Prepared with Support from the REGIONAL HYDROGEOLOGIC ASSESSMENT RHAÐ4, PART A MINNESOTA GEOLOGICAL SURVEY MINNESOTA DEPARTMENT OF NATURAL RESOURCES, DIVISION OF WATERS Plate 1—Surficial Geology D.L. Southwick, Director

R. 48 W. R. 47 W. ° 95°15' 96 30' R. 46 W. Qoh R. 45 W. 96°15' R. 44 W. R. 43 W. 96°00' R. 42 W. R. 41 W. 95°45' R. 40 W. R. 39 W. 95°30' R. 38 W. R. 37 W. Qoh Qtfr Qtbr Qoh Qtfd Qthd Qtfr Qgl Qthd Camp ek Dry re Wood Qtfr Lake Lake C Qsw Thielke Qtfr Qdb Qlb Qtfr Qdb Hassel Lake Qtbr Lake Qoh Lake Qsh Clontarf Moore Qthd Qtbr C Qdb Qlb Qssd Bentsen h Lake Qdb ip 29 Lake Qoh Qdb p Johnson Qtld ewa B A ig Qtbr Qlb Qtfr rtichoke Qtld Qoh T. 122 N. T. 122 N. Stone Qsh Qdb Long 75 9 Qdb 9 Lake Qtbr Qoh Qdb Mud Qtbr Lynch Qlb Qoh Large Lake Qsh River River 7 Henry Lake

Larson Qlb East Qlb SURFICIAL GEOLOGY Lake Lake Lake Oliver ChippewaQsh Lake ranch Qoh Qoh Qsh B Qtfd 59 Qdb 9 Monson Lake Qtfr Qoh Qlb Qoh Qtfd By Qoh Benson Lake Long Qtfr Griffin W. Sunburg Tom Qtfr Lake Frank Lake Lake Qoh Qthd Ortonville Qtbr Hollerberg Carrie J. Patterson, Alan R. Knaeble, Sara E. Gran, and Stephanie J. Phippen 12 Lake River Qtfd Qtld Qtbr Qtld Qsh Qtld Qtbr Qtld Terre 12 1999 Qdb T. 121 N. Qlb Qtfr Qtbr Qdb T. 121 N. Qtfr Hart de Danvers PA Lake Qlb 12 Qsw Qtfr Qdb Qtld Big Stone Qlb Odessa PA Qtld Qoh Qdb Qdb De Graff Qlb Qdb Qgl Qsw Qtld Qtfd ° Qsw Qtfd Shible 45°15' 45 15' Lake Qdb Qlb Qtfd PA Pomme Qtfd 7 Holloway Swift Qgl Qoh PA Qtfd Qsw Qdb Qoh Qdb Qsw Qtfd Qsh Qtld Murdock Qdb 12 Qoh Qlb Qsw Appleton Qsd Qsh Qtld PA CORRELATION OF MAP UNITS Qsd 75 Qlh Ice Deposits T. 120 N. Qtfd r (Locally modified by later surficial processes) e Qsh Stream Deposits Lake Deposits Bedrock v Kerkhoven T. 120 N. i Qlb Qsw R Qsw Marsh Lake Qtfd C Qtfd o Qdb t Qtsd t o

n Qoh w C Qtld o hipp Qsw Qsh Qlh Qoh Holocene Qtfd o ewa d Qtld Qlh 29 Qdb C

QUATERNARY reek Qoh Late Lac qui Parle Lake Qtfd Qtfd Qtfr Qtbr Qssd Qsd Qsld Qdb Qgl Qlb Shakopee Wisconsin Pleistocene Qlh Qlb Lake Qthd Qtmd Qtad Qtfd Qtld Qtsd Bellingham Qsw 7 major Qdb Qlh Qsh Qdb unconformity Qtfd PROTEROZOIC 59 PA Qlb Qoh AND ARCHEAN Qsw Qlb 119 Qoh Milan 40 Qlb 40 T. 119 N. Qsd Qoh T. 119 N. Qtfd Qsw Qdb Qtld Qsw

Qssd Qtfd Qoh Qssd NassauQsh Qoh 75 Qsw Qoh Qoh Qtld Qlb Qlh Qtsd L Qsw Qtsd ac qu Qlh i 29 Qoh Pa DESCRIPTION OF MAP SYMBOLS Qoh rle Lake Qdb DESCRIPTION OF MAP UNITS for Marshall phase, 20Ð30 percent, for Antelope phase, 30Ð50 percent), and some Qsw Qtfd Qtfd Weather lignite. Till surface has low relief. Locally overlain by thin (about 10Ð20-feet Geologic contact—Approximately located; established from aerial photographs, Dry C Chippewa HOLOCENE AND LATE PLEISTOCENE r e Qoh e Qlb Qoh Organic deposits—Peat and sediment deposited in marshes and shallow lakes. thick), discontinuous, supraglacial and englacial sorted sediment and till that geomorphology, and examination of surficial material and soil maps. k T. 118 N. Typically found in depressions interpreted to have formed through melting of typically form linear ridges. The sediment is interpreted to have been localized Scarp—Ticks point down scarp; established from aerial photographs and T. 118 N. Qoh Qtfd Qsh buried glacial ice and along former glacial stream channels. Some deposits have by crevasses in stagnant ice. topographic maps. Where paired, interpreted as former drainageway. Not Qsd Qlb 40 40 been drained. Qtld Till with lake-modified surface—Till that has at its surface a discontinuous, silty, indicated where scarp coincides with stream-related unit. In places, Marietta Madison 59Qlb Watson Ri Qlh clayey cap or a coarser, near-shore sediment. Till of all phases of the Des Moines drainageways contain organic material, lake sediment, and stream sediment; ve Qdb ° Lake sediment—Clay, silt, marl, and some organic material. The basins are commonly 45°00' r Qsh 7 45 00' lobe and the Big Stone phase of the Red River lobe, and, possibly, older glacial Qtsd Qdb shallow (less than 10 feet deep), and the sediment may be thin; some basins the deposits are commonly too small in area, too thin, or too discontinuous Qoh Qoh Qsh i Parle Qdb sediment are affected. Till texture, color, and clast lithology are similar to to map. Former drainageways may locally control the direction of present- Qtfd qu have been drained. ac Qtfd surrounding unit. The till surface has low relief. Erosion may have removed L Qlb Qsh Stream sediment—Stratified layers of silt, clay, and sand; some organic material. day surface and near-surface water flow, especially flood waters. Scarps shown Qssd The sediment is coarser in the Minnesota River channel. Commonly located fine sediment, leaving a lag of clasts at the surface. Shorelines are locally marked on the Kerkhoven washed-till plain (Fig. 2) are interpreted as having been Qdb Clara City 23 by very low escarpments, beach ridges, or deltas (sediment of map unit Qdb). Qoh Qtfd Qssd along glacial stream channels, where it may bury and incorporate coarser glacial lake cut and therefore represent former shorelines. Qsld Qlb Qtfd Till with stream-modified surface—Till modified by flowing water; fluvially eroded stream sediment. The unit is not shown in narrow channels, although it is present Deep, broad, irregular trough—Interpreted as collapsed subglacial channel Qsd Montevideo Qlb Qtsd ek and streamlined in places. Till of all phases of the Des Moines lobe and, locally, e Qtld to some extent wherever a modern stream flows. The unit includes the steep (tunnel valley) or buried valley. Some troughs now contain long narrow lakes, r Qlb 7 older glacial sediment are included in this unit. Matrix texture, color, and clast Qsd C side slopes of channels, especially along the Minnesota River, where very little such as Lake Hendricks in the extreme southwest corner of the map area. Qdb Qlb lithology are similar to the original till unit before erosion. Locally overlain 212 Qssd

stream sediment is preserved. Rather, older units are exposed in bluffs, and Dawson 7 T. 117 N. T. 117 N. ile Fan-shaped sloping hill at mouth of channel—Interpreted to be an alluvial 212 Qssd colluvial sediment covers less steep slopes. by a thin lag of sand and gravel or covered with silt and clay. Channel scars m

fan (for example, Canby fan; Fig. 2) or a delta into a lake (Boyd delta; Fig. n e

are common. Channels may localize organic deposits (map unit Qoh), lakes, Qsd T Qoh Qsw Stream sediment of Glacial River Warren—Stratified sand and gravel; commonly 2) composed of sand, gravel, and silt. Where shown on till of the Big Stone Qtfd Qssd Qsh and modern streams and flood waters. After stream modification, channels may Qtfd Qdb forms bars that protrude above Holocene stream sediment (map unit ) in the moraine (map unit Qtbr), the symbol indicates a fan-shaped lobe of till (not Qsd Qssd have collapsed from meltout of buried ice. River Warren gorge (Fig. 2). The unit is predominantly found where the river sorted sediment) that flowed into the lake basin. Lac qui Parle Qtfd Qoh PA Maynard reworked existing deposits of sand and gravel. Glacial River Warren was mostly Qtad Till of the Antelope moraine—Till that forms a low, broad ridge. Matrix texture Qtfd Qsd Qoh Crest line of moraine. Qsw an erosive stream and created erosional (strath) terraces that have boulder lags is loam to clay loam; yellow brown where oxidized, gray where unoxidized. Clast Qsd Qsld Qtsd at the surface. rock types include carbonate, crystalline rock, a moderate to large proportion Minor linear ridges—Discontinuous ridges that are generally less than 15 feet Qdb high. Visible in areas of thin supraglacial debris. Texture varies from till Qoh of shale (30Ð50 percent), and some lignite. The Antelope-phase ice margin is 59 Chetamba Qoh Qssd otherwise indicated by deposits of ice-marginal and ice-supported streams that is slightly coarser than is found in surrounding area to sand and gravel. Qlb PLEISTOCENE Qtfd Qlb Qsd Chaotic and collapsed deposits. Interpreted to be sediment localized by low Qssd DEPOSITS OF THE BIG STONE PHASE OF THE RED RIVER LOBE (Antelope Hills and Big Tom hills ice-supported-stream ridges; map unit Qssd; 75 Qtsd Creek areas, such as crevasses and supraglacial stream channels, in the disintegrating Qssd (LATE WISCONSIN) see also Fig. 2). Qdb Qtfd Boyd Qoh Qtmd Till modified by slope processes—Till along the slope of the Coteau des Prairies glacier and along the ice margin. Qsld Qtfd Qtbr Till of the Big Stone moraine—Till that contains lenses of sorted sediment and 212 MINNESOTA Qsd Qsd (a glacial erosional scarp); modified by slope wash, mass movement, and ice- Steep-sided mound of sorted sediment (kame)—Stream sediment deposited Qtfd T. 116 N. blocks of incorporated clayey lake sediment. Till texture and lithology are highly T. 116 N. Qssd marginal streams. Matrix texture is loam to clay loam; yellow-brown where on, beneath, or along wasting ice that subsequently collapsed as the ice melted. Qtmd Qoh variable. Texture of the till matrix is loam to clay; yellow-brown where oxidized, Qsld oxidized, gray where unoxidized. Clast rock types include carbonate, crystalline Circular depression—Small, generally circular pit that may contain water, lake Qtfd gray where unoxidized. Clast rock types include carbonate, crystalline rock, shale Qssd Qlh Qtfd rock, a low to moderate proportion of shale (10Ð20 percent), and some lignite. Qoh Qdb Qssd Qssd (from none to 50 percent of the coarse sand fraction), and some lignite. sediment, or peat, depending on the local water-table elevation. Interpreted RIVER In the map area, this part of the Coteau slope was exposed after the Gary phase Qtfd Qtld The unit is a complex of tills that were deposited along ice fronts that advanced to have formed through melting of buried chunks of ice. Very common in PA of the Des Moines lobe, but older units, including preÐLate Wisconsin units, Qtfd into glacial Lake Benson (Figs. 1b and 2). The first advance to this position certain parts of the Big Stone moraine. Qsd may be exposed locally. Qssd Renville was probably of the Des Moines lobe, but the later advances were of the Red Qsd Qsld Qdb Qoh Qthd Hummocky till—Till that has an irregular surface expression and contains ACKNOWLEDGMENTS Granite Falls River lobe. Although the Red River lobe followed a path similar to that of the Qtld Clarkfield Qtfd 212 discontinuous lenses of clay, silt, sand, and gravel. Clast rock types include Qtad Qsh Qoh 67 67 Field work was conducted by Carrie J. Patterson, Alan R. Knaeble, Sara E. Gran, and Minnesota Des Moines lobe, its clast content and pattern of retreat indicate it originated in Qlb carbonate, crystalline rock, a low to moderate proportion of shale (10Ð20 percent), Stephanie J. Phippen; additional assistance in the field was provided by Thomas Hooyer, Tammy Falls H Qsd a different part of the ice sheet (directly north rather than northÐnorthwest of Qtfd aw Sacred Heart and some lignite. Unit is interpreted to have been deposited during the Altamont Rittenour, and Heather Anderson. Terrence J. Boerboom mapped bedrock outcrops. The data Qtmd k

the study area; Figs. 1a and 1b). The unit includes areas where lobate bodies of Qsld Creek and Gary phases of the Des Moines lobe on and beneath stagnant, wasting ice, base was compiled by Barbara A. Lusardi and Emily J. Bauer; wells were located in the field Qthd till, interpreted as flow tills, extend from the position of the former ice front (along T. 115 N. Qsd Cre T. 115 N. and it may have been subject to repeated mass movement during deposition. Qoh the Big Stone moraine) into glacial Lake Benson (shown on map by fan symbol). by Tammy Rittenour, Angela Whitney, Heather Anderson, Eric Olsen, and Stacy Foss. Canoe Creek Qsh ek Qoh Lake Unit includes small areas of supraglacial lake and stream sediment. Much of support was provided by Philip Heywood. Special thanks are owed to the staff at the Upper Qssd Louie Qtfd Arcuate ridge crests mark the eastern extent of the moraine (crest line of moraine Qtfd ° the relief is inherited in the northeast corner of the map area: the till there buries Sioux Agency State Park (especially Terri Dinesen) and Lac qui Parle State Park for their friendly 44°45' 44 45' symbol; see Description of Map Symbols); they may be small push moraines. Qsld Hazel Run Heart an older moraine of an ice advance from the northeast, and the till texture reflects assistance. The staff at the Minnesota Department of Natural Resources fisheries office in Qlb Elsewhere, the moraine has an irregular, extremely pitted surface, and the till Qtfd Qsd Qoh the more sandy till of the underlying Alexandria moraine (Alexandria highlands; Qoh Qtsd Qlb contains many boulders. Pits are interpreted to have formed by burial and Ortonville provided access to the outcrops on Big Stone Lake. Retired soil scientist Raymond QsdCanby 23 Qtfd Fig. 2). Diedrick shared unpublished information on glacial Lake Benson. David Craigmile, local resident Lazarus er Sacred subsequent melting of small blocks of ice, possibly lake ice. Boulders are Qssd Riv Qlb Qsd Stream sediment—Sand and gravel deposited by meltwater issuing from stagnating and amateur geologist, contributed observations, interest, and encouragement. J.F.A. Cotter, 68 Creek interpreted to have been incorporated locally from nearby granite outcrops. Linear Qtsd ing Qsw or receding ice of the Altamont and younger phases of the Des Moines lobe. Qtad Spr depressions trending south and southeast through the moraine are interpreted to A.C.R. Campos, H.E. Wright, Jr., and C.L. Matsch provided valuable comments in the field. Qsd Includes sediment of contemporaneous nonglacial streams, as well as younger Medicine Creek represent collapsed drainageways that eroded through or beneath debris-laden ice. Qsd Qlb and finer glacial and postglacial stream sediment. Broadly arcuate streams delimit Qsd llow Lake Qtfr Till with stream-modified surface—Till modified by flowing water; fluvially eroded SELECTED BIBLIOGRAPHY Qtfd Qsld Ye Qtfd Wood Wood former ice-margin positions (Marshall phase, Antelope phase, and possibly younger River and streamlined in places. Till texture, lithology, and color are as above (till of Brug, W.H., Jr., 1982, Soil survey of Chippewa County, Minnesota: U.S. Soil Conservation Lake Qsld phases). Yellow Medicine Qtfd Qsd the Big Stone moraine; map unit Qtbr). Locally overlain by thin lag of sand and Service, 132 p., 91 fold-out maps. Qtsd Hanley Qoh Qssd Stream sediment formerly supported by ice—Ridges of sand and gravel deposited Qlb PA Parle Qtfd Qsw gravel or covered by silt and clay. Channel scars are common; channels may Diedrick, R.T., and others, 1973, Soil survey of Swift County, Minnesota: U.S. Soil Conservation Qtfd Qsd Falls Qlh by streams; some glacial sediment was deposited by gravity flow into channels. Qsd Spellman Qlb Qoh T. 114 N. Qsd Lake T. 114 N. localize organic deposits (map unit Qoh), lakes, and modern streams and flood Service, 116 p., 88 fold-out maps. ek Interpreted to have been deposited in channels that were walled, supported, or Qtfd Qlh Qlh Qsld re waters. Stipple indicates areas that collapsed after stream modification, probably Qthd Mud C Diers, M.P., 1995, Soil Survey of Big Stone County, Minnesota: U.S. Natural Resources Qthd Lacqui Qssd Qsh enclosed by ice (eskers in the broadest definition of the term). Melting of ice Qoh Qtfd Qoh from meltout of buried ice; the resulting topography is irregular. Conservation Service, 171 p., 44 fold-out maps. Cr Wood pring may have led to local disruption of bedding. A significant amount of unsorted, ee Qtfder S Hokanson, H.L., 1978, Soil survey of Lyon County, Minnesota: U.S. Soil Conservation Service, Qgl Qsld k Riv Lake Qsh Qsd Qdb DEPOSITS OF THE ALTAMONT, MARSHALL, GARY, ANTELOPE glacial sediment may overlie the sorted sediment. Areas of this unit too small Qgl 149 p., 60 fold-out maps. Porter icine Boiling AND YOUNGER PHASES OF THE DES MOINES LOBE (LATE WISCONSIN) to delineate at the map scale are indicated by a line symbol (minor linear ridges; ed Qoh ———1981, Soil survey of Yellow Medicine County, Minnesota: U.S. Soil Conservation Service, Qssd M see Description of Map Symbols). Qgl Qoh Cottonwood Qlh Qlb Lake sediment of glacial Lake Benson—Silt, clay, and some fine sand; rhythmically Qtmd Lake 203 p., 59 fold-out maps. Sham laminated in places. Upper part of unit is commonly a massive silt. The thickest, Qsld Stream sediment overlain by lake sediment—Similar to stream sediment (map Lake Hokanson, H.L., and others, 1971, Soil survey of Lincoln County, Minnesota: U.S. Soil Qtfd Qlh Qoh most continuous lake sediment is found in the northeastern quadrant of the former unit Qsd) but buried by thin layers (generally less than 10 feet thick) of clay, Qsh Qtfd Echo Conservation Service, 84 p., 90 fold-out maps. Qsd silt, fine sand, and organic deposits. Streams flowing down the Coteau des Prairies Yel lake, where the lake may have survived longer after the southern part of the low Tyson Leverett, F.L., with contributions by Sardeson, F.W., 1932, Quaternary geology of Minnesota 59 Qtfd Lake basin was drained. A discontinuous distribution of lake sediment in lake margins, slope deposited fans (for example, Canby fan; Fig. 2) that blocked streams flowing Qsd Qssd Qtsd 67 and parts of adjacent states: U.S. Geological Survey Professional Paper 161, 149 p., 5 pls. QsdLincoln Cottonwood Belview Taunton nch Qsd ice-supported inlets and outlets, and a lack of clear shoreline features indicate southeast between the base of the slope and the ice margin. The unit is also ra Qtfd in pocket B present where glacial streams backed up owing to some other type of constriction. Qtfd Qssd Qoh that the lake was confined by stagnant ice. Minor linear ridges and small channels Matsch, C.L., 1972, Quaternary geology of southwestern Minnesota, in Sims, P.K., and Morey, T. 113 N. Qsd Lady Slipper Qtfd Qgl Qoh Lake Qtsd in the basin are interpreted to have formed beneath stagnating ice. Stipple indicates Qgl Sediment of ice-walled glacial lakes—Lake sediment in a high topographic position. Qthd Qsld T. 113 N. G.B., eds, Geology of Minnesota: A centennial volume: Minnesota Geological Survey, p. 68 Curtis areas of collapsed lake sediment, which is interpreted as originating from meltout Deposited in pools in stagnant ice. Fine sediment (clay and silt) may be Qgl 75 Lake 548Ð560. Qgl outh rhythmically bedded near former lake centers; minor amounts of sand and gravel S Qlh of buried ice; the resulting topography is irregular. Matsch, C.L., and H.E. Wright, Jr., 1967, The southern outlet of Lake Agassiz, in Mayer-Oakes, Qoh are present along former lake rims. Unit commonly contains thick, till-like, debris- 271 Qoh Qdb Delta sediment of glacial Lake Benson—Sand, gravel, and silt deposited by streams W.J., ed., Life, land and water—Conference on environmental studies of the Glacial Lake Qsld Lyon Qoh Qsh flow deposits. Forms flat-topped circular uplands within hummocky till terrain Qsd Qssd Minneota Qsld Qoh Qssd entering glacial Lake Benson. The largest deltas formed at the mouths of the Agassiz region, 1966, Proceedings: Winnipeg, University of Manitoba, Department of Qthd River School Grove in the southwest and northeast corners of map area. Qgl Qtfd Lake Pomme de Terre and Chippewa Rivers. Minor deltas are located (1) on the Anthropology Occasional Paper 1, p. 121Ð140. 23 67 19 northeastern side of the basin where the East Branch Chippewa River entered Murray, J.J., 1985, Soil survey of Redwood County, Minnesota: U.S. Soil Conservation Service, Steep Qsh Redwood PROTEROZOIC AND ARCHEAN Bank Qtfd Qlh Qlh it (Swift Falls delta; Fig. 2); (2) at a higher elevation south of the East Branch Lake Qsd Qoh PA Gneiss and granite, undivided—Archean quartzofeldspathic gneiss; granitoid 166 p., 69 fold-out maps. Qgl Qtfd Chippewa River where some small streams entered during a higher stage of the Setterholm, D.R., project manager, 1995, Regional hydrogeologic assessment, Quaternary geology, Medicine Qtsd intrusions and low-grade greenstone belts. Exposed mostly along the bottom T. 112 N. Qgl Qsd Perch Qoh Qtsd Qsd Qsd T. 112 N. lake (within the Kerkhoven washed-till plain; Fig. 2); and (3) where Tenmile Lake Qssd 19 of the Glacial River Warren channel (present-day Minnesota River Valley), where southwestern Minnesota: Minnesota Geological Survey Regional Hydrogeologic Assessment Yellow Qthd Qtfd Qsd Creek entered the southwest part of the basin (Boyd delta; Fig. 2). Stipple indicates Lake Qsd Ghent Qtfd Qsd Series RHA-2, Part A, 2 pls., scale 1:200,000. Hendricks Qoh Vesta overlying glacial sediment and weathered rock (saprolith) have been eroded. Hendricks Qtmd Qtmd Qsh Qsd collapsed delta sediment, areas where a delta apparently formed on a buried glacier Tufvesson, Dave, 1997, Soil survey of Lac qui Parle County, Minnesota: U.S. Natural Resources Qgl Qthd 44°30' Saprolith is still preserved in some protected locations. The smoothly undulating 44°30' and possibly on lake ice; the resulting topography is irregular. ° ° R. 37 W. 95°15' rock surface is interpreted to have formed through chemical weathering while Conservation Service, 1 case (2 pts., 61 folded pages of maps). R. 46 W. R. 45 W. 96 15' R. 44 W. R. 43 W. 96°00' R. 42 W. R. 41 W. 95°45' R. 40 W. R. 39 W. 95 30' R. 38 W. Qtsd Subglacial till—Dense, homogeneous till of the Marshall, Antelope, and younger GIS compilation and cartography by the rock was buried by thick regolith. Glacial and fluvial erosion selectively Digital base modified from 1990 Census TIGER/Line Files phases of the Des Moines lobe. Texture of till matrix is loam to clay loam. Every reasonable effort has been made to ensure the accuracy of the factual data on which this map interpretation is SCALE 1:200 000 Joyce Meints and Philip Heywood stripped away the regolith but has made only the minor modifications to the rock of U.S. Bureau of the Census (source scale 1:100,000); Clast rock types include carbonate, crystalline rock, shale (average proportion based; however, the Minnesota Geological Survey does not warrant or guarantee that there are no errors. Users may 5 0 5 10 MILES surface of striae, crescentic fractures, polish, and potholes. wish to verify critical information; sources include both the references listed here and information on file at the offices of county border files modified from Minnesota Department of the Minnesota Geological Survey in St. Paul. In addition, effort has been made to ensure that the interpretation Transportation files; digital base annotation by Minnesota 5 0 5 10 15 KILOMETERS conforms to sound geologic and cartographic principles. No claim is made that the interpretation shown is rigorously Geological Survey correct, however, and it should not be used to guide engineering-scale decisions without site-specific verification. Universal Transverse Mercator Projection, grid zone 15 1927 North American Datum

Pomme de Terre spillway 96° 96° BIG STONE D e Big Stone moraine s deltaAlexandria M EXPLANATION o highlands lo i ne b n River Red Alexandria highlands—High-relief morainic topography created by earlier Glacial Lake Benson delta—Sediment deposited where streams, mainly Big Sto ) e e be s Swift Falls ice advance of northeast-source lobe; overridden by Des Moines lobe the Pomme de Terre and Chippewa, entered glacial Lake Benson. lo lobe ed River 97° 96° 95° (R ° ° UPPER Glacial with minor effect. Boyd delta—Deposited where a glacial stream entered glacial Lake 46 46 Big Stone N. DAKOTA MINNESOTA Lake Agassiz River Warren gorge Hummocky highlands—Ice-stagnation topography. Thick, hetero- Benson. An older, ice-supported delta is offshore; a delta of yet another 45°00' Glacial Lake Benson delta GRANT DOUGLAS Swift RIVER A. Ice margins of Kerkhoven geneous supraglacial deposits. Mostly map unit Qthd. lake stage is present southward, near Clarkfield. A the Des Moines washed- Coteau slope—Northeast-facing slope of Coteau des Prairies (glacial Pomme de Terre scour—Scour surface is traceable to mouth of Pomme n BASIN t EXPLANATION el lobe: B, Bemis; Big Stone B. The Big Stone moraine— C. Glacial Lake till plain erosional scarp). Mostly map unit Qtmd. de Terre spillway; large, erosive flow of water that created scour is TRAVERSE op Big Tom hills SWIFT M e Gary ice-marginal-stream slope—Stream-washed till and collapsed also responsible for draining south part of glacial Lake Benson. Main Testhole—Recovery of continuous, a An Alt, Altamont; moraine which initially formed Agassiz and STEVENS POPE rs ice-walled- CHIPPEWA four-inch-diameter core of Quater- ha stream sediment along upper parts of Coteau des Prairies slope. The scour-created channel probably obscured by current channel of G ll G, Gary; during the Big Stone Glacial Glacial River a M stream ridges streams were confined by ice on northeast margins of channel (kame Minnesota River. Secondary scour channel is now occupied by BIG nary sediment to a depth of about ry M, Marshall; phase of the Red River River Warren. Glacial ° terrace). Mostly map units Qtfd and Qssd. Chetamba Creek. 200 feet. 44 30' Pomme de Terre scourLake Benson STONE A An, Antelope. lobe—and glacial Lake Warren Benson draping l Marshall till plain—Flat-lying till plain of Marshall phase of the Des Pomme de Terre spillway—Uncommonly straight spillway that originated t G Glacial SWIFT Sample site, cuttings—Sediment a Benson. As many as two plain Chippewa m Glacial Moines lobe. Subglacial till (map unit Qtsd) is locally overlain by thin, far north of map area (Pelican Rapids); main contributor to delta at Minn. collected during the drilling of a o Lake Benson n Alt Lake Benson later advances also 45° ° patchy, supraglacial till. north end of Lake Benson. B t 45 Minnesota River water well or other type of drillhole. 45° ° e reached this limit. plain 45 m Canby fan—Deposited at base of Coteau des Prairies by stream flowing Benson draping Pomme de Terre scour—After the Pomme de Terre CHIPPEWA Sample site, soil boring—Auger is Pomme de Terre scour downslope (shown by fan symbol on map unit Qsd). Such fans caused scour channel formed, the northern part of glacial Lake Benson basin 45° LAC QUI KANDIYOHI 45° PARLE depth generally less than 20 feet. V B Redwood Cottonwood occasional ponding of southeast-flowing streams that ran parallel to refilled with water. It eventually drained south along channels now ° e 44 00' r d till plain Coteau base. occupied by Sacred Heart Creek, Hawk Creek, and other southerly, Sample site, outcrop—Natural and Lac qui Parle i artificial Quaternary exposures; Figure 1. Sequence of glacial events in western Minnesota during the Late Wisconsin. Redwood ice-marginal-stream flats—Formed by glacial streams flowing subparallel streams. RENVILLE SOUTH- RENVILLE YELLOW MEDICINE includes temporary excavations. Antelope Hills along margin of Des Moines lobe during Marshall and Antelope phases Kerkhoven washed-till plain—Low-relief till surface that eroded during WESTERN The Laurentide ice sheet was in steady decline as the Des Moines indicates that the lake was overwhelmed by meltwater from the Pomme Boyd of the Des Moines lobe. early high stage of glacial Lake Benson, probably while ice remained Borehole geophysical log—Read- ice-walled MINNESOTA lobe was advancing, and each readvance was therefore less extensive de Terre River, which may have been a spillway from another glacial LAC QUI PARLE delta Big Tom hills ice-walled-stream ridges—Formed by ice-supported in basin. Concentration of deltas and linear features interpreted as ings taken from a water well or Renville stream ridges Glacial other kind of drillhole. than its predecessor (A). Ice margins of the phases may be marked by lake north of the study area. The flow from the Pomme de Terre may YELLOW MEDICINE Lake Benson glacial streams flowing near ice margin during Marshall, Antelope, shorelines mark stable lake level (indicated by a dashed line on figure). LINCOLN LYON REDWOOD 43°30' and possibly younger phases of Des Moines lobe. Streams may have Swift Falls delta—Sediment deposited where streams cutting through 96°00' 95°15' moraines, belts of hummocky topography, and ice-marginal-stream ultimately have caused the drainage of glacial Lake Benson. (Lake plain Canby fan been walled by ice, floored and walled by ice, or have flowed in ice Alexandria highlands entered glacial Lake Benson from northeast. channels. Benson as shown in B is smaller than was its original area, which tunnels. Big Stone moraine—Hummocky moraine formed by Red River lobe as i ICE MARGINS IN ce Antelope moraine S O U T H D A K O T A T A K O T H D S O U Yellow Medicine Glacial Lake Benson formed as the Des Moines lobe receded from extended an unknown distance north.) -m Antelope Hills ice-walled-stream ridges—See Big Tom hills. it advanced into glacial Lake Benson. Contains abundant small, circular ar PIPE- COTTON- SOUTHWESTERN gi Antelope moraine—Short moraine segment marks Antelope phase of pits, some arcuate moraine crests, and small lobes of flow till that MURRAY the lowland now occupied by the Minnesota River (B). The Red River Lake Agassiz (C) formed when the Red River lobe receded north Coteau na STONE WOOD l-s Des Moines lobe (map unit Qtad). protrude into area of lake. 44° 44° tr ° MINNESOTA of the Big Stone moraine. This extremely large lake drained from its e 97° 96 95° lobe advanced from the north to the position of the Big Stone moraine LINCOLN am LYON Cottonwood till plain—Flat-lying till plain of Antelope and younger phases River Warren gorge—Deep, straight trench created by drainage of the Lincoln slope fla [The two areas represented are the regional and into Lake Benson. The history of this lake, which was dammed southern tip for much of its existence, creating the River Warren spillway, ts Cottonwood till plain of Des Moines lobe. Subglacial till (map unit Qtsd) locally overlain extremely large Glacial Lake Agassiz that formed behind Big Stone 0 50 mi hydrogeologic assessments for the upper Hummocky Lyon by stagnant ice, is complex. The advance of the Red River lobe into which followed the same general route as the drainage from glacial Lake by thin, patchy, supraglacial till. moraine. Redwood Minnesota River basin (this map) and highlands REDWOOD Glacial Lake Benson plain—Flat-lying lake plain created when meltwater 0 80 km the basin decreased the basin area and may have raised lake levels Benson. southwestern Minnesota (Setterholm, from wasting Des Moines lobe, with contributions from various inlets, ° 1995). All the margins are of the Des temporarily and (or) contributed to drainage. The scoured lake bottom 96 could not be drained efficiently through stagnant, debris-rich ice of 96° Gary ice-marginal- Marshall till plain LOCATION OF MAP AREA Moines lobe, except the Big Stone margin Antelope-phase margin. 0 10 20 30 mi of the Red River lobe.] stream slope 0 10 20 30 mi 0 10 20 30 40 km 0 10 20 30 40 km DISTRIBUTION OF THE PRINCIPAL SOURCES OF GEOLOGIC DATA Figure 2. Geomorphic regions of the upper Minnesota River basin. The regions in the explanation are ordered by age, beginning with the oldest. IN THE UPPER MINNESOTA RIVER BASIN The symbol indicates two areas of the same geomorphic type, one of which is unlabeled due to lack of space. ©1999 by the State of Minnesota, Department of Natural Resources, and the Regents of the University of Minnesota REGIONAL HYDROGEOLOGIC ASSESSMENT The University of Minnesota is an equal opportunity educator and employer QUATERNARY GEOLOGY — UPPER MINNESOTA RIVER BASIN, MINNESOTA Prepared with Support from the REGIONAL HYDROGEOLOGIC ASSESSMENT RHAÐ4, PART A MINNESOTA GEOLOGICAL SURVEY MINNESOTA DEPARTMENT OF NATURAL RESOURCES, DIVISION OF WATERS Plate 2—Quaternary Stratigraphy D.L. Southwick, Director Figure 6. UMRB-1 (SW1/4 NW1/4 sec. 34, T. 117 N., R. 46 W., Lac qui Parle County) ° ° ° 96 30' 96°15' 96°00' 95°45' 95°30' 95°15' 96 30' 96°15' 96°00' 95°45' 95°30' 95°15' 96 30' 96°15' 96°00' 95°45' 95°30' 95°15' Coarse Sand Grain Counts QUATERNARY STRATIGRAPHY 900 Matrix Texture Gamma Log Lithologic Description and Interpretation Precambrian:Paleozoic:Cretaceous 0 850 0 75 0 0 80 850 800 9 750 0 0Ð9 ft Diamicton, light olive brown; upper 5 ft is clast-poor and has a silt matrix; secondary By EXPLANATION 850 9 55 : 29 : 16 50 gypsum at 4Ð5 ft; below 5 ft the matrix is a clay loam. Unnamed till Thickness of sediment in feet 900 9 00 9 0 0 0 9Ð18 ft Diamicton, loam matrix, variable to olive brown in color; sharp upper contact, although Carrie J. Patterson, Alan R. Knaeble, Dale R. Setterholm 75 42 : 25 : 33 similar to overlying till; abundant shale clasts; sandy and gravelly towards base. Till unit 4 45°15' 45°15' < 50 ft 45°15' 9 50 9 8 50 Minnesota Geological Survey 00 650 0 8 700 0 750 18Ð29 ft Sandy loam; gray; laminated in places. Lake sediment

0 1075 50Ð100 ft 5 8 29Ð36 ft Diamicton, loam to sandy clay loam matrix, black; below 33 ft becomes denser, 25 James A. Berg 1 0 00 more uniform and fissile, with a clay loam to loam matrix; includes Cretaceous non-Pierre 42 : 27 : 31 900 850 950 100Ð150 ft 0 Shale clasts (probably Fairport Mbr. of Carlile Fm.). Unnamed supraglacial or glaciolacustrine Minnesota Department of Natural Resources 0 800 9 00 00 till 10 8 0 0 0 1999 150Ð200 ft 1 850 36Ð61 ft Diamicton, clay loam matrix; dense and uniform; very dark gray to black; fissile in 0 52 : 17 : 31 0 80 places; clasts include Cretaceous concretions and shells. Unnamed till (not till unit 4) 0 0 9 1050 1 00 200Ð250 ft 9 5 0 50 61Ð62.5 ft Medium sand grading up to fine sand; dark gray to dark gray brown. INTRODUCTION 45°00' 45°00' 45°00' 00 850 Stream sediment 1 0 250Ð300 ft 9 50 62.5Ð63.5 ft Fine sand and silt with scattered clasts; mottled. Lake or stream sediment This plate provides an interpretation of the depositional setting, distribution and relative 9 0 85 : 12 : 03 age of stratigraphic units documented from subsurface data and surficial mapping (Plate 1) 300Ð350 ft 900 0 63.5Ð68 ft Diamicton, loam to sandy clay loam matrix; light olive gray. Till unit 7 8 50 in the upper Minnesota River basin area. The stratigraphic framework (Table 1) allows 9 1025 800 00 68Ð72 ft Diamicton, clay to clay loam matrix, dark gray to black, contains waxy dark shale 350Ð400 ft 1000 62 : 23 : 15 one to predict where certain units will be encountered, based on their known distribution 0 clasts; sharp contact with overlying unit; silt stringers present throughout; thin fine sand and 9 50 0 850 75 9 11 00 silt layer near base; basal 1 inch is sheared. Unnamed subglacial till and on the nature of the geologic processes that formed them. The stratigraphic framework 9 75 800 5 7 0 0 0 0 400Ð450 ft 1 1 5 0 facilitates exploration for targets such as subsurface aquifers. This plate includes a digital 000 9 72Ð75 ft Diamicton, silty clay loam to clay loam matrix; light gray to dark gray; calcareous. 1 50 0 9 1 0 800 98 : 02 : 00 0 elevation model (Fig. 1), a map showing the thickness of glacial sediments (Fig. 2), and a 950 00 700 Unnamed till 44°45' 44°45' 450Ð500 ft 750 44°45' model of the bedrock elevation (Fig. 3). Figure 4 shows the location of subsurface stream 75Ð93.5 ft Silt with clay and fine sand, coarsens upward; includes shells, and some pebbles; 1050 850 0 1000 0 0 sediment associated with till units 5 and 6, and Figure 5 shows the location of subsurface 0 9 at 84.5 ft it is slightly coarser, more oxidized, and contains clay intraclasts in silt; at 92 ft the 0 1 0 0 0 500Ð550 ft 0 0 1 0 9 100 sediment grades down to a very clayey and dense unit. Lake sediment stream sediment associated with Till units 7, 8, 9, and 10. The index map shows the 5

850 0

1050 1 0 0 location of the three cross sections (AÐA', BÐB', and CÐC') and the three continuous cores 2 950 93.5Ð95 ft Diamicton, silty clay matrix; dark grayish brown; chalk clasts, large shale clasts, 550Ð600 ft 1 900 99 : 01 : 00 0 1 0 950 0 numerous Precambrian grains. Unnamed till (Figs. 6, 7, and 8). The essential characteristics of the 11 till units are given in Table 1, and 0 11 0

0

0 the relative age of lake and stream sediments, and soil horizons or organic deposits is 600Ð650 ft 2 10 0 0 95Ð100 ft Coarse sand with pebbles; dark grayish brown to light olive brown; grus-like 1 1 0 10 50 0 1 50 indicated. 1150 00 0 0 composition; contains no mafic, metasedimentary, sedimentary or carbonate grains. 98 : 02 : 00 0 1 975 1150 5 1 1 Data used to develop the stratigraphic interpretation shown here include the three 1 Leached stream sediment 44°30' 44°30' 44°30' 125 continuous cores that were drilled for this project (UMRB-1, 2 and 3, Figs. 6, 7, and 8), Clay 100Ð105.5 ft Gravel; calcareous; basal contact is a sharp erosion surface. 76 : 24 : 00 Unleached stream sediment water-well records, cuttings from rotary drill holes, gamma logs of wells and holes drilled sea level) above (feet Elevation

Figure 1. Digital elevation model of land surface. Shaded relief is portrayed using U.S. Figure 2. Thickness of Quaternary sediment. The sediment between the land surface and bedrock Figure 3. Bedrock elevation, extent of Cretaceous bedrock, and distribution of subsurface surface) ground below Depth (feet for scientific purposes, as well as shallow auger holes, and the multi-till outcrops present 105.5Ð117.5 ft Diamicton, clay loam to loam matrix; gray brown to dark gray; calcareous; Geological Survey 90-meter grid cell digital elevation data. The model has 940 ft of overall surface is mostly of glacial origin. Thickness was determined by subtracting the gridded bedrock- stream sediment greater than 20 ft thick at the base of the Quaternary units. Bedrock elevation 54 : 46 : 00 along tributaries to the Minnesota River (see figure on Plate 1 for data location). These contains blocky shale clasts and yellow orange-stained carbonate clasts. Till unit 8 relief, with a maximum grid elevation of 1790 ft in the southwest corner of the study area. elevation data (Fig. 3) from the gridded land-surface digital elevation data (Fig. 1). The sediment is contoured in 50-ft intervals. The gray stipple shows the extent of Cretaceous bedrock. Stream data are of varying quality. Outcrops are the best source of information because the 950 thickness data were then contoured with a 50-ft interval. Bedrock outcrop is shown in black. deposits that are well constrained by existing data are indicated by solid lines. Stream deposits 117.5Ð120.5 ft Diamicton, silty clay loam to clay matrix; olive brown; upper and lower contacts continuity and context of the units can be directly observed. A few outcrops such as those Silt 150 Quaternary sediment is thinnest (<50 ft, white) in the upper Minnesota River Valley, which that are poorly constrained by existing data are indicated by dashed lines. The bedrock surface marked by thin black silty zone (possibly a soil or reworked fines); numerous lenticular white 45 : 55 : 00 along the Yellow Medicine River and Hawk Creek near their confluence with the Minnesota zones (marl); silty clay near lower contact. Flow till or glaciolacustrine facies of till unit 8 marks the axis of the most recent advances of the Des Moines lobe. Quaternary sediment is elevation model was created using data obtained from water-well construction, scientific test River include many or most of the tills recognized. The continuous cores (Figs. 6, 7, and 120.5Ð123.5 ft Silty clay loam; very dark gray; locally carbonate-rich. Lake sediment 96°30' 96°15' 96°00' 95°45' 95°30' 95°15' thick (600Ð650 ft) in the southwest where Des Moines-lobe deposits overlie a thick sequence of drilling and bedrock outcrops. Bedrock mainly crops out along the Minnesota River Valley. 8) provide deep (as much as 225 ft below the land surface) stratigraphic information away 980 ft older, pre-Wisconsinan glacial sediment that forms the Coteau des Prairies. Quaternary sediment The bedrock elevation data were interpreted and a geomorphologically probable surface was 123.5Ð129 ft Diamicton, clay matrix with polished pebbles; olive brown; contains secondary from the Minnesota River, although the nature of the contacts and the continuity of the MINN. 60 : 32 : 08 is also thick in the northeast were the Des Moines lobe deposits overlie sediments of the Alexandria contoured. The model exhibits 665 ft of overall relief, with a maximum elevation of 1285 ft 925 carbonate on fractures; strongly oxidized. Unnamed till units is not as easily discerned. Gamma logs are useful for identifying sandy units, some Moraine. and a minimum elevation of 620 ft. In areas to the southwest the uppermost bedrock is Cretaceous 175 129Ð158 ft Diamicton, clay loam matrix, with silty clay loam and silt loam; black to very dark till-till contacts and the contact between glacial sediments and bedrock. Water-well records in age. Elsewhere, Cretaceous-age rock was either not deposited or was eroded prior to or Sand grayish black; variably oxidized; calcareous throughout; snail shell and wood at 137.5 ft; 53 : 45 : 02 also assist in distinguishing sandy from non-sandy units, as well as in identifying coloration 980 ft lighter gray below 141.5 ft; shark tooth at 148.5 ft; sharp basal contact. Unnamed till 980 ft during the Quaternary, and the first bedrock encountered is Precambrian in age. These areas of associated with oxidized zones (which may represent units formerly at the land surface), 45°15' 995 ft Precambrian rock may be deeply weathered (weathering took place prior to the late Cretaceous) 158Ð199 ft Fine to coarse sand; grayish brown; calcareous throughout; 80 percent quartz and allowing an interpretation of the depth to bedrock. Cuttings from rotary drilling provide 96°30' 96°15' 96°00' 95°45' 95°30' 95°15' grains; scattered pebbles at 181 ft; at 186 ft it is a medium to coarse sand with local Appleton so that saprolite (deeply weathered rock) is encountered at the elevations indicated here, and 90 : 10 : 00 information about the general lithology and approximate contacts of subsurface units, but 920 ft 900 concentrations of black granules (lignite?); below 186 ft it is a coarse sand with polished and 935 ft unweathered rock is only found at greater depths below the bedrock surface. The bedrock mixing during the drilling process results in the cuttings becoming increasingly unreliable 985 ft 960 ft 990 ft 940 ft rounded pebbles. Stream or delta sediment 940 ft surface contoured here was not necessarily ever completely exposed at the land surface. The 200 with depth. dendritic network of stream sediments documented in areas of lower elevation (shown with 199Ð201 ft Diamicton, silt loam matrix; very dark gray. Unnamed till 61 : 38 : 01 Past glaciations had global effects, and one can use information from a variety of sources 925 ft heavy solid and dashed lines) indicate that at least the central corridor (about two-thirds of the 201Ð204 ft Gravel, silt matrix, some matrix support; below 202 ft it is almost clast-supported. to interpret glacial events. Ocean sediments and ice cores provide evidence for numerous 44 : 51 : 05 mapped area) was exposed at the surface. Gravelly till or silty gravel sieve deposit glacial periods during the Pleistocene Epoch. The Upper Midwest was directly affected 990 ft 45°15' 960 ft 875 204Ð218 ft Sand, fines upward from medium to coarse sand to fine sand with silt; gray; by ice during at least three of the ten most recent glacial periods during the last 800,000 935 ft 81 : 19 : 00 45°00' 920 ft calcareous throughout. Stream or delta sediment 990 ft 225 years (Table 1). During any glacial period, many ice lobes can flow into an area, and each Appleton 0 20406080100 0 4080120 59 : 40 : 01 lobe may have multiple advances. For example, surficial sediments together with the 970 ft Cumulative % API gamma units 218Ð219 ft Diamicton, loam matrix; gray. Unnamed till Table 1. General description of major stratigraphic units 219Ð225 ft Shale; dark; waxy. Cretaceous bedrock Quaternary stratigraphy show that during the last glaciation the upper Minnesota River 950 ft 925 ft basin was affected by the Red River lobe and the Des Moines lobe. These ice lobes did not 1,000 ft simply advance and retreat. Quaternary sediments indicate that they show complex patterns Sedimentary Texture Composition, Location, Correlation, Possible 975 ft 925 ft Figure 7. UMRB-2 (NE1/4 NE1/4 sec. 18, T. 122 N., R. 46 W., Big Stone County) including multiple advances, stagnations, and retreats. The oscillations of the Des Moines 940 ft Unit Grain-Count Data Ice-lobe affiliation Age 940 ft lobe alone indicate four distinct ice margins in the area—the Altamont, Gary, Marshall, 45°00' B Till unit 1 Clay 21Ð25%; Trace or no Cretaceous shale; Present in Big Stone moraine Coarse Sand Grain Counts e ≤ and Antelope ice margins (Plate 1). There are probably three to five more ice margins d sand = silt Precambrian Paleozoic Matrix Texture Gamma Log Lithologic Description and Interpretation Precambrian:Paleozoic:Cretaceous r ° oc 44 45' between the Antelope ice margin and the Big Stone moraine in the north of the area mapped. k e leva Till units tion 1, 940 ft Till unit 2 Clay 22Ð29%; Cretaceous shale 15Ð30%; Present in Big Stone moraine; 1100 0 0Ð5 ft Pebbly silt; dark grayish brown; organic-rich; calcareous; weakly laminated. The Des Moines lobe therefore had the potential to stack as many as seven to nine similar 050 995 ft 960 ft ft grouped sand ≤ silt Precambrian = Paleozoic may correlate to St. Hilaire Fm. Holocene lake sediment tills in the region of the Big Stone moraine, with the number decreasing to the south. A on (Harris and others, 1995); 1,000 ft 46 : 54 : 00 total of five Des Moines-lobe till units has been distinguished in this study. The Red River cross a till of the Red River lobe 5Ð25 ft Diamicton, loam to clay loam matrix; soil structure in upper part; light yellowish brown B 945 ft to pale brown; non-calcareous to weakly calcareous; includes carbonate clasts, but no shale e sections lobe as well as earlier ice lobes probably behaved in a similar manner. d 0 10 20 30 mi ro Lake sediment Laminated, varved or massive silts and clays Glacial Lake Benson II clasts. Till unit 1 ck eleva Multiple advances of one ice lobe may create very similar tills. If the source area for the tion 1,000 ft 25Ð45 ft Diamicton, loam matrix; similar to overlying till unit 1, but firmer; dark gray to light ice does not change from one glacial period to the next, the tills of these glacial periods 20 40 km ° 25 0 10 30 950 ft 44 45' Till unit 3 Clay 25Ð40%; Cretaceous shale 30Ð60%; Present in the Big Stone moraine 1075 brownish gray. Till unit 2 39 : 41 : 20 will be similar, which adds to the difficulty of distinguishing between stratigraphic units. sand < silt Precambrian = Paleozoic may correlate with Dahlen Formation 10,000Ð 44°30' In the upper Minnesota River basin region most of the ice advanced from the north-northwest 960 ft 970 ft (Harris and others, 1995); 30,000 45Ð96 ft No core recovered from 45Ð66 ft. Below 66 ft: silt loam with sand and occasional a Des Moines-lobe till or north, incorporating many of the same rock types. Thus, out of the total of 11 till units yrs B.P. granule- and pebble-size clasts; finely laminated; increase in amount of pebbles and Figure 4. Subsurface stream sediment associated with till units 5 and 6. This map shows the Late granules in lower 1.5 ft. Glacial Lake Benson sediment identified in the region, only till unit 9 is from a distinctly different source area. Therefore Lake sediment Laminated, varved or massive silts and clays Glacial Lake Benson I Wisconsinan an exposure of till examined out of stratigraphic context cannot be classified on the basis distribution of known sand and gravel bodies that are at least 20 ft thick, and have surface elevations (marine 96Ð117 ft Diamicton, silt loam matrix, possible soil structure in upper part; dark gray; blocky; between 950 ft and 1000 ft. Elevations given on the map are the approximate upper surfaces of 0 10 20 30 mi 965 ft oxygen 1050 50 calcareous; below 100 ft the sediment is a dense, fairly uniform diamicton with a loam to silt 22 : 18 : 60 of field criteria alone. There is also significant overlap in the laboratory-determined criteria isotope the sediment, although this will vary along the stream course. The medium gray areas indicate Till unit 4 Clay 20Ð35%; Cretaceous shale 30Ð60%; Present in the Cottonwood Till Plain; loam matrix, and contains abundant shale granules and pebbles between 100 ft and basal (textural and grain-count data, Figs. 6, 7, and 8). Many of the units documented from 0 10 20 30 40 km ≥ stage 4) No samples contact. Till unit 4 sand and gravel bodies that are well defined by existing data. The light gray areas indicate sand sand < silt Precambrian Paleozoic main surface unit in study area; outcrops and even some from continuous cores have not been positively classified (they a Des Moines-lobe till and gravel bodies defined by fewer data points. Areas where sand and gravel deposits may be 44°30' 117Ð130 ft Diamicton, loam matrix, contact with overlying unit may be gradational between are identified as 'unnamed tills' in Table 1 and Figs. 6, 7, and 8). Geochemistry of the fine 114 to 117 ft; thin sand layers; very dark gray; extremely dense; fewer shale clasts than 39 : 35 : 26 connected to the underlying sand and gravel units (Fig. 5) are shown in dark gray; in these areas Till unit 5 Clay 20Ð30%; Cretaceous shale 20Ð30%; Present in the Marshall Till Plain; fraction of the till (Gowan, 1998) may help classification, but was not undertaken. in overlying unit. Till unit 5 Figure 5. Subsurface stream sediment associated with till units 7, 8, 9, and 10. This map shows sand = silt Precambrian ≥ Paleozoic may be missing due to erosion; Quaternary glacial sediment in the study area is thickest in the southwest and northeast water in otherwise-separate aquifers may be hydraulically connected. Areas along the Minnesota Till units the distribution of sand and gravel bodies that are at least 20 ft thick, that have upper surface a Des Moines-lobe till 1025 75 130Ð132 ft Fine sand, fines upward; dark gray; sharp upper and basal contacts. River Valley where buried aquifers may be hydraulically connected with surface waters are arious stratigraphic horizons grouped (Fig. 2). Geomorphic and subsurface data (see cross sections AÐA' and BÐB') provide Clay elevations mostly between 975 ft and 920 ft (stream sediments at higher elevations are shown in on Lake sediment some evidence for an unconformity (a gap in the geologic record) beneath till units 4, 5, shown with a hachured line. The 1,050 ft bedrock elevation contour is shown. The subsurface Till unit 6 Clay 19Ð27%; Cretaceous shale 16Ð22%; May be missing due to erosion; 40 : 38 : 22 sand and gravel deposits were identified using well-construction records. The stratigraphic context Figure 4). The medium gray areas indicate sand and gravel bodies that are well defined by the cross sand < silt Precambrian ≤ Paleozoic probably includes older phases of the 132Ð135 ft Diamicton, loam matrix; very dark gray; clasts include dolomite, granite and and 6. This unconformity is associated with the broad lowland that extends from the sections of these deposits was used to construct probable channel networks. In the region near Appleton, existing data. The light gray areas indicate sand and gravel bodies defined by fewer data points. Des Moines lobe; may correlate with shale. Till unit 5 northwest to the southeast through the region (Figs. 1 and 2). The unconformity may be Areas where stream sediments may be hydraulically connected to otherwise separate underlying units D-1 through D-3 (Patterson and Silt the result of erosion related to advances of the Des Moines lobe. Erosion surfaces are sandy subsurface stream sediment is abundant, and these aquifers are probably hydraulically others, 1995) 135Ð137 ft Cobbly gravel with coarse sand. Stream sediment sands (Fig. 3) are shown in dark gray. Areas where the buried aquifers associated with till units 7, s is present at v 35 : 37 : 28 difficult to identify from well-logs, and very few holes penetrate the deepest glacial sediment, connected to the bedrock surface. 1000 100 137Ð141 ft Diamicton, loamy matrix; very dark gray; clasts include dolomite, granite and 8, 9, and 10 may be hydraulically connected with surface waters along the Minnesota River valley soil development shale. Till unit 5 but if this hypothesis is correct, till units directly beneath the Des Moines lobe tills in the are indicated with a hachured line. The sand and gravel body with a surface elevation of 995 ft is 141Ð142 ft Fine sand; light grayish brown; sharp upper and basal contacts. lowland should correlate with more deeply buried till units in the highlands to the southwest stratigraphically linked to subsurface stream sediments associated with till units 7, 8, 9, and 10. Till unit 7 Clay 15Ð24%; Cretaceous shale 0Ð10%; Well exposed, locally stratified 120,000Ð200,000 Lake sediment and northeast. There may be some tills that are preserved in highland areas that are missing Till units The elevations given on the map are the approximate upper surfaces of the sand and gravel bodies, sand = silt Precambrian > Paleozoic may correlate with Granite Falls Till of OR 420,000Ð from the lowland areas. 142Ð149 ft Diamicton, loam matrix; dark gray; calcareous; includes limestone, shale, although this may vary along the stream course. The subsurface sand and gravel deposits were grouped Matsch (1973) 460,000 yrs B.P. We have not determined dates for any of the many advances of the Des Moines lobe in on (marine oxygen metamorphic and igneous clasts, some are distinctly striated; becomes sandier towards 41 : 38 : 21 identified using well-construction records. The stratigraphic context of these deposits was used 975 125 base, where it is a sandy loam to loamy sand with visible sand layers. Till unit 5 the upper Minnesota River basin region, but based on the continuity of the surficial deposits cross Till unit 8 Clay 18Ð25%; Cretaceous shale 0Ð15%; Not stratified; otherwise similar to Till isotope stages to construct probable channel networks. sections ≤ 6 or 12) it is possible to correlate ice margins with dated margins in nearby areas (Table 1). Organic 96°30' C 96°15 96°00' 95°45' A' 95°30' B' 95°15 sand < silt Precambrian Paleozoic unit 7; may correlate with SWRA-1 or 149Ð153 ft Coarse sand with fine pebbles; gray; includes small lignite grains; thin diamicton

SWRA-2 (Patterson and others, 1995) sea level) above (feet Elevation

Depth (feet below ground surface) ground below Depth (feet at 152 ft; fine sand layer at 153 ft. Delta or stream sediment remains (red cedar branches) present beneath the Des Moines-lobe tills are older than UMRB-2 38 : 39 : 23 UMRB-3 48,500 yrs B.P., and beyond the limits of radiocarbon dating. Evidence for previous BIG STONE Lake sediment includes soil development and organic deposits > 48,500 yrs B.P. 153Ð165 ft Diamicton, loam matrix; very dark gray; uniform and unoxidized; gravelly and nonglacial periods has been found above till unit 9 (a soil development horizon) and below °15' sandy at base. Till unit 6 SWIFT 45 CROSS SECTIONS Sand till unit 10 (wood, peat and other organic material). These nonglacial deposits may contain 165Ð175 ft Coarse sand and gravel, poorly sorted; sharp upper contact with overlying till unit

between till units 4 and 5, 4 and 6, 6 and 8, 6 and 9 as well as between till units 5 and 7. 950 150 sections, as are till units 5 and 6, till units 7 and 8, and till units 10 and 11. of faceted and striated boulder A pavement Till unit 9 Clay 10Ð21%; Trace Cretaceous shale; Superior provenance; correlates with distinct pollen and plant assemblages that would allow correlation with nonglacial deposits 6; above 167 ft it is a clast-supported gravel with a sandy matrix that grades up to a sand and The location of cross sections AÐA', BÐB', CÐC', and of the There are also an uncertain number of undifferentiated units below till sand > silt Precambrian > 80% Hawk Creek Till of Matsch (1973) 39 : 39 : 22 elsewhere in the region. (5Ð25% red) pebbly sand; below 167 ft it contains less fines in the matrix, but is still not well sorted. continuous drill core are shown on the index map. The well-log data has unit 11 that are grouped with till units 10 and 11. 420,000Ð460,000 Stream sediment CHIPPEWA mostly been projected in to the lines of cross section. The well-logs used In some cases the till units were grouped, not because they were OR 620,000Ð LAC QUI 45°00' Till unit 10 Clay 20Ð30%; Cretaceous shale 0Ð10%; Contains wood (red cedar) 660,000 yrs B.P. 175Ð184 ft Diamicton, loam matrix; very dark grayish brown; dense and firm; includes sand SELECTED BIBLIOGRAPHY PARLE too thin to show, but because it was impossible to tell them apart with the Till units sand = silt Precambrian > Paleozoic are from wells drilled within one mile of each cross-section line. Where (marine oxygen layers up to 1 inch thick; pebbly towards the base; Sharp basal and upper contacts. 41 : 34 : 25 grouped isotope stages Harris, K.L., West, S.A., Lusardi, B.A., and Tipping, R.G., 1995, Quaternary stratigraphy, UMRB-1 the vertical lines representing well-log data terminate above or below the data available. A dashed line through these grouped units indicates the 925 175 Unnamed till plate 2 of Harris, K.L., project manager, Regional hydrogeologic assessment: Quaternary A ground surface elevation on the cross sections, data is derived from a possible location of a contact based on the presence of sand layers at that on organic deposits 12 or 16) cross 184Ð193 ft Coarse sand with pebbles; variable color; better sorted near base. geology—southern Red River Valley, Minnesota Geological Survey Regional RENVILLE nearby location where the ground surface elevation varies from that on horizon. Unit 9 is thin and apparently discontinuous but is not grouped 58 : 38 : 11 sections Till unit 11 Clay 20Ð30%; Cretaceous shale 0Ð15%; Not many samples Stream sediment Hydrogeologic Assessment. 44°45' the line of cross section. For most logs it is only possible to tell sandy with any other unit because it is the only till of northeastern source. Its ≤ ≤ sand silt Precambrian Paleozoic 193Ð196 ft Very pebbly diamicton, loam to clay loam matrix; dark gray; layers of coarse sand B YELLOW MEDICINE C' 48 : 46 : 06 Patterson, C.J., Lusardi, B.A., and Knaeble, A.R., 1995, Quaternary stratigraphy, plate 2 of units from non-sandy units. The cross sections are drawn at map scale reddish brown color is occasionally noted in well logs and it is easily at 198 ft. Till unit 8 (1:200,000) with 50 times vertical exaggeration. It is not possible to distinguished in outcrop. However, it can be gray when unoxidized, and Setterholm, D.R., project manager, Regional hydrogeologic assessment: Quaternary There are an uncertain number of unnamed till units present beneath till unit 11 at some locations 196Ð200 ft Coarse, poorly sorted sandy clay loam; pebbly diamicton layer with loam matrix show units less than 20 ft thick. Some units are shown as being thicker may include both local and northwest-provenance clasts. It can be missed 900 200 43 : 50 : 07 Geology—southwestern Minnesota, Minnesota Geological Survey Regional LINCOLN LYON at 198Ð199 ft; dark grayish brown. Resedimented till?

REDWOOD than they actually are, some are grouped with others, and others are simply if special attention is not paid to pebble types. Subsurface sand and gravel Hydrogeologic Assessment. 44°30' not shown. Many units that appear on the surficial map (Plate 1) were bodies have not been assigned to till units, they are shown as separate 200Ð203 ft Sand; gray with black laminae; finely laminated; laminae include lignite (?) or Gowan, A.S., 1998, Methods of Till Analysis for Correlation and Provenance Studies in other organic material. Alluvium too thin to show on the cross sections. Units Qsh, Qsd, Qsld, Qsw, Qtld, units on the cross sections. Clayey or silty lake sediment in the subsur- Minnesota, in Patterson, C.J., and Wright, H.E., Jr., eds., Contributions to Quaternary INDEX MAP Qtbr and Qssd are shown on the cross sections as undifferentiated face is mostly too thin or too difficult to portray on the cross sections. 203Ð207 ft Coarse pebbly sand; sharp upper contact; contains well-rounded pebbles. Studies in Minnesota: Minnesota Geological Survey Report of Investigations 49, p. 159Ð Shows location of cross sections and drill core. Stream sediment 63 : 32 : 05 Quaternary surficial sediments, with their identity indicated. Sediments Lake sediment from a once-extensive lake lies stratigraphically below till EXPLANATION FOR CROSS SECTIONS 178. 875 225 of glacial Lake Benson are identified as separate units (sandy delta units 7/8, and is exposed in valleys of the Yellow Medicine River and CONTINUOUS DRILL CORE 0 20406080100 0204060 207Ð223 ft Sand; fines upwards from well-sorted coarse sand to medium-fine sand. Stream sediment Matsch, C.L., 1972, Quaternary geology of southwestern Minnesota, in Sims, P.K., and sediment; silts and clays), as are other lake sediments. Till units 1, 2, and Hawk Creek. In some places till unit 7 is stratified, indicating that the ice Surficial stream sediments Cumulative % API gamma units Morey, G.B., eds, Geology of Minnesota—A centennial volume: Minnesota 3 (numbers refer to unit designation in Table 1) are grouped on the cross depositing it advanced into a lake. Three holes drilled for this study (Figures 6, 7, and 8) 223Ð225 ft Loamy sand; dark grayish brown. Stream or lake sediment Geological Survey, p. 548-560. Sandy delta sediment of Glacial Lake Benson provide continuous, essentially undisturbed four-inch- diameter core to depths of 225 ft (UMRB-1 and UMRB-2) Silts and clays of Glacial Lake Benson and 205 ft (UMRB-3). The core provides the most detailed and reliable source of information available on subsurface Figure 8. UMRB-3 (NE1/4 SE1/4 sec. 8, T. 121 N., R. 40 W., Swift County) Antelope Glacial Lake Benson Glacial Lake Benson Delta Glacial Lake Benson Glacial Lake Benson Delta A A' Till unit. Numbers indicate stratigraphic unit(s). stratigraphy. Figures 6, 7, and 8 show the elevation above Coarse Sand Grain Counts 1300 Ice Margin 1300 7/8 Some till units are grouped. sea level and the depth below ground surface for each core. Matrix Texture Gamma Log Lithologic Description and Interpretation Precambrian:Paleozoic:Cretaceous UMRB-1 Big Stone Moraine 1200 1200 Subsurface sand and gravel units Matrix texture of the glacial sediment and other non-glacial 4 Qsd and Qsld sediments is presented here as cumulative percentages of 0 0Ð4 ft Artificial fill 5/6 Qsd 1100 sand, silt and clay for each interval sampled. Gravel 1025 4Ð5 ft Fine sand; gray and yellow brown. Eolian sand or lake sediment 1100 4 Minnesota Lake sediment, clayey silt and very fine sand 1/2/3 4 River percentages are not given. Natural gamma logs are useful No samples 5Ð10 ft Organic-rich black sand grading down to dark gray sand then very fine sand (olive 7/8 4 1000 5/6 Qsw 4 1000 Bedrock, undifferentiated for distinguishing sandy units (which plot to the left) from gray) with silt; slightly calcareous; sulfur smell. Buried soil on delta sediment 5/6 Qsh 10/11 7/8 5/6 5/6 more clayey units (which plot to the right). The core 7/8 7/8 7/8 10Ð22 ft Fine sand; black to dark gray; grades down to dark gray fine to medium sand; color 900 900 Drill hole 10/11 descriptions are summaries of the stratigraphic units 25 change parallels grain-size change; calcareous; contains scattered pebbles. Delta

Elevation in Feet Elevation Elevation in Feet Elevation 10/11 identified. A geologist monitored the drilling and logged sediment 800 10/11 800 Possible contact between till units 1000 the core on site. The core was then sampled and described 22Ð33 ft Diamicton, clay loam to sandy loam matrix; dark gray; very soft; contains abundant 700 700 in greater detail in the laboratory. The interpretation of the carbonate clasts and very few shale clasts. Till unit 7 SCALE 1:200 000 stratigraphic units is shown in italics, and a summary of the 33Ð35 ft Coarse sand with pebbles, fining up to fine sand; sharp upper contact; fine silty 0 5 10 mi 62 : 29 : 09 600 600 inferred stratigraphic sequence is shown in Table 1. The sand near base. Delta or stream sediment Vertical exaggeration x 50 coarse sand grain (1Ð2 mm) composition was determined. 50 0 5 10 15 km 35Ð43 ft Diamicton, sandy loam matrix; dark gray to very dark gray brown; includes sand Coarse sand grains were divided on the basis of the inferred 975 at 40 ft and a gravel layer at 40.5 ft; firm below 40.5 ft. Till unit 7 Alexandria age of the rock type (Precambrian, Paleozoic and 43Ð47 ft Fine silty sand; pale gray; mostly quartz sand; contains lignite granules. Slope of Coteau des Prairies Moraine Cretaceous) and counted. The resulting counts were then B Cottonwood Till Plain Glacial Lake Benson Glacial Lake Glacial Lake Benson Glacial Lake Benson Delta B' Delta and/or lake sediment 1300 Benson Delta Complex 1300 averaged for samples within each stratigraphic unit. The Qsa 47Ð48 ft Sandy diamicton, sandy loam matrix; gray; sharp upper and lower contacts. Qssd, Qsld, Qsa relative proportions of different rock types can indicate the 79 : 19 : 02 75 Resedimented till 1200 4 1200 source and path of the depositing ice, and assist in correlation 950 48Ð65 ft Medium to coarse pebbly sand; variable color; contains lignite granules and other 4 Minnesota of units over a wider area. 1100 1100 5/6 4 Qsd River black grains as well as red grains; grades down from a fine-to-coarse pebbly sand with minor 4 Qsd 77 : 22 : 01 5/6 silt as well as granules and pebbles, to a medium-to-coarse sand with granules to a coarse 4 4 1000 Quaternary 7/8 444 4 4 Quaternary 1000 pebbly sand at base. Stream sediment undifferentiated 5/6 Qsh Qsh 5/6 9 5/6 5/6 undifferentiated 7/8 Every reasonable effort has been made to ensure the accuracy of the 65Ð90 ft Diamicton, sandy loam matrix; dark gray; calcareous throughout; includes many 7/8 7/8 900 7/8 900 factual data on which this map interpretation is based; however, the 100 sand layers between upper contact and 72 ft; includes Cretaceous pyrite and limestone 10 / 11 Minnesota Geological Survey does not warrant or guarantee that 70 : 20 : 10 10/11 clasts; high gamma signal below 83 ft probably due to blocky Cretaceous shale clasts.

Elevation in Feet Elevation 925 Elevation in Feet Elevation there are no errors. Users may wish to verify critical information; 10/11 800 800 sources include both the references listed here and information on file Resedimented till at the offices of the Minnesota Geological Survey in St. Paul. In 90Ð95 ft Diamicton, clay loam matrix with cobbles near base; dark gray; similar to overlying addition, effort has been made to ensure that the interpretation 700 700 unit (65Ð90 ft); includes speckled shale clasts; records the highest gamma signal. conforms to sound geologic and cartographic principles. No claim is 56 : 21 : 23 made that the interpretation shown is rigorously correct, however, and Unnamed till 600 600 it should not be used to guide engineering-scale decisions without sea level) above (feet Elevation 125

Depth (feet below ground surface) ground below Depth (feet 95Ð125 ft Diamicton, loam matrix texture, blocky structure at top (probably a truncated soil Vertical exaggeration x 50 site-specific verification. 900 profile); very dark gray-brown; contains dominantly Precambrian grains, some carbonate grains, and only rare Cretaceous grains; unoxidized (very dark gray-brown to very dark gray) 76 : 23 : 01 below 99 ft; sandy at 111.5 ft and 112Ð113.5 ft; very firm till below 113.5 ft; sharp basal and Big Stone Moraine Glacial Lake Benson Sand C Glacial Lake Benson Delta C' upper contacts. Unnamed till(s) 1200 1200 UMRB-2 125Ð145 ft Fine sand; variable color; contains lignite and wood grains and clay intraclasts; 1100 Qsd 1100 150 contact with overlying unit is sharp; below 129 ft it is a well sorted, fine to medium sand; at Qsh 1/2/3 Cottonwood 82 : 11 : 07 1/2/3 137.5 ft it includes a zone with lignite, wood and organic material; at 143.5 ft there is a sharp 4 Creek 4 875 4 4 4 change to very fine sand. Stream sediment 1000 4 5/6 5/6 9 1000 4 5/6 5/6 7/8 5/6 9 7/8 7/8 7/8 7/8 145Ð168 ft Medium to coarse pebbly sand, fining upwards; contains lignite, shell fragments, 900 10/11 900 10/11 red sandstone, red shale, and red siltstone in pebble and coarse-sand fraction; at 155 ft it 10/11 changes sharply to a quartz-rich upwards-fining very fine sand unit that contains red 85 : 14 : 01 800 800 175 (northeast-source) grains near the base. Stream sediment Elevation in Feet Elevation Elevation in Feet Elevation Silt 10/11 850 Clay 168Ð193 ft Diamicton, with matrix composed of alternating layers of dark reddish gray sandy 700 700 loam and dark gray clay loam; includes a possible truncated soil profile; core missing from 171.5 to 173 ft; below 173 ft it is a dark gray to grayish brown diamicton with scattered red 85 : 13 : 02 600 600 pebbles and seams of diamicton with a dark reddish gray sandy loam matrix. Vertical exaggeration x 50 Glaciotectonically layered till 200 193Ð195 ft Clay; black; grades down to bedded silt, very fine sand then clay, with wood at ©1999 by the State of Minnesota, Department of Natural 825 the base. Lake sediment Resources, and the Regents of the University of Minnesota REGIONAL HYDROGEOLOGIC ASSESSMENT 0 20406080100 10 30 50 70 195Ð205 ft Very fine sand to silt; gray; rare pebbles; homogeneous, with occasional hints The University of Minnesota is an equal opportunity Cumulative % API gamma units of bedding; includes shells and flakes of black organic material. Lake sediment educator and employer QUATERNARY GEOLOGY — UPPER MINNESOTA RIVER BASIN, MINNESOTA UNIVERSITY OF MINNESOTA STATE MAP SERIES MINNESOTA GEOLOGICAL SURVEY S-20, 3rd Edition D.L. Southwick, Director Minnesota Bedrock Geology

CORRELATION OF MAP UNITS

Stratified Rocks

Agr Upper Asm Kc Ku CRETACEOUS GEOLOGIC MAP OF MINNESOTA Cretaceous MESOZOIC Ju Jurassic JURASSIC

BEDROCK GEOLOGY Dl Upper and 49° 96° Lake of the Woods Du Dc Middle DEVONIAN ° Devonain Ku Agd 49 Agm Dw Ku Agm Omu Compiled by PHANEROZOIC Ami Upper and Oum Agd Agd Middle Ami Ordovician Amm G.B. Morey and Joyce Meints PALEOZOIC Ku ROSEAU Agr KITTSON Omu Omd Agr Ami Asm Middle Ju Om ORDOVICIAN Agd Amm Agd Ordovician 94° Third Edition Ku Agd Ku Ams LAKE OF THE WOODS Agr Lower Amm 2000 Ol Amv Ordovician Ami Agd Amv Ams Upper
u CAMBRIAN Ami Cambrian Agd Amv Agr Ams Ju Amv Ku Amm Amm Agd Agm MARSHALL mh Asm Agr Ams Agd Agd mf Ami 92° Ku Ku Agr Asm Asm Metamorphic and Igneous Rocks Agr BELTRAMI Asm ms Omu Asm KOOCHICHING Ast Agd eif ml Keweenawan Ami Ams eif  mnp Ami Upper Red Lake Agr Ams eg 90° Subvolcanic Supergroup mbu Agd Amv ml mafic intrusions Agm PENNINGTON mc Ku mg  MESOPROTEROZOIC 48° Adg Agr mbg Amm  mnr mdg mnn Ams     Agm eg mdg ma mt Amm Lower Red Lake Agd Agr mdg Ams Agd Agr mnn mnn Duluth Amv COOK  RED LAKE Agd Agd mdg Complex  mbu Agd mt mnn °  90 Amv Amm Amv mdg Agd Amv Amm mbu Early Logan   ma mg ml mnr Agd Agd Aps gabbros Intrusions Adg Ams POLK Ami LAKE Agd Aps eif Agd mnp Amm Agd mt  Sioux Ams Amm mdg es Ami Quartzite CLEAR- Ams mnn mnn Agb WATER Amm eif Agd eop PROTEROZOIC Agr Agd Aps eif Penokean egr Amv ITASCA mnp intrusive Kc mbg rocks Agr ma Agd Agd egd NORMAN Agr Ami  Ams Ami Amv Agd emt MAHNOMEN Agd Amv Kc ST LOUIS Agr mbu eg eif PALEOPROTEROZOIC Agd eif Animikie eif Agd HUBBARD  ° Group Amv Amm Amv ma 96 Amm Amv eq Agd mnn 47° BECKER Ams Little Falls 94° elf 47° Formation KITTSON ROSEAU  LAKE Agd  ma enr Agd Agd eg OF THE KOOCHICHING CLAY WOODS 92° Kc 1 mdg MARSHALL North Range Agr 90° ent Agr Agd CASS PENNINGTON Group Amv ° COOK 48 mt 48° RED LAKE LAKE Kc enm Ku 2 3 Ku  92° ° 17 90 eq Kc Amv POLK AITKIN R

E Agd CROW WING T BEL 4 Amm  A TRAMI eg Kc W HUBBARD 5           R emq esa egv egs eqd em evd edv eps edq mnr A 17

E

Aqz NORMAN L Ams Kc CARLTON C WADENA Kc ITASCA Ku AITKIN emq  egv Mille Lacs Group and rocks of the eq CASS enm BECKER ST. LOUIS Amm Aps CROW Penokean fold-and-thrust belt CLAY 92° Amv WING Ami eqd WILKIN 6 Algoman Ku Agr  em mf Agd CARLT intrusive WILKIN enr WADENA ON egv edv PINE emq evd 7 Agd rocks OTTER TAIL Agr LATE ° Aqz OTTER TAIL Ams evd 46 °  C 46 ARCHEAN  evd  E ent egr  B Saganaga ARCHEAN

eps S eps MORRISON A Aps

GRANT C DOUGLAS TODD N Ast

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 BENTO K esa N L Asm Agm Tonalite Agd E TRAVERSE L ISANTI C Adg Agb Amv Amm Ams  IL egs edq H BIG STONE 9 M IS Agr A  Amg 8 G Amv evd STE SHERBURNE O eop VENS POPE STEARNS Ams evd edq SWIFT eqd PINE ANOKA Mille Lacs  I emq H MIDDLE

Lake O Agd CHIPPEWA N Amg

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D HENNEPIN E T ARCHEAN

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RENVILLLE V  A mh R

W  A edq YELLOW MEDICINE C 0 50 100 km DAKOTA SCOTT SIBLEY Amg N ° mc L 92 TODD egd O NICOLLET C REDWOOD 12
u IN 11 Duluth Complex. ° L LYON LE SUEUR DESCRIPTION OF MAP UNITS 46 eg RICE GOODHUE WABASHA  E evd Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower

N BROWN  ° O mdg Felsic series—Granophyric granite and related felsic rocks.
46 T GRANT Aqz u S amphibolite facies—Includes fragmental volcanic rocks, mafic hypabyssal 44° E ° MESOZOIC ROCKS

IP 13 44

P MURRAY MORRISON COTTONWOOD WATONWAN BLUE EARTH WASECA STEELE DODGE OLMSTED WINONA Ku emt Ku Cretaceous rocks, undivided—Dakota, Graneros, Greenhorn, Carlile, Niobrara,  intrusions, graphitic argillite, and oxide iron-formation. elf mt Troctolitic and gabbroic cumulate rocks—Constitute at least nine named and DOUGLAS and Pierre formations and their nonmarine equivalents in northwestern, several unnamed intrusions. edv Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower ROCK 14 15 16  NOBLES JACKSON MAR egr KANABEC TIN FARIBAULT FREEBORN MOWER FILLMORE HOUSTON southwestern, and southeastern Minnesota. greenschist facies—Includes fragmental volcanic rocks, mafic hypabyssal eg °  96 94° 92° ma Anorthositic series—Plagioclase-rich gabbroic cumulates and related rocks. Ku Kc Coleraine Formation—Jasper-pebble conglomerate, sandstone, and shale of diverse intrusions, graywacke, graphitic argillite and oxide iron formation. egd Ku Amg MILLE origin on the Mesabi range of northern Minnesota, and unnamed sandstone  Amg SOURCES OF GEOLOGIC MAPPING USED TO COMPILE THIS MAP mg Early gabbros—Gabbro and related rocks in northeastern Minnesota that have eps Metagraywacke, metasiltstone and a variety of schistose rocks metamorphosed  LACS and shale of nonmarine to marine origin in east-central Minnesota. petrologic affinities to the Logan Intrusions. to the amphibolite facies. TRAVERSE eop egd DIGITAL MAPPING—Numbers refer to areas shown on map above. 11 Hobbs, H.C., project manager, 1995, Geologic atlas of Rice County, Minnesota: BENTON 1 Jirsa, M.A., Chandler, V.W., and Runkel, A.C., 1999, Bedrock geologic map of Minnesota Geological Survey County Atlas Series, Atlas C-9, Pt. A, 6 pls., scale Ju Jurassic rocks, undivided—Unnamed units of green, gray, brown, and red shale, ml Logan Intrusions—Diabase, porphyritic diabase, gabbro, and related felsic sills edq Denham Formation—Quartz arenite and siltstone, oxide iron-formation, marble, emt 1:100,000. POPE northwestern Minnesota: Minnesota Geological Survey Miscellaneous Map Series, white to tan micritic limestone and dolostone, and white, fine- to coarse- and dikes. mafic hypabyssal intrusions and fragmental volcanic rocks metamorphosed Map M-92, scale 1:200,000. 12 Setterholm, D.R., project manager, 1998, Geologic atlas of Goodhue County, grained sandstone and siltstone; unit contains nodules of chert and gypsum. Minnesota: Minnesota Geological Survey County Atlas Series, Atlas C-12, Pt. to the staurolite grade of the amphibolite facies. Amg Ku 2 Chander, V.W., Jirsa, M.A., and Morey, G.B., 1997, Mineral potential assessment elf A, 6 pls., scale 1:100,000. PALEOPROTEROZOIC ROCKS  STEARNS of northern St. Louis County, southeastern Koochiching County and northeastern PALEOZOIC ROCKS STEVENS egd  13 Bloomgren, B.A., 1993, Bedrock geology of Waseca County, Minnesota: Minnesota LATE ARCHEAN ROCKS BIG STONE elf ISANTI Itasca County, Minnesota: Minnesota Geological Survey Open-File Report 97-5, Du Devonian rocks, undivided—Limestone, dolomitic limestone, and dolostone of es Sioux Quartzite—Red quartzite of fluvial to possibly marginally marine origin.  eop Geological Survey Miscellaneous Map Series, Map M-73, 3 pls., scale 1:62,500 eop 9 pls., scale 1:62,000; final report, 26 p. the Cedar Valley and Wapsipinicon Groups. Includes quartz-pebble conglomerate, claystone (catlinite, also called Ami Post-tectonic mafic intrusions—Gabbro, peridotite, pyroxenite, and their meta- 3 Peterson, D.M., and Jirsa, M.A., compilers, 1999, Bedrock geologic map and mineral and smaller. esa  SHERBURNE pipestone), a basal (rhyolite) pebble conglomerate in Pipestone County, and morphic equivalents. Unit also includes small intrusive complexes of anortho- evd CHISAGO exploration data, western Vermilion district, St. Louis and Lake Counties, north- 14 Mossler, J.H., project manager, 1998, Geologic atlas of Mower County, Minnesota: Dl Lithograph City Formation, Coralville Formation and Hinckle and Eagle City Minnesota Geological Survey County Atlas Series, Atlas C-11, Pt. A, 6 pls., scale a basal (granite, quartz, chert, iron-formation) conglomerate in Nicollet County site, gabbroic anorthosite, and anorthositic gabbro. Generally characterized  eastern Minnesota: Minnesota Geological Survey Miscellaneous Map Series, Map Members of the Little Cedar Formation (Cedar Valley Group), undivided— Ku mc 1:100,000. on the Minnesota River. by pronounced magnetic signatures.
M-98, scale 1:48,000.  u Limestone, dolostone, and lesser amounts of shale. eop egd 4 Jirsa, M.A., Boerboom, T.J., and Morey, G.B., 1998, Bedrock geologic map of the 15 Mossler, J.H., project manager, 1995, Geologic atlas of Fillmore County, Minnesota: Agr eop Post-tectonic intrusions of the Penokean orogen—Small stocks of olivine Agd Multiphase intrusions of hornblende-pyroxene-bearing and biotite-bearing mon- SWIFT Virginia Horn, Mesabi Iron Range, St. Louis County, Minnesota: Minnesota Geologi- Minnesota Geological Survey County Atlas Series, Atlas C-8, Part A, 5 pls., scale  Dc Chickasaw Member of the Little Cedar Formation (Cedar Valley Group)—Light- egd ANOKA cal Survey Miscellaneous Map Series, Map M-85, scale 1:48,000. 1:100,000. pyroxenite in Morrison County; small plutons of hornblende-rich diorite and zonite, monzodiorite, diorite, syenite, and granodiorite—Typically postdates  gray to medium-gray shale and silty shale. egd Amg 5 Miller, J.D., Jr., and Chandler, V.W., 1999, Bedrock geologic map of the central Duluth 16 Runkel, A.C., 1996, Bedrock geology of Houston County, Minnesota: Minnesota gabbro that contain layers and lenses of nelsonite, pyroxenite, and anorthosite regional metamorphism and deformation associated with the Algoman orogen. Ku Amg Complex and the western part of the Beaver Bay Complex, Lake and St. Louis Geological Survey Open-File Report 96-4, 3 pls., scale 1:100,000; text, 13 p. Dw Bassett Member of the Little Cedar Formation (Cedar Valley Group) and Pinicon in Todd County. MEEKER 17 Morey, G.B., 1999, unpublished geologic map of the Mesabi iron range, northern Agr Syntectonic to pretectonic granitoid rocks—Granite and granodiorite of the WRIGHT Counties, Minnesota: Minnesota Geological Survey Miscellaneous Map Series, Ridge and Spillville Formations (Wapsipinicon Group)—Dolostone and shaly Minnesota: Minnesota Geological Survey file map, scale 1:100,000. egr Late-tectonic intrusions of the Penokean orogen—Includes the St. Cloud and Vermilion Granitic Complex, the Giants Range and Bemidji batholiths, as KANDIYOHI Map M-101, scale 1:100,000. dolostone. 6 Boerboom, T.J., Southwick, D.L., and Severson, M.J., 1999, Bedrock geology of the Rockville Granites and Reformatory granodiorite of east-central Minnesota, well as smaller intrusions of tonalite and monzonite of the Algoman orogen Ku Aitkin 30 x 60 minute quadrangle, east-central Minnesota: Minnesota Geological Oum Upper and Middle Ordovican rocks, undivided—Limestone and shaly limestone the Section 28 granite, the Cedar Mountain Complex, and other unnamed in northern Minnesota. Also includes the Odessa, Sacred Heart, and Fort CHIPPEWA Ku RAMSEYOm Survey Miscellaneous Map Series, Map M-99, 2 pls., scale 1:100,000. NONDIGITAL MAPPING 45° of the Maquoketa and Dubuque Formations, and limestone and dolostone of intrusions exposed along the Minnesota River Valley in southwestern Ridgely Granites exposed along the Minnesota River Valley in southwestern 7 Boerboom, T.J., Southwick, D.L., and Severson, M.J., 1999, Bedrock geology of the 45° Morey, G.B., 1996, compiler, Geologic map of Minnesota, bedrock geology: Minnesota the Galena Group in the Hollandale embayment of southeastern Minnesota. Minnesota. Minnesota. LAC QUI PARLE Amg egr HENNEPIN Mille Lacs 30 x 60 minute quadrangle, east-central Minnesota: Minnesota Geological Geological Survey State Map Series, Map S-20 digital version 2, scale 1:1,000,000 Om Survey Miscellaneous Map Series, Map M-100, 2 pls., scale 1:100,000. egd Agm Granite-rich migmatite—Granitic gneiss, paragneiss, schist, and migmatite in Omd WASH- and references therein. Omu Middle and Upper Ordovician rocks, undivided—Sandstone and shaly sandstone Syntectonic intrusions of the Penokean orogen—Includes the Pierz Granite, the INGTON 8 Meyer, G.N., project manager, 1995, Geologic atlas of Stearns County, Minnesota: of the Winnipeg Formation and limestone and dolomitic limestone of the Red Freedhem and Bradbury Creek Granodiorites, and several unnamed intrusions the Vermilion Granitic Complex and other parts of extreme northern Minne- Minnesota Geological Survey County Atlas Series, Atlas C-10, Pt. A, 7 pls., scales Every reasonable effort has been made to ensure the accuracy of the factual data on River Formation along the east edge of the Williston Basin in northwestern of granite, granodiorite, tonalite, and gabbro in east-central Minnesota. sota. Grades into granitoid rocks. 1:100,000 and 1:200,000. which this map interpretation is based; however, the Minnesota Geological Survey does MC LEOD Minnesota. 9 Jirsa, M.A., Chandler, V.C., Cleland, J.M., and Meints, J.P., 1995, Bedrock geologic not warrant or guarantee that there are no errors. Users may wish to verify critical emt Unnamed schistose, volcanic, and hypabyssal rocks of mafic composition and Ast Saganaga Tonalite of northeastern Minnesota—Emplaced more-or-less contem- CARVER map of east-central Minnesota: Minnesota Geological Survey Open-File Report information; sources include both the references listed here and information on file at the offices of the Minnesota Geological Survey in St. Paul. In addition, effort has been Om Middle Ordovician rocks, undivided—Decorah Shale; limestone of the Platteville volcanic, volcaniclastic, and intrusive rocks of felsic composition—May be poraneously with deposition of metasedimentary and metavolcanic rocks. 95-1, 2 pls., scale 1:100,000. Amv RENVILLE Ol made to ensure that the interpretation conforms to sound geologic and cartographic Formation; shaly rocks of the Glenwood Formation; and St. Peter Sandstone correlative with rocks of the Wisconsin magmatic terranes. YELLOW MEDICINE Ol Om 10 Mossler, J.H., and Tipping, R.G., compilers, 2000, Bedrock geology and structure Asm Paragneiss and schist-rich migmatite—Grades into undivided metasedimentary egr principles. No claim is made that the interpretation shown is rigorously correct, however, in the Hollandale embayment of southeastern Minnesota. Ku of the seven-county Twin Cities Metropolitan Area, Minnesota: Minnesota Geological and it should not be used to guide engineering-scale decisions without site-specific Animikie Group. rocks (unit Ams).
Survey Miscellaneous Map Series, Map M-104, scale 1:125,000. verification. u Omd Decorah Shale (Middle Ordovician)—Light-greenish-gray shale and lesser amounts eg Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks— egr ms DAKOTA Ams Metasedimentary rocks, undivided—Graywacke, slate, local units of conglomerate, of coquinoid limestone, especially in the upper half of the formation. Mapped Includes the Rove Formation in Cook County, the Virginia Formation in Agr Amg SCOTT arenite, graphitic slate, fine-grained felsic volcanogenic, and volcaniclastic as a separate unit where possible. SIBLEY St. Louis, Itasca, and Lake Counties, and the Thomson Formation in Carlton rocks, lean oxide iron-formation (shown in red) and its metamorphic equiva- County. Ol Lower Ordovician rocks, undivided—Shakopee and Oneota Formations of the lents. Includes the Knife Lake Group and the Lake Vermilion Formation in Amg egr eif Iron-formation—Includes the Gunflint Iron Formation in Cook County and LINCOLN Ku Prairie du Chien Group in the Hollandale embayment of southeastern Minne- northeastern Minnesota. sota. Unit consists dominantly of dolostone and dolomitic limestone. The the Biwabik Iron Formation and subjacent units of arenite and conglomerate egr Amm Mixed metavolcanic rocks—Mafic to felsic volcanic sequences that have variable RICE GOODHUE 92° Shakopee also contains intervals of quartz arenite, including a pronounced assigned to the Pokegama Quartzite in Itasca, St. Louis, and Lake Counties. Agr Also includes thin lenses of iron-formation (Remer Member) in the Virginia amounts of felsic volcanogenic and volcaniclastic rocks and lean iron-forma- LE SUEUR basal unit named the New Richmond Member. tion. Includes parts of the Ely Greenstone and the Soudan Iron Formation LYO N Ol Formation in Itasca County. Ol
u Upper Cambrian rocks, undivided—Jordan Sandstone; dolomitic, glauconitic, (shown in red) in northeastern Minnesota. NICOLLET eq Pokegama Quartzite—Quartz arenite, siltstone, and shale. Shown only in Crow REDWOOD 
and silty glauconitic rocks of the St. Lawrence and Franconia Formations; Amg es WABASHA u Wing County. Amv Mafic metavolcanic rocks—Dominantly basalt that contains thin sedimentary Ironton and Galesville Sandstones; sandy and shaly rocks of the Eau Claire units, including iron-formation (shown in red). Includes parts of the Ely BROWN Little Falls Formation. Formation; and the Mt. Simon Sandstone. Greenstone and the Newton Lake Formation in northeastern Minnesota. Also  Amg Omd elf Quartz-rich slate, argillite, and schist in the northwestward extent of the unit includes metabasalt exposed in the Minnesota River Valley.
u Du Om MESOPROTEROZOIC ROCKS and coarse-grained megacrystic garnet-staurolite-schist in the southeastward Agb Anorthosite, gabbroic anorthosite, and anorthositic gabbro of the Mentor mafic PIPESTONE WASECA mh Hinckley Sandstone—Buff to tan quartz arenite of lacustrine and eolian origin. extent—Unit has an uncertain stratigraphic position relative to other BLUE Oum Paleoproterozoic stratified units but is apparently younger than the Mille intrusive complex in Polk County. 44° COTTONWOOD DODGE EARTH 44° mf Fond du Lac Formation—Red to dark-brown shale, feldspathic sandstone, and Lacs and North Range Groups. Adg Gabbro, diorite, peridotite, and associated komatiitic flows of the Deer Lake WATONWAN MURRAY STEELE WINONA arkose of fluvial origin. Includes the Oldenberg Point Member, a pronounced North Range Group. sequence in Itasca County and the upper part of the Newton Lake Formation  basal unit of quartz-pebble conglomerate in the Duluth area. es enr Rabbit Lake Formation—Mudstone, graywacke, iron-rich strata, and associated in Lake and St. Louis Counties. OLMSTED ms Solor Church Formation—Dark-red to dark-brown shale, siltstone, and lithic mafic metavolcanic rocks metamorphosed to the greenschist facies. Includes Aps Paragneiss, schist, and amphibolite—Amphibolite-facies equivalent of units Amv  es es sandstone of fluvial origin in Scott and Carver Counties; metamorphosed to thin beds of carbonate-silicate iron-formation. and Ams; locally includes abundant intrusions of unit Agr.

Generally excellent zeolite facies. ent Trommald Formation—Carbonate-silicate iron-formation overlain by hematite u Aqz Felsic to intermediate volcanic and volcaniclastic rocks, mica schist, phyllite, Du to fair outcrop iron-formation and associated manganese oxide deposits. Also contains mc Chengwatana Volcanic Group—Basalt and related volcanogenic and interflow and granitoid rocks—Variably and cataclastically deformed. Unit forms aero- Om substantial quantities of volcanic and hypabyssal rocks of generally mafic Dw sedimentary rocks in east-central Minnesota. magnetic “quiet zone” and probably contains some rocks of Paleoproterozoic ROCK JACKSON Generally fair to composition. Metamorphosed to the greenschist facies. MOWER poor outcrop age.
u HOUSTON North Shore Volcanic Group. enm Mahnomen Formation—Claystone, shale, siltstone, and graywacke meta- Du mnp Schroeder-Lutsen basalts—Predominantly ophitic olivine tholeiitic basalt morphosed to the greenschist facies. Ku FARIBAULT MIDDLE ARCHEAN AND OLDER ROCKS NOBLES MARTIN Poor to no outcrop unconformably over older, normally polarized volcanic rocks. Based on FREEBORN Dc Amg Migmatitic gneiss, amphibolite, and granite—Montevideo and Morton Gneisses Dc FILLMORE its stratigraphic position and geochemical affinities, the unit may be correla- Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt. Ku Dl (3,600–3,000 m.y.) in the Minnesota River Valley, southwestern Minnesota; 96° tive with the Lake Shore traps of northern Michigan . emq Quartz arenite, siltstone, and chert-rich dolostone of the Trout Lake Formation ° 92° McGrath Gneiss (2,750 m.y.) east of Mille Lacs Lake; components of Hillman 94 mnn Normally polarized volcanic rocks, undivided—Basalt, andesitic basalt, rhyolite, in Crow Wing County. Migmatite southwest of Mille Lacs Lake; and Sartell Gneiss in Stearns County. Base modified from 1990 CENSUS TIGER/Line Files of Geology compiled 2000 and related volcanogenic interflow sedimentary rocks along and inland from esa Slate, argillite, and metasiltstone metamorphosed to the lower greenschist Inferred to include various younger rocks, including granitoid intrusions in U.S. Bureau of Census (source scale 1:100,000) and Digital GIS compilation and cartography by Joyce Meints; the North Shore of Lake Superior. Chart of the World (ESRI version). digital cartography by Philip Heywood facies—Includes lesser amounts of mafic hypabyssal intrusions, and frag- the Hillman Migmatite and pillowed basalt in poorly exposed areas of SCALE 1:1,000,000 mnr Reversely polarized volcanic rocks, undivided—Mixed tholeiitic diabasic and Lambert Conformal Conic Projection mental mafic volcanic rocks. southwestern Minnesota. 25 0 25 50 MILES porphyritic basalt, trachybasalt, and rhyolite in far northeastern Minnesota Standard parallels 33° N and 45° N. DIAGRAM SHOWING GEOLOGIC and porphyritic and diabasic basalt near Duluth. Includes units of a basal egv Graphitic schist, slate, and silicate iron-formation metamorphosed to the lower 25 0 25 50 75 KILOMETERS RELIABILITY BASED ON DENSITY quartz arenite, Puckwunge Sandstone and Nopeming Formation, in greenschist facies and related conditions—Includes substantial quantities Geologic contact—Located principally by inference or by airborne magnetic OF BEDROCK OUTCROP northeastern Minnesota and near Duluth, respectively. of mafic to intermediate igneous rocks. surveys except in the very few places where the contact is exposed. Subvolcanic mafic rocks, undivided. egs Graphitic schist, phyllite and slate interbedded on a fine scale. Inferred trace of a steeply dipping fault. mbu Beaver Bay Complex and other named and unnamed gabbroic-troctolitic Inferred trace of a thrust fault or structural discontinuity that is interpreted intrusions—Includes a number of other intrusions in a variety of dikes and eqd Quartzite at Dam Lake—Quartz arenite and sericitic quartz schist; includes to have involved thrust displacement—Teeth are on the upper plate. sills such as the Endion sill and the Pigeon River Intrusions. a substantial component of mafic volcanic rock fragments.  Iron-formation. mbg Selected granophyric and leuco-granitic phases of troctolitic-gabbroic intrusions em Metadiabase, undivided. in the Beaver Bay Complex. The University of Minnesota is an equal opportunity educator and employer ©2000 by the Board of Regents of the University of Minnesota