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Home , Animikie Group, Michipicoten Island, Oronto Group, Penokean orogeny, Rove Formation, Sioux Quartzite

Copper Harbor Gunflint Formation: Breccia with white Geologic Events in the Mid-Continent of North America G-012011-1E 1 inch (Century Mine, Upper Peninsula MI) (Sibley Peninsula, Thunder Bay, ON) Compiled by: Steven D.J. Baumann, Alexandra B. Cory, Micaela M. Krol, Elisa J. Piispa Updated March 2013

Oldest known rock showing a dipole magnetic field: red dacite in Austrailia

Paleomagnetic Line

3,800 3,700 3,600 3,500 3,400 3,300 3,200 3,100 3,000 2,900 2,800 2,700 2,600 2,500 2,400 2,300 2,200 2,100 2,000 1,900 1,800 1,700 1,600 1,500 1,400 1,300 1,200 1,100 1,000 900 800 700 600 500 Paleozoic Period Stenian Eon

Pass Lake Kama Hill Sibley Group (Sibley Basin, Thunder Bay Area, ON) McGrath Gneiss McGrath Complex (EC MN) Metamorphic and cataclastic event Formation Formation Outan Island Formation Formation Island Outan Formation Nipigon

Recent Era of Great Mid-continent Basin Formation (MI, IL, IA, IN, KY, MO) 2 inches

Marshfield Archean Gneiss (C WI) Linwood Archean Migmatite (C WI) Sudbury Swarm (SE ON)

Quinnesec Formation Intrusions (NE WI) Quinnesec Formation (NE WI) Hatfield Gneiss (WC WI) Pre-Quinnesec Formations deposited (NE WI) Upper Baraboo LEGEND (Sibley Peninsula, Thunder Bay, ON) Gray granodioritic phase Montevideo Gneiss (SW MN) Red phase Montevideo Gneiss (SW MN) High-grade metamorphism Basal Sioux Rhyolites (SW MN, SE-SC SD, NW IA, NE NB) (North Limb, Rock Springs, WI) North Shore Volcanics (EC NE MN, S ON) = Shallow Igneous Marquette & Marcellon Rhyolite Tuffs (SC WI) ? Waterloo and related (EC WI) Mellen Intrusions (N WI) Mineral Lake Intrusions (N WI) = Deep Igneous Cedar Rapids & Washington County Quartzites (SE IA) 0.5 inches Biotite gneiss and amphibolite Migmatic granite and pegmatite Morton-Sacred Heart Granitic Terrain (SW MN) Sacred Heart Granite copper and zinc mineralization (N WI) ? Morton-Sacred Heart Granitic Terrain (SW MN) = or Caldera Powder Mill Group Volcanics (N WI, UP MI) Bergland Group Volcanics (N WI, UP MI) Montello Granite Intrusion (NC WI) Stettin & Wausau Syenite Complexes (C WI) = Hydrothermal Event deposition of copper deposits (UP MI) Camery Lake Gneiss Baxter Hollow Granite Intrusion (SC WI) Ninemile Granite (C WI) Seely Dake Quartzite Freedom Formation Slate Creek Rowley Marathon Lamprophyres (S ON) = Ash Flows Algoma Series (ON) Baraboo sands deposited Post Baraboo formations deposited (SC WI) Southern -Michisota Crustal Collapse Caldwell Complex (S ON) Crystal Lake (S ON) = Sedimentary Wolf River Intrusion (C WI) Keewatin Series Volcanics (Sudbury, ON area) McGrath Gneiss & Ortonville Granite (EC MN) Southern - Crustal Collapse Baraga-Marquette (Little Mountain Dikes) (UP MI) = Sedimentary Wolf River Hydrothermal Event (SC-C WI) Michipicoten (Wawa ON)

= Banded Formation (Sedimentary) Lyon County Gneiss Baraboo Rhyolites (SC WI) Ely’s Peak (2,532mya) (NW IA) Metamorphism of Baraboo, Souix, & Waterloo Quartzites (SC EC WI) Otter Creek Mafic Complex Matlock (NW IA) (2,890mya) (NW IA) ? Marathon-Abitibi Lamprophyre Dikes (S ON) 2 inches Jacobsville = Baraboo Sedimentary Baraboo/Sioux Interval (Wisconsin, Minnesota, ) (Root River, Sault Ste. Marie, ON) Portage Lake Volcanics (UP MI & NW WI)

= Sedimentary Rocks with some glacial Watersmeet amphibolite-gneiss leucogranite intrusions deposition of copper, gold, and uranium deposits (S ON) diamictites Watersmeet amphibolite-gneiss Powder Mill Group (UP MI) 4 inches Watersmeet initial metamorphic event ? (second metamorphic event) Watersmeet third metamorphic event = Baraboo and Related Metamorphism deposition of sedimentary rocks within the Watersmeet volcanics ? Watersmeet fifth metamorphic event Watersmeet tonalite (emplacement) Watersmeet gneiss (W UP) Watersmeet gneiss (W UP) Thayer Granite Watersmeet fourth metamorphic event Eastern Granite/Rhyolite Southern Granite/ = Metamorphism (all colors) metamorphism of Marshfield copper deposition of sedimentary rocks within the Marshfield Exotic Terrane ? Rhyolite Interval Marshfield Exotic Terrane (NW IA) ? Exotic Terrane Interval (NE NB -NW IL) mineralization in the (SE NB) Nonesuch

= Unsure Time-span (all colors) East Bull Lake Magma Suite (ON) Initial Huronian Compression Event Central Arch Granite (SC IA) Green Island Plutonic Group Quimby Granite (1,433mya) (NW IA) (1,485mya) (E IA, NW IL) Hull Keatophre Jacobsville Formation (ON, UP MI) (1,782mya) (NW IA) Spencer Granite (NW IA) Bear Lake Rhyolite Stock (1,062mya) = Basin Formation Clastic and chemical Sediments in Beardmore-Geraldton Belt (Lake Nipigon ON) Cobalt Formation Nonesuch Camp Quest Gneiss Harris Granite Nippissing metamorphism of (1,804mya) (NW IA) Orienta Formation Devils Island Formation Group (2,065mya) (NW IA) Freda Chequamegon Formation Intrusions Camp Quest Gneiss Oronto Group (N WI, UP MI) ConglomerateCopper Harbor (N WI, UP MI) = Regional Compression Jubilee Stock (Wawa ON) Huronian Formation Volcanics Central Plains Interval (Iowa, , Missouri) Lakeshore Traps (1,087.2mya) Michipicoten Island Intrusion (1,086mya) Matachewan (Algoma, ON) Elliot Lake Hough Lake Lorrain Huronian Hydrothermal Event Group Group Group Lake Quirke Formation Gowganda Formation Gordon LakeFormation Formation River Bar Athelstane (Amberg) Pink Granite (NE WI) Nopeming Sandstone (NE MN) = Ore deposition Amberg Gray Granite (NE WI) Huronian Supergroup second metamorphic of the Marquette Range Supergroup Bessemer Quartzite (UP MI & NW WI) Lower Red Clastics (C IA) Upper Red Clastics (C IA) = Mountain Building Event Huronian Interval (Southern Ontario) initial metamorphism of the Marquette Range Supergroup third metamorphic of the Marquette Range Supergroup Fond du Lac Formation Formation Fond du Lac Solor Church Group (E-SE MN) Hinckley Sandstone Bayfield Group (NE-E-SE MN, NW WI) Dickerson Group Placer deposits of Uranium in diamictites Hiawatha Graywacke = Meteor Impact Stambaugh Formation Paint River Group = Glacial Event Six-Mile Lake Lake Six-Mile Amphibolite Solberg Schist East Branch Arkose Iron River/Crystal Falls District Greenstone Badwater Fortune Lakes Slate Dunn Creek Slate Formation Iron Riverton

Deposition of the Mona Schist, Light House Point Member Vulcan Iron Formation = Known unknown event resetting of dates in felsic intrusions or true dates ? 3 inches Deposition of the Mona Schist, Undivided Fern Creek Formation Sturgeon Randville Dolostone Menominee Range Felch Michigamme Slate Gowganda Argillite, Quartzite Formation = Accretion of Supercontinents Metamorphism of the entire Mona Schist Interval (MN, WI, UP MI, ON) Huronian Supergroup Kona sulfide and copper depositional mineralization (Route 638, Leeburn, ON) = Break-up of Supercontinents Bell Creek Gneiss Compeau Creek Gneiss Baraga Group Middle Run Formation (E IN, NC KY, W OH) 1 inch Syenite Intrusion in the Huronian Supergroup

Group Route 17, Dresbrats, ON)

Bell-Compeau Creek Complex Menominee Ajibik Formation Formation Siamo Enchantment Lake Wewe Formation Marquette VolcanicsHemlock Iron Bijiki Formation Michigammee = Large Continents within or independent Menominee Range and Formation Mesnard Quartzite Quartzite Goodrich Black Michigammee MemberIron Slate and Formation Kona/Saunders Formation of Supercontinents Negaunee Iron Formation ) unnamed basalts

primary Copps Michigammee SE MO Ramsay Formation Sunday Quartzite Bad River Dolostone Eastern Gogebic Iron Range Formation Formation = Regional BIF depositional events metamorphic event Formation Ironwood Iron Endion

Western Gogebic Iron Range Palms Tyler = Continent wide metamorphic regime Formation Formation

Emperor Volcanics ? ) = Era of major emplacement Chocolay Group Cloud River NW Dike dated unnamed basement basalts (W OH) Kekabeka Gunflint Rove MO SE Gunflint Range Quartzite Gunflint Carbonate-Iron Formation Formation (1,325mya) (1,284mya) Victoria River NW Dike = Sudbury impact layer present Puritan Quartz Monzonite Monzonite Quartz Puritan Pokegama Virginia and Emily District Unnamed Quartzite on top of the Quartzite Biwabik Iron Formation Formation Logan Sills Reany Creek Formation Precambrian Stramatolitic Carbonates ( Carbonates Precambrian Stramatolitic Tuffaceous BIF ( Hardwood Gneiss (S UP MI) Marquette Range Supergroup Carbonate Carbonate Iron-Chert Unnamed

= Questionable event Member Black Slate Michigammee ? Michigammee Middlebrook Group & Older Ash Flows &Tuffs (SE MO) Ketcherside Tuff (SE MO) Nipigon Sills Reany Creek Formation Baraga & Dead River Basins Formation Firmly Dated NE Dike ) Pigeon River Dikes Lorraine Quartzite, ? = Known only from seismic profiling, Hawn Park Foliated Granodiorite (SE MO) exact chronological position is unknown Mille Lacs Group SE MO Huronian Supergroup Baraga Group 3 inches Osler Group Volcanics ) Sananaga Tonalite Sananaga Batholith (Route 17, Echo Bay, ON) Silvermine Granite (SE MO)

unnamed (1,870mya) Emily Member Icarus Pluton North Range Group Logan Igneous Suite (Thunder Bay area, ON) Formation Formation Lake Rabbit Royal Gorge Rhyolite( Gorge Royal Denham Formation Trout Lake Formation Mahnomen Mahnomen Formation Snowbank Lake Pluton Lac La Croix Granite Formation Township Glen Thomson Formation Little Falls Formation Western St. Francois Mtn. Volcanics (SE MO) NE MN, W ON MN, NE ( Lorraine Puddingstone, Huronian Supergroup Trommald Formation Giants Range Batholith Huronian Interval (Minnesota & ) 1 inch (Route 638, North of Bruce Mines, ON) Animikie Interval (South Central Michigan to Thunder Bay Ontario) Breadtray and Butler Hill Granite (SE MO) 1 inch

Newton Belt Newton Lake Formation Bradbury Creek Granodiorite (EC MN) Cutler Granite Intrusion (ON) Munger Granite Porphyry (SE MO) = Reversed Polarity

= Normal Polarity Bass Lake Sequence Vermilion District = Transitional/ Rapid Reversal Polarity Upper Ely Greenstone Knife Lake Group St. Francois Batholith Hyrdothermal Event(s) ? (SE MO) = Period of Non Dipole Magnetism dated Illinois basement granites (N-C IL) = Unknown Polarity Soudan Iron Formation Lake Vermilion Formation Northeastern Wisconsin Pre-Dunbar Gneiss Basement ? ? Enterprise Sequence (C-E IL) Lower Ely Greenstone

N = North Soudan Belt South Sub-Centralia Sequence (S-C-E IL) ? North Sub-Centralia Sequence (S-C-E IL) ? Centralia Sequence (N-C IL, W IN, WOH) S = South Britt Sequence Gafvert Lake Sequence W = West Ozarkian Interval (South East Missouri to North-Central Illinois) E = East 3 known metamorphic events Gunflint Formation: seam agate C = Central (Thunder Bay, ON) IA = Iowa

IL = Illinois Reel Foot Rift Rough CreekGraben

KY = Kentucky Great Lakes Tectonic Compression I Great Lakes Tectonic Rupture I Great Lakes Tectonic Compression II Great Midwest Caldera and Hydrothermal Events Lake Superior and Mid-Continent Rifting Mid-Continent Rift Compression New Madrid Seismic Zone MI = Michigan Negaunee Formation: banded iron formation MN = Minnesota Great Lakes Tectonic Rupture II (Ishpeming area, Upper Peninsula MI) MO = Missouri No known sedimentary rocks in the Midwest Erosion dominant Erosion dominant Erosion dominant throughout Erosion dominant throughout the Midwest NB = Nebraska throughout the throughout the the Midwest OH = Ohio Midwest Midwest ON = Ontario Late Heavy Bombardment Period Yavapai SD = South Dakota 0.5 inches UP = Upper Peninsula Amethyst in Archean Monzonite (NE of Thunder Bay, ON) WI = Wisconsin ? Trans-Hudson Orogeny Mazatzal Orogeny Unnamed Orogeny in Southern Ontario Wopmay Orogeny Grenville Orogeny Algoman/Kenoran Orogeny Impact Event ? Levels reach 21% Oxygen Levels reach 1% Oxygen Levels reach 5% Free Oxygen begins to accumulate in the atmosphere

Vermilion-Dickerson Pre-Sudbury BIF Subevent Post Sudbury BIF Baraboo BIF Event Ozark BIF Event (Unnamed) Subevent BIF Event G1 G2 G4 Superior BIF Event ? Kiagas Kiagas Sturtian Marinoan Gaskiers G3, A, B, &C ? Sudbury Impact Event (Unnamed) (Unnamed) Huronian

1 foot

Pannotia Vaalbara Ur Kenorland Columbia (Nuna) (Vendia) Protocontinent Protocontinent Supercontinent Supercontinent Supercontinent 0.5 inches Archean Greenstones Arctica Laurentia Laurentia Laurentia (Route 17, Wawa area, ON) (Pre-Laurentia)

Pre-modern Transition to Modern Plate Tectonics Modern Plate Tectonics Modern Plate Tectonics Hiatus ? Modern Plate Tectonics

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Reflection Data, USGS Professional Paper 1538-Q GSC = Geological Survey of Allen, R.C., 1915, Contributions to Precambrian Geology of Northern Michigan and Wisconsin, Michigan Geological and Biological Survey, Publication 18, Geological Series 15 Fritts, C.E., 1969, Bedrock Geologic Map of the Marenisco-Watersmeet Area, Gogebic and Ontonagon Counties, Michigan, USGS Map I-576 LaBerge, G.L., 1983, Precambrian Geology of Marathon County, Wisconsin, Wisconsin Geological and Natural History Survey, Information Circular 45 o o ILSG = Institute on Lake Superior Geology Pratt, W.B., 1979, Geologic Map of Exposed Precambrian Rocks, Rolla 1 X2 Quadrangle, USGS Miscellaneous Investigation Series Map I-1161 Annells, R.N., 1975, Geology of Michipicoten Island Ontario, GSC Bulletin 218, Map 1353A Gair, J.E., 1968, Geology of the Marquette and Sands Quadrangles Marquette County Michigan, USGS, Professional Paper 397 LaBerge G.L., 1991, New Observations of the Age and Structure of Proterozoic Quartzites in Wisconsin, USGS Bulletin 1904-B ISGS = Illinois State Geological Survey

Puffett, W.P., 1969, The Reany Creek Formation, Marquette County Michigan, USGS Bulletin 1274-F KYGS = Kentucky Geological Survey Baumann, S.D.J., 2010, Lithostratigraphy and age of the Jacobsville Formation around the Lake Superior Basin, U.S.A. and Canada, MIGE G-122010-1A Green, J.C., 1982, Geologic Map of Minnesota, Two Harbors Sheet, Scale 1:250,000, State of Minnesota, University of Minnesota Lowell, G.R., 1975, A Field Guide to the Geology of the St. Francois Mountains, Missouri, Big Rivers Area Geological Society MIGE = Midwest Institute of Geosciences and Engineering

Robertson, J.A., 1977, Geology of the Cutler Area District of Algoma, Ontario Division of Mines, Geoscience Report 147 MNGS = Minnesota Geological Survey Baumann, S.D.J., 2011, Preliminary Redefinition of the Cobalt Group (Huronian Supergroup), in the Southern Geologic Province, Ontario, Canada, MIGE G-012011-2A Hansen, M.C., 1997, The Geology of Ohio-The Precambrian, OHGS Geofacts #13 Miller, J.D., 2009, ILSG Ely, Minnesota, Proceedings Volume 55, ILSG Trip Guidebook Vol. 55 Part 2 OHGS = Ohio Geological Survey Rust, B.R., 1987, The Sedimentology and Depositional Environments of the Huronian Bar River Formation, Ontario, ONGS Open File Report 189 Bennett, G., 1982, Geology of the Two Horse Lake Area, ONGS Report 210 Hart, T.R., 2006, Keweenaw Rocks of the Mamainse Point Area, ILSG Field Guide 52 Vol. 52 Part V Miller, J.D., 2010, Field Guide to the Geology of the Precambrian Iron Formations in the Western Lake Superior Region, Minnesota and Michigan, PRC Professional Workshop Series October 10 to ONGS = Ontario Geological Survey

October 16, 2010, University of Michigan Ryder, R.T., 1997, Stratigraphic Framework of and Rocks in the Appalachian Basin from Campbell County, Kentucky, to Tazewell County Virginia, USGS I-2530 PRC = Precambrian Research Center Bennett, G., 2006, The Huronian Supergroup Between Sault Ste. Marie and Elliot Lake, Ontario, ILSG, Vol. 52, Part IV Hinke, J., 2007, Detailed Surficial Geologic Mapping and Terrain Analysis of the Blue Hills Felsenmeer Valley, Rusk County, Wisconsin, Department of Geology University of Wisconsin Eau Claire USGS = Geological Survey Morey, G.B., 1988, Correlation of the Precambrian Rocks of the Lake Superior Region, United States, USGS, Professional Paper 1241-F Schmidt, R.G., 1976, Geology of the Precambrian W (Lower Precambrian) Rocks in Western Gogebic County, Michigan, USGS Bulletin 1407 Bornhorst, J.J., 1994, Self Guided Geological Field Trip to the Keweenaw Peninsula, Michigan, ILSG, Vol. 40, Part II Hollings, P. (Editor), 2012, Thunder Bay Ontario, Field Trip Guidebook, ILSG, Vol. 58, Part II

Morey, G.B., 1967, and Petrology of the Type Fond du Lac Formation, Duluth Minnesota, MNGS Report of Investigation 7 Siemiatkowska, K.M., 1977, Geology of the Wakomata Lake Area District of Algoma, Ontario Division of Mines, Geoscience Report 151 Boyun, B.H., 1964, The Marquette Mineral District Michigan, The Cleveland-Cliffs Iron Co. Holst, T.B., 1991, The Penokean Orogeny in Minnesota and Upper Michigan-A Comparison of Structural Geology, USGS Bulletin 1904-D

Morey, G.B., 1969, The Geology of the Precambrian Rove Formation in Northeastern Minnesota, MNGS Special Publication Series, SP-7 Sims, P.K., 1985, Geology and of Granitoid and Metamorphic Rocks of Late Archean Age in Northwestern Wisconsin, USGS Professional Paper 1292-C Braile, L.W., 1986, Tectonic Development of the New Madrid Rift Complex, Mississippi Embayment, North America, Tectonophysics, 131(1986)1-21 Holst, T.B., 1991, Tectonic Imbrication and Foredeep Development in the Penokean Orogen, East-Central Minnesota-An Interpretation Based on Regional Geophysics and Results of Test Drilling, USGS Bulletin 1904-C Morey, G.B., 1977, Revised Keweenawan Subsurface Stratigraphy, Southeastern Minnesota, MNGS Report of Investigation 16 Sims, P.K., 1984, Geology, Geochemistry, and Age of Archean and Early Proterozoic Rocks in the Marenisco-Watersmeet Area, Northern Michigan, USGS Professional Paper 1292-A Brown, V.M., 1988, Geologic Map of Precambrian Rocks Des Arc NE Quadrangle, Iron and Madison Counties, Southeast Missouri, USGS Miscellaneous Field Studies Map MF-2032 Jackson, S.L., 1994, Geology of the Aberdeen Area, ONGS Open File Report 5903 Morey, G.B., 1978, Lower and Middle Precambrian Stratigraphic Nomenclature for East-Central Minnesota, MNGS Report of Investigation 21 Sims, P.K., 1985, Great Lakes Tectonic Zone-Revisited, USGS Bulletin 1904-S Cannon, W.F., 1980, Copper Bearing Quartzite Near Watersmeet Michigan, USGS Open File Report 80-390 Jackson, S.L., 2001, On the Structural Geology of the Southern Province between Sault Ste. 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Marie and the Blind River Area, ONGS, Map 2670 Nachatilo, S.A., 1993, Structural Analysis of the Archean Rocks in the Negaunee Area, Michigan—Constraints on Archean verses Early Proterozoic Deformation, USGS, Bulletin 1904-O Taylor, G.L., 1972, Stratigraphy, Sedimentology and Sulfide Mineralization of the Kona Dolomite, Michigan Technological University Craddock, J., 2006, Precambrian Evolution of Minnesota, 19th Annual Keck Symposium, 120-125 Kisvarsanyi, E.B., 1976, Geology of Missouri with Guidebook to Parts of the St. Francois Mountains, 23rd Annual Meeting of the Association of Missouri Geologists, Report of Investigations 61 Ojakangas, R.W., 1994, Sedimentology and Provenance of the Early Proterozoic Michigamme Formation and Goodrich Quartzite, Northern Michigan-Regional Stratigraphic Implications and Suggested Young, G.M, 2001, Paleozoic Huronian Basin: Product of a Wilson Cycle Punctuated by Glaciations and a Meteorite Impact, Sedimentary Geology 141-142 (2001) 233-254 Dott, R.H., 1970, Geology of the Baraboo District Wisconsin, Geological and Natural History Survey, Information Circular 14 Correlations, USGS Bulletin 1904-R Klasner, J.S., 1991, Nature and Style of Deformation in the Foreland of the Early Proterozoic Penokean Orogen, Northern Michigan, USGS Bulletin 1904-K Van Schmus, W.R., 1998, Proterozoic Granite Systems of the Penokean Terrain in Wisconsin, International Field Conference, Wisconsin Geological and Natural History Survey, Drahovzal, J.A., 1992, The East Continent Rift Basin: A New Discovery, KYGS Information Circular 57 Ojakangas, D., 2009, Geology and Metamorphism of the Eastern Mesabi Range, ILSG Field Trip Part II, Field Trip 5 Open File Report 1998-10 Kolata, D.R. (Editor), 2010, Geology of Illinois, ISGS University of Urbana Champaign, 1st Edition, ISBN: 978-0-615-41739-4 Dressler, B.O., 1995, New Observations at the Slate Islands Impact Structure, Lake Superior, ONGS Miscellaneous Paper 164 53-61 (1995) Nachatilo, S.A., 1992, Structural Analysis of Archean Rocks in the Negaunee Area, Michigan-Constraints on Arhean verses Proterozoic Deformation, USGS Bulletin 1904-O various authors, 1973, Guidebook to the Precambrian Geology of Northeastern and Northcentral Wisconsin, ISGS Vol. 19, Wisconsin Geological and Natural History Survey LaBerge, G.L., 1994, Geology of the Lake Superior Region, Geosciences Press, Inc., ISBN: 0-945005-15-6 Dutton, C.E., 1981, Geology of the Florence Area, USGS Professional Paper 633 Paull, R.K., 1978, Precambrian Inliers in South-Central Wisconsin, Wisconsin Geologic and Natural History Survey various authors, 2001, Field Trip Guidebook Madison Wisconsin, ILSG Proceedings, Vol. 47 Part II

Piispa, E.J., 2010, Paleomagnetism of the Mid-Continental Rift System, Rocks from the Thunder Bay Area (Ontario Canada): New Data and Questions, Poster Presentation, Michigan Technological White, W.S., 1972, The Base of the Upper Keweenawan, Michigan and Wisconsin, USGS Bulletin 1354-F University Wood, J., 1975, Geology of the Rawhide Lake Area District of Algoma, Ontario Division of Mines, Geoscience Report 129