The Great Lakes Geologic Mapping Coalition—Working collaboratively to understand the geology of the Great Lakes Region

Lopez, Brianna-, Shelton, Jenna L.-, Marketti, Michaelmmarketti@usgs.gov, Ritzel, Kate- · 2026 · Report

Introduction The Great Lakes Geologic Mapping Coalition (GLGMC), commonly referred to as the “Coalition,” is a partnership between the U.S.

This 2026 document, The Great Lakes Geologic Mapping Coalition—Working collaboratively to understand the geology of the Great Lakes Region, is preserved in the Mountain Man Mining Library for research and reference. Original source: pubs.usgs.gov.

U.S. Department of the Interior U.S. Geological Survey Fact Sheet FS 2026-3010 May 2026 National Cooperative Geologic Mapping Program The Great Lakes Geologic Mapping Coalition— Working Collaboratively to Understand the Geology of the Great Lakes Region The Great Lakes Geologic Mapping Coalition (GLGMC), commonly referred to as the "Coalition," is a partnership between the U.S. Geological Survey (USGS); the U.S. States of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin; and the Canadian province of Ontario. The member States receive funding for geologic mapping work from the USGS National Cooperative Geologic Mapping Program (NCGMP), whereas Ontario participates as a nonfunded partner. The mission of the GLGMC is to produce three-dimensional (3D) geologic maps that depict unconsolidated sediments and near-surface bedrock in the Great Lakes region of North America. Geologic maps are the basis of most earth science investigations and help support resource exploration (energy, minerals, groundwater), natural hazard mitigation, infrastructure development, and land-use planning, all of which can be used to advance economic development and strengthen national security in the Great Lakes region. During the last few million years, the Great Lakes region has experienced repeated glacial advances and retreats, leaving behind extensive sediments, abundant natural resources, and widespread effects on the underlying bedrock geology (Swezey and others, 2022). Linked by shared histories of past glaciations, industrial agriculture, and legacy automotive, coal, steel, and manufacturing industries, the GLGMC member States collaborate to improve the understanding of the 3D distribution of the sediments overlying the region's bedrock (fig. 1). Developing a comprehensive subsurface 3D framework of this glaciated terrain can provide earth science data to policymakers at all levels. These insights facilitate informed decisions on the exploration, use, and protection of vital resources, such as critical minerals, industrial materials, and aquifers, thereby supporting economic prosperity and the well-being of the citizens of this region. Since its inception in 1998, the Coalition has completed more than 100 geologic mapping projects across the Great Lakes region. Each project aims to deliver geologic maps, 3D datasets, and other information that improves understanding of the geology of the Great Lakes region, with an emphasis on economic and water resources. Key deliverables include 3D geologic maps and models typically portraying sediment thickness, often derived from top-of-bedrock and borehole data. These products are developed through a combination of fieldwork, subsurface modeling, and the collection and analysis of rock and sediment cores. To support Coalition goals, member States collaborate with scientists working on related STATEMAP, EDMAP, and FEDMAP projects. Coalition scientists also engage with Tribal Nations in the Great Lakes region to ensure that Tribal interests pertaining to Coalition work are addressed. Through this collaboration, the Coalition unites the efforts of State, Federal, and Tribal Nation stakeholders to advance geologic data production and enhance understanding of the geologic resources of the Great Lakes region.

The NCGMP was created by the National Geologic Mapping Act of 1992 (Public Law 102-285). States recognized a need for a specialized coalition to study the glacial geology of the Great Lakes region. On December 17, the charter for the Central Great Lakes Geologic Mapping Coalition was signed between the USGS and the State geological surveys of Illinois, Indiana, Michigan, and Ohio. The Coalition expanded to include the State geological surveys of Minnesota, New York, Pennsylvania, and Wisconsin. The Coalition went international, including Canada as a nonfunded member that can benefit from and contribute to the science produced by the GLGMC member states.

Minnesota Geological Survey Quaternary Geologic Mapping The Minnesota Geological Survey (MGS) is carrying out a project called the County Geologic Atlas (CGA) program to support statewide groundwater management, mineral resource development, and civil engineering applications. As part of the CGA project, geologic mapping of surface and near-surface sediments relies on methods such as fieldwork, drilling, lithologic analyses, and geophysical surveys. With funding from the GLGMC, MGS staff analyze and correlate sediments in cores, which serve as benchmarks for cross sections (fig. 2) and geologic and groundwater models (fig. 3). The 1-kilometer cross sections, developed with GLGMC funding, help to identify and model subsurface sand bodies that may function as aquifers. Since 1995, the Minnesota Department of Natural Resources (DNR) has been partnering with the MGS on CGA reports. The geologic information provided in the MGS reports is used by the DNR to provide additional information on the groundwater conditions and contamination sensitivity of aquifers. Recently, the City of Motley in Cass County, Minnesota, used subsurface data from the MGS to identify a suitable location for a municipal water well. The data collected helped the city to save more than $700,000 in well-drilling costs (Barbara Lusardi, Minnesota Geological Survey, written commun., 2025). Additionally, MGS cross sections from the Washington County Geologic Atlas have been applied to groundwater flow modeling as part of remediation efforts addressing aquifer contamination. In addition to partnering with member States, the MGS collaborates with Tribal Nations to complete mutually beneficial geologic mapping. For example, the Red Lake Band of Chippewa Indians, Minnesota, granted MGS permission to drill on Tribal land in Koochiching County, Minnesota, to support subsurface modeling efforts. This work, along with similar subsurface projects across the state, provides information about sediments not exposed at the surface, enabling geologists to develop comprehensive subsurface models. The modeling completed in Koochiching County could help the Tribe to make informed landuse decisions with potential benefits to their community and the surrounding region. USGS Quaternary Geologic Mapping of the Glaciated Regions Project A team of USGS geologists collaborates with the GLGMC to interpret the geological framework of the glaciated region of the United States, with particular emphasis on the area surrounding the Great Lakes. The USGS Quaternary Geologic Mapping of the Glaciated Regions Project, referred to as the "Glaciated Regions Project," is currently (2026) focusing on detailed 1:24,000-scale Quaternary geologic mapping at Fort Drum in Jefferson and Lewis Counties, New York (fig. 4), and 1:100,000-scale geologic mapping in Dodge and Jefferson Counties, Wisconsin. The project addresses scientific challenges through innovative mapping approaches that provide societal and scientific benefits. Geological maps and associated products deliver data on aggregate (sand and gravel) resource potential, aquifer characteristics, groundwater contaminant pathways, sediment placer deposit potential for critical minerals, hazard potential for landslide and (or) slope failures, and improved delineation of the bedrock topography. Y T N U O S M A D A Y T N U O S E W ADAMS COUNTY JAY COUNTY WELLS COUNTY JAY COUNTY SCHEIDT RD E S E 1100 S E 800 N E 500 N WILSON RD E S E S E S W850 S E S S400 W WINKLER RD STRABLE RD S 000 RD E S E S N375 W S300 E W200 S COUNTYRD450 S W100 S W350 S W400 S W500 S E 1000 S N 200 E E S E 900 S W300 S W700 S E 350 S S650 W E S 300W W900 S E S W1150 S D R R E G R E B U A R G N250 W E S N650 W N550 W E N N 450 E 550 E E 600 N W1100 S E 500 S S 000 RD S 100 E E S S 300 E W950 S S200 W W500 N W500 N E 100 S E 100 S E 700 S E 700 S E 800 S E 800 S W650 N W650 N E 300 S E300 S E 400 S E 400 S E 200 S E 200 S D R M E A S S SSALEM RD 300W 300W W000 RD W1050 S COUNTYRD600 S Poling ytre bi tse W Phenix Perryville Domestic Coppess Corner Bryant Geneva Berne Monroe Willshire Y T N U O S M A D A Y T U O R E R E M A N A D N OHIO Y T N U O S M A D A Y T U O R E R E M A N A D N O H O -84°45'00" -84°47'30" -84°50'00" -84°52'30" -84°55'00" -84°57'30" -85°00'00" -85°02'30" -85°05'00" '30" -84°45'00" -84°47'30" -84°50'00" -84°52'30" -84°55'00" -84°57'30" -85°00'00" -85°02'30" -85°05'00" 30" 40°45'00" 40°42'30" 40°40'00" 40°37'30" 40°35'00" 40°32'30" 40°30'00" 40°45'00" 40°42'30" 40°40'00" Bedrock elevation (feet asl) Mississippi River U.S. Highway 2 Lake Winnibigoshish Foot Lake Middle Sucker Lake CSS-5 (276617) Pike Bay Elevation in feet above mean sea level Amv mi Amv Abd ups1 mt ml ups1 ebl3 et2 mlt3 sfs1 ebt2 ebt1 sft2 sft1 mlt2 sft1 sct brt1 mlt1 hsi2 hsa3 hsa4 hta3 hsa2 hta2 sc hsa3 hta2 sc hta1 hsa2 hti2 bds1 hti2 bds1 bdt2 bdt2 A A' 1,100 1,000 1,200 1,300 1,400 mt ebt2 sct mlt2 ebt2 ups1 Figure 1.  Detail from a bedrock elevation map generated during a joint investigation by the geological surveys of Indiana and Ohio (Rupp and others, 2021). Figure 2.  Cross section based on drill-hole and rotary-sonic core data depicting the distribution of unconsolidated sediments below the surface in Cass County, Minnesota (Lusardi and others, 2018).

The USGS works toward strengthening the Nation's resilience by applying its expertise in complex 3D glacial geology unique to the Great Lakes region, using both traditional geologic mapping techniques as well as new mapping technologies. The Glaciated Regions Project utilizes geophysical methods to characterize the subsurface, geochronologic analyses to determine how and when the sediments were deposited, and laboratory analyses to identify sediment properties and mineral content. The Great Lakes region is home to 26 percent of the Nation's population, yet covers only 15 percent of its area (U.S. Census Bureau, Population Division, 2022). The region produces 21 percent of the Nation's natural sand and gravel (U.S. Geological Survey, 2025), a resource extracted from glacial deposits, resulting in a lower cost per ton compared to material derived from States outside the region. Currently, quantified sand and gravel aggregate resources do not include materials within extensive aquifers and recharge areas that supply major population centers such as New York City and Chicago. The Great Lakes region also contains 35 percent of the Nation's Superfund sites (U.S. Environmental Protection Agency, 2024) because of its history as an early industrial powerhouse due to its geologic resources, underscoring the need for geologic characterization and quantification. 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T. 134 N. ¤ ) ) ) ) ) ) ) ) ) ¤ ) ) ) ) ) ) ) ) Backus Bena Boy River Cass Lake Chickamaw Beach East Gull Lake Federal Dam Hackensack Lake Shore Longville Pillager Pine River Remer Walker Creek Stony Brook Behler Creek Pine River Hay Creek Beaver Little Swan Creek Pillager Creek Mosquito Hoblin Creek Sevenmile Pine River, Home Brook Brittain Iron Cat McCackron East Mosquito Farnham Bungo Creek Mayo Brook Big Swamp Poplar Creek Dabill Creek Tower Creek Brook Pine River Willow River River Wing Crow Brook Daggett Swan Creek Mississippi River Wing Crow River Creek Creek Creek Creek Creek Creek Creek South Fork Creek Dog Lake Rock Lake Steamboat Lake Roosevelt Lake Gull Lake Norway Lake Leech Lake Portage Lake Lake Webb Lake Larson Lake Birch Lake Boss Lake Pleasant Big Portage Lake Pine Mountain Lake Lindsey Lake Woman Lake Inguadona Lake Girl Lake Man Lake Baby Lake Kid Little Boy Lake Hunter Lake Widow Lake Black Water Lake Sand Lake Hand Lake Lake Ada Town Line Lake Lake Silver Lake Boy Lake Little Sand Lake Big Sand Lake Mabel Lake Twin Lakes Trelipe Bass Lake Island Lake Cass Lake Little Wolf Lake Moss Lake Lower Sucker Lake Lake Thirteen Portage Lake Crooked Lake Swamp Lake Portage Lake Drumbeater Lake Skunk Lake Sugar Lake Kabekona Lake Winnibigoshish Rice Lake Child Lake Sylvan Lake Cat Lake Bass Lake Duffney Lake Long Lake Green Bass Lake Pillager Lake Harlan Lake Hardy Lake Ruth Lynch Lake Mile Lake Mud Lake Goose Lake Spot Lake Spider Lake Little Sand Lake Minnow Lake Scribner Lake Pig Lake Clear Lake Cow Lake Boot Lake Tamarack Lake Sand Lake Green Lake Rat Lake Moose Lake Upper Loon Lake Lova Lake Kelly Lake Omen Lake Goose Lake Deer Lake Hardy Lake Gould Lake Wabegon Lake Lake Long Jack Lake Lake Alice Gadbolt Lake Hove Lake LostLake Blue Bill Lake Scoffner Lake Little Bass Lake Horseshoe Lake Crystal Lake Trillium Lake Chub Lake Long Lake Little Boy Lake Hiram Lake Pickerel Lake North Haynes Lake South Haynes Lake Crooked Lake Island Lake Horseshoe Lake Long Lake Rainy Lake Brockway Lake Goose Lake Tamarack Lake Jack Lake McCarthey Lake Camp Lake Island Lake Long Lake Number Two Eagle Lake Round Lake Louis Lake Peterson Lake Blind Lake Bass Lake Harriet Lake Blackduck Lake Iverson Lake Camp Lake Horseshoe Lake Three Island Lake Cedar Lake Lundeen Lake Maple Lake Dirty Nose Lake Long Lake Lucille Lake Lower Milton Lake Knights Lake Wilson Lake Portage Lake Moon Lake Oxbow Lake Wax Lake Mud Lake Little Bass Lake Michaud Lake Kidney Lake Coffin Lake Deer Lake White Oak Lake Mitten Lake Stevens Lake Lake Twentysix Oxbow Lake Andrus Lake Leavitt Lake Lawrence Lake Pistol Lake Upper Gull Lake Horseshoe Lake Swede Lake Lizotte Lake Smoky Hollow Lake Drewery Lake Lydick Lake Twin Lake LittleTwin Lake Little Moss Lake Life Raft Lake Tamarack Lake Ten Lake Little Portage Lake Rice Lake Nushka Lake Hole-in-Bog Lake Chub Lake Little Vermillion Lake Sailor Lake Windy Lake Cedar Lake Ahsebun Lake Kelly Lake Reservoir Lake Egg Lake Shafer Lake May Lake Mud Upper Lake Loon Lake Lake Little Webb Lake Stony Lake Tenmile Lake Broadwater Bay Wilson Bay Sucker Bay Steamboat Bay Traders Bay Agency Bay Walker Bay Headquarters Bay Boy Bay Pike Bay Sixmile Lake Mud Lake Goose Lake Swift Lake Lake Lomish Lower Trelipe Lake Laura Lake Thunder Lake Big Rice Lake Washburn Lake Lake George Hay Lake Ponto Lake Lake Hattie Lake Lake Pine Long Lake Welsh Lake Grass Lake Middle Sucker Lake Vermillion Lake Rat Lake Birch Lake Variety Lake Jackpine Lake Big Deep Lake Mule Lake Wabedo Lake Little Thunder Lake Bowen Lake Ox Yoke Lake Four Point Lake Morrison Lake Bay Big Bass Lake Grave Lake HUBBARD COUNTY 0-50 51-100 101-150 151-200 201-250 251-300 301-350 351-400 401-450 501-550 551-600 601-650 651-700 701-750 751-800 801-850 Figure 3.  Depth to bedrock map produced as part of the Minnesota Geologic Atlas of Cass County, Minnesota (Lusardi and others, 2018). Figure 4.  Photograph showing a U.S. Geological Survey (USGS) scientist analyzing an outcrop of sand and gravel in Fort Drum, New York. Photograph by G. Colip, USGS.

ISSN 2327-6916 (print) ISSN 2327-6932 (online) ://doi.org/10.3133/fs20263010 References Cited Lusardi, B.A., Pettus, M.C., Chandler, V.W., Radakovich, A.L., Nguyen, M.K., Staley, A.E., Hamilton, J.D., 2018, C-43, Geologic Atlas of Cass County, Minnesota: Minnesota Geological Survey County Atlas Series C-43, 6 pls., scale 1:200,000, accessed July 26, 2025, at ://conservancy.umn.edu/items/a64a453b-61a3-4b60-822df2a074639eef. Rawling, J.E., III, Carson, E.C., Attig, J.W., Mickelson, D.M., Mode, W.N., Johnson, M.D., and Severson, K.M., 2025, Quaternary geology of Wisconsin: Wisconsin Geological and Natural History Survey map 512, scale 1:500,000, accessed April 30, 2026, at ://doi.org/10.54915/ 9883. Rupp, R.F., Tripp, D.C., Loope, H.M., Antinao, J.L., Johnson, M.R., Nash, T.A., and Norris, T.A., 2021, Bedrock elevation of the Berne, Domestic, Geneva, and Willshire 7.5‑minute quadrangles, Indiana-Ohio: Indiana Geological and Water Survey, Indiana Journal of Earth Sciences, v. 3, scale 1:48,000, at ://doi.org/10.14434/ijes.v3i1.31742. Swezey, C.S., Blome, C.D., Kincare, K.A., Lundstrom, S.C., Stone, B.D., Sweetkind, D.S., Berg, R.C., Brown, S.E., and Yellich, J.A., 2022, Implementation plan of the National Cooperative Geologic Mapping Program strategy—Great Lakes (Central Lowland and Superior Upland Physiographic Provinces): U.S. Geological Survey Open-File Report 2021-1120, 24 p., accessed July 2025 at ://doi.org/10.3133/ ofr20211120. U.S. Census Bureau, Population Division, 2022, Annual estimates of the resident population for the United States, Regions, States, District of Columbia, and Puerto Rico—April 1, 2020, to July 1, 2022, NSTEST2022-POP: U.S. Census Bureau database, accessed December 16, 2022, at ://www2.census.gov/programs-surveys/popes/ tables/2020-2022/state/totals/NST-EST2022-POP.. U.S. Environmental Protection Agency, 2024, Search for Superfund sites where you live: U.S. Environmental Protection Agency website, accessed December 10, 2024, at ://www.epa.gov/superfund/searchsuperfund-sites-where-you-live. U.S. Geological Survey, 2025, USGS aggregates time series data by State, type, and end use: U.S. Geological Survey dataset, accessed April 24, 2025, at ://www.usgs.gov/media/files/usgs-aggregates-time-seriesdata-state-type-and-end-use. By Brianna Lopez, Jenna L. Shelton, Michael Marketti, Kate Ritzel, and Brandon L. Graham For more information, please contact: GLGMC Program Officer GLGMC@usgs.gov ://www.usgs.gov/programs/national-cooperative-geologic-mappingprogram U.S. Geological Survey National Cooperative Geologic Mapping Program 12201 Sunrise Valley Drive, Mail Stop 913 Reston, Virginia 20192 Publishing support provided by the U.S. Geological Survey, Science Publishing Network, Baltimore and Reston Publishing Service Centers Edited by Bree McCloskey Illustration support and layout by David Bruce

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