clearly is highly modified by a dam, appropriately named the Jim Falls Dam. The original Jim Falls Dam was built in 1923 to utilize the hydraulic head provided by the falls to generate electricity. It was designed so that the falls were bypassed and left dry except during high flows, when excess water was released through a spillway that was located at the falls upstream end. The dam was redeveloped in 1988 and now has the highest generation capacity of any hydropower dam in Wisconsin (~60 MW). This redevelopment included moving the main spillway from the head of the falls to a location adjacent to a new main powerhouse. It also included constructing a smaller spillway and 78 �Proceedings of the 69th ILSG Annual Meeting - Part 2 auxiliary powerhouse where the main spillway had been. This was done so that a minimum flow of 240 cfs could be released down the bypassed reach year-round, except for the period April 1- May 31, when flow through the reach is increased to 850 cfs to enhance fish spawning habitat. Figure 8. Lidar-derived DEM of Jim Falls and surrounding area. Stop 5. Wildenberg Quarry Evidence for permafrost during the Late Wisconsinan is widespread in Wisconsin, with a hypothesized permafrost interval in central Wisconsin from ca. 33 to 15 ka (Batchelor et al., 2019) and as late as 13.5 ka in northern Wisconsin (Attig and Rawling, 2018). This interval is, however, poorly constrained in the Eau Claire region due to a lack of 14C datable materials in features diagnostic of permafrost. OSL dating now makes it possible to date proxy geomorphic features, like ice-wedge pseudomorphs, to help constrain this (Schaetzl et al., 2021). UTM coordinates 616648 E, 4970372 N Note: This is private property. No access is allowed without owner’s permission. Glacial sediment of the River Falls Formation includes till that is lithologically like the Copper Falls Formation and melt-water stream sediment (Syverson, 2007; Severson et al., 2011). These can be distinguished from the Copper Falls formation because they occur at the top of highly eroded landscapes and the soils in them are more developed. There are no primary glacial landforms associated with the River Falls Formation, likely due to intense modification by periglacial processes in permafrost conditions during the late Wisconsinan. The ice-wedge pseudomorphs in this quarry are sand wedges (Fig. 9). Sand wedges such as these form in periglacial settings when thermal contraction of frozen ground in winter forms 79 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 9. Sand wedges exposed in the headwall of the Wildenberg quarry in July 2018. (Photograph by Randy Schaetzl.) cracks in the soil. If this happens in a cold, dry, wind-swept environment with sand available for transport, sand will blow into and fill the cracks. Over time, repeated cracking and filling will form vertical structures that generally taper with depth. OSL dating of sand wedges in this quarry and in another quarry located 60 km to the south indicate that thermal contraction cracks existed and were filling with sand from no later than 19.3 ka until 14.7 ka. Schaetzl et al. (2021) interpret these ages as documenting when permafrost in the region most likely ended. Interestingly, the OSL ages from this quarry (15.1 and 14.7 ka) are younger than those from the quarry 60 km to the south (19.3, 19.1, and 18.3 ka). These may represent a time-transgressive spatial relationship in that permafrost possibly degraded earlier at the more southerly location and remained longer at the more northerly one, although this is purely speculative given the large errors on the OSL ages (1.4 to 2.2 ka at 1). That said, the larger and more complex morphologies of the sand-wedges found at this quarry do suggest the possibility of more intense sand-wedge development due to more prolonged permafrost conditions. City incorporated it into its bicycle-pedestrian trail system. In addition to being historically significant, the High Bridge (Fig. 10) affords an excellent view of many of the terrace levels found in the LCR valley. The High Bridge itself is at the level of T6. To the east, trees and houses can be seen at the top of the Wissota terrace scarp, which is 6-7 meters above T-6. The Wissota can also be seen to the west where the pedestrian-bicycle trail cuts into its scarp. Looking downstream, lower terraces are difficult to discern from this vantage point, although the residential and business districts located near the river provide clues. These built-up areas are all above the 100-year flood level. That is, they all are on terraces. In Eau Claire, there is little active floodplain. This suggests that incision below the lowest terrace level occurred here recently (within the last 2.3 ka according to the model of long-profile evolution in Fig. 3). Upstream from the High Bridge is the Dells Dam. This dam, which was built in 1924 for the purpose of generating electricity, is situated at an unusually good site for a dam on the LCR – a bedrock gorge. This gorge was formed when the river incised into a cover of glacial outwash that buried a low ridge of Cambrian sandstone (Mt. Simon Formation) connecting Mt. Simon (the conical bedrock hill located approximately 500 m northeast of the dam) to the bedrock uplands located west-northwest of it. In other words, the river here did not incise into its pre-glacial bedrock valley, which is located east of Mt. Stop 6. High Bridge UTM coordinates 617832E, 4964561N This stop is on the so-called High Bridge in the city of Eau Claire. Standing 26 m above the Chippewa River, the High Bridge was built in 1880 as a railroad bridge and was an innovative bridge for its time. It was abandoned in 1992, and the City acquired ownership in 2007. In 2015, the 80 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Simon and the High Bridge. This is an example of an epigenetic gorge (Ouimet et al., 2008), and the river likely carved it sometime after 7.4 ka (see Fig. 3). Incision is actually still occurring here, as evidenced by a 1.5-m bedrock knickpoint located 180 m downstream of the bridge. Figure 10. Lidar-derived DEM showing the stream terraces found in Eau Claire in the vicinity of the High Bridge. upvalley and on the valley’s other side. The last episode of incision, below T-1, occurred within the last 2.3 ka based on an OSL date of T-1 fill from a site also located 6.5 km upvalley (Fig. 3). In the downstream direction, the valley below the Wissota is predominantly floodplain with only rare lower terrace remnants. In addition, the river’s planform switches from a single-thread meandering shape to a multi-thread anabranching one that extends downvalley for a distance of 8.5 km. At that point, it returns to a single-channel meandering form. It is uncertain why this anabranching reach exists, although its similarity to the sedimentation zones of wandering gravel bed streams in British Columbia described by Desloges and Church (1987) suggests a cause. Given its location immediately downstream of Stop 7. Sand Hill Cemetery UTM coordinates 599549E, 4958254N This stop is at the edge of the Wissota terrace tread and top of the Wissota terrace scarp. To the north, a braided channel is apparent in the subtle rolling topography of the Wissota tread, providing evidence of the Chippewa’s glacial past (Fig. 11). To the south, the Wissota scarp descends nearly 30 m to the lowest terrace in the valley (T-1). Looking upvalley, this terrace can be identified by the farmland situated on it. Lowlying land that is wooded is either floodplain or paleochannels cutting across the T-1 surface. Incision here below the Wissota level occurred between 10 and 9 ka, based on four OSL dates of Wissota fill obtained from sites located 6.5 km 81 �Proceedings of the 69th ILSG Annual Meeting - Part 2 the reach that was recently incised below T-1, it could be the result of sedimentation resulting from that incision event (Fig. 12). A pronounced convexity in the long profile of the modern river along the anabranching reach supports this hypothesis (Faulkner et al., 2016). Figure 11. Lidar-derived DEM showing the fluvial and aeolian landforms in the vicinity of the Sand Hill Cemetery (Stop 7), which are discussed in the text. Figure 12. Cartoon showing the setting of the anabranching reach (and hypothesized sedimentation zone) downstream of the reach that is incised below the T-1 terrace (adapted from Adams et al., 2016). 82 �Proceedings of the 69th ILSG Annual Meeting - Part 2 A short distance (~200 m) west of the Sand Hill Cemetery, an elongate wooded hill—informally named the Steffes-Zanoni site—can be seen rising above the low-relief landscape of the Wissota terrace. (This hill can also be seen in Fig. 11.) Its summit is approximately 8 m higher than the surrounding Wissota terrace surface, and its elongate form runs parallels to the Wissota terrace scarp. The landform is composed of sand that is mineralogically indistinguishable from the terrace sediments beneath it, although it is relatively finer-grained and more well-sorted, indicating that it is aeolian sand (Millett, 2019). It is also morphologically complex, consisting of multiple parabolic forms coalesced together with smaller parabolic forms on top of them. These forms--smaller parabolic dunes superimposed on larger older ones—indicate repeated aeolian activity at this site. The OSL ages of samples obtained from depths of 1.7 m and 2.5 m near the hill’s northwest end suggest a depositional age of the landform’s upper part to be ~0.5 ka. Larson et al. (2008) identified a dune similar to this one in the city of Eau Claire and called it a cliff-top parabolic dune (because of its form and its proximal relationship to the Wissota terrace scarp). Since then, many cliff-top parabolic dunes have been noted in the Eau Claire region (note the large number of parabolic dunes situated along the Wissota scarp in Fig. 5). Why these dunes exist will be discussed at our final stop. with parabolic forms oriented perpendicular to them—are hypothesized to have had a similar genetic origin (Larson et al., 2008; Millett, 2019). In their proposed model, a river cuts into the base of a high fill-terrace scarp. This creates an unstable cutbank and promotes mass wasting that removes vegetation from the scarp face. Wind that then blows against such a scarp gets compressed, which causes its velocity to go up. The increase in velocity enhances the wind’s ability to entrain exposed sandy sediment and transport it up the scarp face. When this happens, the sandy sediment ultimately settles out at the top of the scarp as wind velocity is reduced there. This leaves behind “cliff-top dunes.” (Fig. 14). Given this model of dune genesis, one should expect cliff-top dunes to have different orientations and depositional ages compared to other parabolic dunes not in cliff-top positions. This is indeed the case. Non-cliff-top dunes generally have a northwest-southeast orientation and depositional ages older than 10 ka. Cliff-top dunes display a variety of orientations (perpendicular to their scarps) and are generally much younger. OSL ages from a cliff-top dune in the city of Eau Claire indicate a period of aeolian deposition at ca. 6.0 ka, while two from the Steffes-Zanoni site (Stop 7) indicate that deposition in the uppermost dune sediments occurred at ca. 0.5 ka. At the Kiwanis site, eight OSL ages point to two depositional episodes: at ca. 0.9 ka and 0.5 ka. Stop 8. Town of Union Conservancy The model of Larson et al. (2008) of cliff-top dune genesis suggests that these should be forming wherever the Chippewa River is eroding laterally into Wissota terrace fill. This, however, is not the case; today, all cliff-top dunes in the LCR valley are stabilized by vegetation and no longer moving. Thus, the genesis of these landforms is doubtless more complex than the model of Larson et al. (2008) suggests, with climatic variability likely playing a key role in the process of aeolian sedimentation and dune formation at cliff-top locations (Millett, 2019). For example, during humid climate intervals UTM coordinates 607504E, 4959523N Note: This site involves walking on unpaved trails for an approximate distance of one mile. There are some short sections of the trail that are moderately steep. Parabolic dunes in cliff-top positions are especially prominent at this location, which is informally called the Kiwanis Site (Fig. 13). Like those seen at the previous stop, these dunes are situated atop the Wissota terrace scarp. These dunes and others that are similarly situated in the LCR valley—above high Wissota terrace scarps 83 �Proceedings of the 69th ILSG Annual Meeting - Part 2 (such as at the present), high cutbanks carved by the river into Wissota fill are colonized readily by vegetation, which inhibits the entrainment and transport of sand up terrace scarps. In contrast, during arid intervals, vegetation cover is greatly reduced, especially on steep well-drained terrace scarps, allowing wind to entrain and transport sand up them. OSL ages from the Kiwanis Site and the Steffes-Zanoni Site support the significance of climate variability in the formation of cliff-top dune. At Kiwanis, these ages indicate two pulses of aeolian deposition – the first at ca. 0.9 ka and a second at ca. 0.5 ka, with the latter coinciding with ages from the Steffes-Zanoni Site. If correct, these pulses happened during the Medieval Climatic Anomaly when well documented dry periods affected the mid-continent of North America (reviewed in Millett, 2019). forms enclosed by a subtle linear ridge appear to be anthropogenic features. It is likely, based onthe morphology and distribution of these features, that their creation was tied to the genesis of the prominent aeolian dunes found nearby and, potentially, culturally linked to a wellestablished late Woodland period of mound building in the upper Mississippi River valley – a period which would have coincided with the formation of the Kiwanis and Steffes-Zanoni dunes. Based on the configuration of these features, it is hypothesized that this site represents the “Thunderer,” an effigy of a bird-like deity, or sky being. The spotted Thunderer, with “spots” represented by the location of the mounds within the linear structure, is associated with the West and the bringer of storms. If true, Native peoples may have watched the dunes form during a period of more aridity during episodes of higher winds/storms, resulting in this site being spiritually significant at that time and now an important site of cultural heritage (R. Schirmer, personal communication). Lastly, closer examination of the Kiwanis Site (Fig. 13) reveals landforms in close proximity to the dunes that do not look to be of natural origin. Several hemispherical (or conical) mound-like Figure 13. The Kiwanis Site. Cliff-top parabolic dunes are situated directly above the Chippewa River on top of the Wissota terrace scarp. Also note the hemispherical mounds and linear ridge of hypothesized anthropogenic origin. 84 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Figure 14. Model of cliff-top dune genesis induced by lateral river erosion (adapted from Larson et al., 2008). Begin, Z.B. 1986. Determination of “diffusion” erosion coefficients for some tributaries of Oaklimiter Creek, North-Central Mississippi, in Hadley, R.F., ed., Drainage Basin Sediment Delivery. IAHS Publication, p. 447–462. References Adams, H.R., Vincent, A.M., and Faulkner, D.J. 2016. Patterns of downstream fining on the lower Chippewa River, Wisconsin: Abstracts, Annual Meeting - American Association of Geographers, San Francisco, CA Begin, Z.B. 1988. Application of a diffusion-erosion model to alluvial channels which degrade due to base-level lowering: Earth Surface Processes and Landforms, v. 13, p. 487–500. Andrews, G.W. 1965. Late Quaternary geologic history of the Lower Chippewa Valley, Wisconsin. Geological Society of America Bulletin: v. 76, p. 113–124. Begin, Z.B., Meyer, D.F., and Schumm, S.A. 1981. Development of longitudinal profiles of alluvial channels in response to base-level lowering: Earth Surface Processes and Landforms, v. 6, p. 49–68. Attig, J.W. 1985. Pleistocene Geology of Vilas County, Wisconsin: Wisconsin Geological and Natural History Survey, Information Circular 51, 32 p. Clayton, L., Attig, J.W., and Mickelson, D.M. 2001. Effects of late Pleistocene permafrost on the landscape of Wisconsin: Boreas, v. 30, p. 173–188. Attig, J.W. 1993. Pleistocene Geology of Taylor County, Wisconsin: Wisconsin Geological and natural History Survey, Bulletin 90, 25 p. Curry, B.B., Lowell, T.V., Wang, H., and Anderson, A.C. 2018. Revised time-distance diagram for the Lake Michigan Lobe, Michigan Subepisode, Wisconsin Episode, Illinois, USA, in Kehew, A., and Curry, B.B., eds., Quaternary Glaciation of the Great Lakes Region: Process, Landforms, Sediments, and Chronology: Geological Society of America Special Paper 530, p. 1–12. Attig, J.W., and Rawling, J.E., III. 2018. Influence of persistent buried ice on late glacial landscape development in part of Wisconsin’s Northern Highlands, in Kehew, A., and Curry, B.B., eds., Quaternary Glaciation of the Great Lakes Region: Process, Landforms, Sediments, and Chronology: Geological Society of America Special Paper 530, p. 1–12. Desloges, J.R., and Church, M. 1987. Channel and floodplain facies in a wandering gravel-bed river, in Ethridge, F.G., Flores, R.M., Harvey, M.D., Weaver, J.N., eds., Recent Developments in Fluvial Sedimentology: Special Publication. Society of Economic Paleontologists and Mineralogists, p. 99–109. Batchelor, C.J., Orland, I.J., Marcott, S.A., Slaughter, R., Edwards, R.L., Zhang, P., Li, X., and Cheng, H. 2019. Distinct permafrost conditions across the last two glacial periods in midlatitude North America: Geophysical Research Letters, v. 46, no. 22, p. 13318-13326. 85 �Proceedings of the 69th ILSG Annual Meeting - Part 2 Faulkner, D.J., Larson, P.H., Jol, H.M., Running, G.L., Loope, H.M., and Goble, R.J. 2016. Autogenic incision and terrace formation resulting from abrupt late-glacial base-level fall, lower Chippewa River, Wisconsin, USA: Geomorphology, v. 266, p. 75–95. Schaetzl, R.J., Forman, S.L., and Attig, J.W. 2014. Optical ages on loess derived from outwash surfaces constrain the advance of the Laurentide Ice Sheet out of the Lake Superior Basin, USA: Quaternary Research, v. 81, p. 318–329. Schaetzl, R.J., Larson, P.H., Faulkner, D.J., Running, G.L., Jol, H.M., and Rittenour, T.M. 2018. Eolian sand and loess deposits indicate west-northwest paleowinds during the Late Pleistocene in western Wisconsin, USA: Quaternary Research, v. 89, p. 769–785. Gran, K.B., Finnegan, N., Johnson, A.L., Belmont, P., Wittkop, C., and Rittenour, T. 2013. Landscape evolution, valley excavation, and terrace development following abrupt postglacial baselevel fall: Geological Society of America Bulletin, v. 125, p. 1851–1864. Schaetzl, R.J., Running, G.L., Larson, P., Rittenour, T., Yansa, C., and Faulkner, D. 2022. Luminescence dating of sand wedges constrains the Late Wisconsin (MIS 2) permafrost interval in the upper Midwest, USA: Boreas, v. 51, p. 385– 401. Knox, J.C., 2007. The Mississippi River System, in Gupta, A., ed., Large Rivers: Geomorphology and Management. John Wiley & Sons, Chichester, England ; Hoboken, NJ, p. 145–182. Larson, P.H. McDonald, J., Baker, A., Dryer, W.P., Running, G.L., Faulkner, D.J. and Jol, H.M. 2008. Geomorphology of cliff-top parabolic dunes within the lower Chippewa River valley, upper Putnam Park, Eau Claire, Wisconsin: Abstracts, Annual Meeting - Association of American Geographers, Boston, MA. Schirmer, R. 2023. Personal communication regarding archeology in the upper Mississippi valley and the Kiwanis Site. 3/8/2023. Shandonay, K.L., Bowen, M.W., Larson, P.H., Running, G.L., Rittenour, T., and Mataitis, R. 2022. Morphology and stratigraphy of aeolian sand stringers in southeast Minnesota and western Wisconsin, USA: Earth Surface Processes and Landforms, v. 47, p. 2863–2876. Loope, H.M., Mason, J.A., Knox, J.C., Goble, R.J., Hanson, P.R., Young, A.R., and Curry, B.B. 2012. Late Wisconsinan aggradation and incision history of the upper Mississippi River, USA: Abstracts with Programs - Geological Society of America, v. 44, p. 455. Syverson, K.M. 2007. Pleistocene Geology of Chippewa County, Wisconsin: Wisconsin Geological and natural History Survey, Bulletin 103, 53 p. Mataitis, R. 2020. “Geomorphology and chronology of sand stringer deposition beyond the ice margin: Southeastern Minnesota and western Wisconsin, USA.” M.S. Thesis. Minnesota State University, Mankato. Syverson, K.M., Clayton, L., Attig, J.W., and Mickelson, D.M. 2011. Lexicon of Pleistocene Stratigraphic Units of Wisconsin: Wisconsin Geological and Natural History Survey Technical Report 1, 180 p. Millett, J. 2019. “Cliff-top dunes in the lower Chippewa River valley of west-central Wisconsin.” M.S. Thesis. Minnesota State University, Mankato. Woodruff, L.G., Attig, J.W., and Cannon, W.F. 2004. Geochemistry of glacial sediments in the area of the Bend massive sulfide deposit, north-central Wisconsin: Journal of Geochemical Exploration, v. 82, p. 97–109. Myers, P.E., and Maercklein, D.A. 1978. Amphibolites and Granites at Jim Falls: Wisconsin Geology of Wisconsin – Outcrop Descriptions, Geological and Natural History Survey, 7 p. Rawling III, J.E., Carson, E.C., Attig, J.W., Mickelson, D.M., Mode, W.N., Johnson, M.D., Syverson, KM. (in preparation). The Quaternary Geology of Wisconsin. Wisconsin Geological and Natural History Survey. Map Sale 1:500,000. 86 � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 2023 Description An account of the resource Institute on Lake Superior Geology. Eau Claire, Wisconsin. April 24-25, 2023. Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 2023-04-24 Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English Type The nature or genre of the resource Text https://digitalcollections.lakeheadu.ca/files/original/0b24745b5f54dab200df24eadc001ccf.pdf b70185d5c567dae0da9dc29359c01222 PDF Text Text ���������������������������������������������������������������������� Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University Alumni Collection Description An account of the resource Material kept by the Lakehead University Alumni Association, or donated by Alumni to the Association. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Intramural and Varsity Athletic Banquet, 1979-1980 Subject The topic of the resource Universities Description An account of the resource The book contains sports award recipients, team rosters, and team standings and statistics, records and highlights from the 1979-1980 intramural and varsity sports season. The banquet was held at the DaVinci Centre on April 3rd, 1980. Creator An entity primarily responsible for making the resource Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 1980-04-03 Language A language of the resource English 1980 1980s intramural sports Lakehead athletics Nor'Wester student committee on athletics varsity athletics https://digitalcollections.lakeheadu.ca/files/original/63f433e29dc33d217f1c22a1efcdf2d1.pdf 8df9d5ae3162df515453ed084cbdf99c PDF Text Text �������� Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University Alumni Collection Description An account of the resource Material kept by the Lakehead University Alumni Association, or donated by Alumni to the Association. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University Nor'Westers Basketball Program for Women's and Men's games on Jan 5/6, 1990 Subject The topic of the resource Universities Description An account of the resource Booklet contains January 1990 varsity basketball home schedule and Lakehead women's and men's basketball team rosters. It also contains the team rosters of the opponents teams. Creator An entity primarily responsible for making the resource Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 1990-01 Language A language of the resource English 1990 Baseball Basketball team Men's Basketball roster varsity varsity athletics Women's Basketball https://digitalcollections.lakeheadu.ca/files/original/987933bdc82efa1b8d0adc46782be62a.pdf 32ef89cf6b2030a66c0ea44d210a567d PDF Text Text ������������������������������������������������������������������������ Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University Alumni Collection Description An account of the resource Material kept by the Lakehead University Alumni Association, or donated by Alumni to the Association. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Nor'Westers P.E. Yearbook 1990-1991 Subject The topic of the resource Universities Description An account of the resource Physical Education yearbook for the year 1990-1991. Contains class photos and names by year, photos and memories from the school year and professor information. Creator An entity primarily responsible for making the resource Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 1991 Language A language of the resource English 1990 1991 Alumni Lakehead Lakehead Alumni Lakehead athletics Nor'Wester Physical Education Yearbook https://digitalcollections.lakeheadu.ca/files/original/d7ad9738f90c0ed88a4faa04e0df1aa0.pdf 705d1d089bee8a6a7115b7702e9b8fb5 PDF Text Text �������������������������������������������������������������� Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University Alumni Collection Description An account of the resource Material kept by the Lakehead University Alumni Association, or donated by Alumni to the Association. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Nor'Westers P.E. Yearbook 1989-1990 Subject The topic of the resource Universities Description An account of the resource Physical Education yearbook for the year 1989-1990. Contains class photos and names by year, photos and memories from the school year and professor information. Creator An entity primarily responsible for making the resource Lakehead Univeristy Date A point or period of time associated with an event in the lifecycle of the resource 1990 Language A language of the resource English Format The file format, physical medium, or dimensions of the resource PDF Type The nature or genre of the resource Text 1989 1990 Alumni Lakehead Alumni Lakehead athletics Nor'Wester Physical Education Yearbook https://digitalcollections.lakeheadu.ca/files/original/ef32259eaf2189a69443b03071bd82f0.pdf 1ae3c8c2761627421a10e96dd8eb4460 PDF Text Text �������������������������������������������������������������������������� Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University Alumni Collection Description An account of the resource Material kept by the Lakehead University Alumni Association, or donated by Alumni to the Association. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Lakehead University P.E. Yearbook, 1992 Subject The topic of the resource Universities Description An account of the resource Physical Education yearbook for the year 1991-1992. Contains class photos and names by year, photos and memories from the school year and professor information. Creator An entity primarily responsible for making the resource Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 1992 Language A language of the resource English Format The file format, physical medium, or dimensions of the resource PDF Type The nature or genre of the resource Text 1991 1992 Alumni Lakehead Alumni Lakehead athletics Physical Education Yearbook https://digitalcollections.lakeheadu.ca/files/original/9a5668dcfc36bc3b5a8ac42d479c940b.jpg 45a8ad5aad013be5bc55ecdda515d3c3 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Thunder Bay Finnish Canadian Historical Society Collection Subject The topic of the resource Finnish-Canadians Life in Thunder Bay Description An account of the resource Photographs collected by the Thunder Bay Finnish Canadian Historical Society from a wide range of collectors, documenting Finnish immigration to and life in Thunder Bay. Creator An entity primarily responsible for making the resource Thunder Bay Finnish Canadian Historical Society Publisher An entity responsible for making the resource available Lakehead University Library Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Trappers with dog team Subject The topic of the resource Communities in Northwestern Ontario People Description An account of the resource Trappers with dog team, Nipigon, Ontario. People in photo: Joe Sault. Format The file format, physical medium, or dimensions of the resource JPG Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context MG8_D13Ei74 Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Canada - Ontario - Nipigon https://digitalcollections.lakeheadu.ca/files/original/c3fe0a1e52a261700eb333fd639b6b4a.jpg 8ad9f6e0c9fb2b930c52cae7d0d619cd Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Thunder Bay Finnish Canadian Historical Society Collection Subject The topic of the resource Finnish-Canadians Life in Thunder Bay Description An account of the resource Photographs collected by the Thunder Bay Finnish Canadian Historical Society from a wide range of collectors, documenting Finnish immigration to and life in Thunder Bay. Creator An entity primarily responsible for making the resource Thunder Bay Finnish Canadian Historical Society Publisher An entity responsible for making the resource available Lakehead University Library Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Beginnings of the "Boom" Description An account of the resource Beginnings of the "Boom" in Beardmore, Ontario, September, 1933. Home of Mr. & Mrs. Perala (left), construction of hotel, log structure (right). Date A point or period of time associated with an event in the lifecycle of the resource 1933-09 Format The file format, physical medium, or dimensions of the resource JPG Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context MG8_D13Ei75 Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Canada - Ontario - Beardmore Subject The topic of the resource Business and Industry Communities in Northwestern Ontario Rights Information about rights held in and over the resource Public domain