Prepared and Published with the Support of COUNTY ATLAS SERIES THE CASS COUNTY BOARD OF COMMISSIONERS, ATLAS C-43, PART A MINNESOTA GEOLOGICAL SURVEY Cass County Harvey Thorleifson, Director THE MINNESOTA DEPARTMENT OF NATURAL RESOURCES, the Minnesota Environment and Natural Resources Trust Fund Plate 4—Quaternary Stratigraphy as recommended by the Legislative-Citizen Commission on Minnesota Resources, AND the Minnesota Legacy Amendment's Clean Water Fund
A CSS-5 (276617) A' 1,400 bdt2 Pike Bay Middle Sucker Lake Foot Lake U.S. Highway 2 Lake Winnibigoshish Mississippi River sc sc 1,300 bds1 hti2 hta1 hsa2 hsa3 bds1 hsa2 bdt2 hta2 hta2 hsa4 hti2 1,200 hsa3 hta3 hsi2 brt1 sct sfs1 sft1 sft1 sct mlt1 mlt2 ebt1 ebt2 mlt2 QUATERNARY STRATIGRAPHY 1,100 mlt3 sft2 ebt2 ebl3 ebt2 ups1 et2 1,000 mt ml mt Amv mi By 900 ups1 Amv ups1 800 Elevation in feet above mean sea level Abd Barbara A. Lusardi, Maurice K. Nguyen, and Amie E. Staley 700 LOCATION DIAGRAM
B B' 2018 1,400 Crooked Lake Sucker Bay Leech Lake CSS-6 (276618) Leech Lake River Leech Lake River Mud Lake Mississippi River bds1 sc pgs hti1 sc sc bds1 pgs sc 1,300 hti1 bds1 bdt2 bds1 bdt1 sft1 mlt1 bdl2 hti2 hsa1 hta1 hsa1 hti2 hti2 mlt2 1,200 brt1 brs1 hsa2 hta2 hsa2 mlt3 sct hsa3 sft2 sft3 hsa3 hta3 et1 1,100 mls3 mlt3 es2 ebt2 uns1 ebs2 ebs2 ups1 et2 ups1 1,000 uns2 ups1 mt Amv Agr uns2 ups2 Amv Aif 900 Amv Aif Aif Borehole name: CSS-1; unique number: 276613 Borehole name: CSS-2; unique number: 276614 800 Avs Amv Location: T. 140 N., R. 27 W., sec. 13; DDBC Location: T. 54 N., R. 27 W., sec. 9; DCDA Elevation in feet above mean sea level CASS COUNTY (sands associated with Elevation in feet above mean sea level: 1,360 Elevation in feet above mean sea level: 1,433 700 underlying till unit) Depth Matrix texture Lithology Coarse-grained sand lithology Depth Matrix texture Lithology Coarse-grained sand lithology (feet) (feet) sc pgs 0 Approximate age before present) !Cass Lake Marine Isotope Geologic age
(calibrated years East 0 Speculated West C C' Stage (MIS) age bdo, bdl hti0 ( bdg ist0 iss1 1,600 1 (( ( " ( ( hl al, eolian -10 A ( A' bds hio Blackduck Formation hti1 -10 !Bena 13,650 CSS-5 bdt hsi Hewitt Formation, ist1 -20 ou hti2 -20 1,500 Long Lake Walker Bay Leech Lake Town Line Lake Lake Lomish Boy River Little Swift Lake bdl2 hti iso, isl Itasca phase bds, bdt Blackduck Formation ist2 iss1 iss isg Independence Formation, hta1 -30 ist1 -30 hsi1 hti1 hsi1 hsi1 hig ist3 ou bdt1 ist South Long Lake Member 1,400 hti1 hsi1 bds1 hta2 -40 sc ou, tel, teu ist4 -40 hsi2 ou isl2 hti2 hti2 bds1 hti1 sc hsa Hewitt Formation, hta3 hsi2 bds1 sc hti1 hti1 iss1 ist1 iss1 (( ((( ((( ((( ( (((( -50 -50 hta1 hsa1 sc hsi2 hsi2 iss1 ( ( ( (((!((( "( (( hta Alexandria phase ist5 1,300 hta1 ist3 2 B B' hsa2 hti2 iss3 hsi, hti Hewitt Formation, Itasca phase Federal Dam hta4 iss2 -60 hta2 ist4 ist4 CSS-6 EXPLANATION ist6 -60 hsa2 bds1 hsa2 iss4 brl Red rock brt1 hsa3 sft3 mlt3 mlt1 iss, ist 1,200 hsa3 hta3 Amv sft2 Late Wisconsinan Browerville fragments -70 ebs2 sfs3 mls3 mlt3 sft1 brs -70 Sand iss1 hsa4 hsa4 ebt2 ebt2 sft3 Post-glacial silt and clay Formation Silt Clay mlt3 ebs2 Independence Formation brt ist2 ebt2 es2 Agr ebt2 " -80 -80 1,100 sct Ag Amv Amv et2 et2 ups1 aq hsa, hta Hewitt Formation, Alexandria phase iss3 et2 es2 et2 av et2 CSS-2 -90 Agm Agr Post-glacial sand and/or gravel unnamed -90 Aif Amv ups1 27,300 uts formation ist3 1,000 mt ups1 -100 -100 Asg av Sand and/or gravel Amv >200,000 !Walker ups1 Browerville Formation (undifferentiated as to formation) scs Lake Henry Formation, -110 -110 Red rock 900 ( ( ((((((( ( (( (((((((((((((((( ( (((( ( ( ( ( (((((( ((( ( fragments C ((((((( (((((((( (((((((((( (((( ( ( ( (( ( (( ( C' sct Sauk Centre Member Elevation in feet above mean sea level brs, brt ! mlt1 -120 -120 Remer Silt and clay Lake Henry Formation, mls Lake Henry Formation, sft1 800 Sauk Centre Member -130 iss4 -130 Riding Mountain-provenance mlt Meyer Lake Member mlt2 scs, sct ist4 -140 ist1ist1 diamicton sft2 -140 700 !Longville sfs St. Francis -150 sft Formation (lower) mlt3 -150 iss5 Winnipeg-provenance diamicton isl2 mls sft3 ist5 -160 isl2 ( (( ( (( ((((( (((((((((((((((((((((((((( (((( ((((( ( ((((((((((( ((( ( (( ( (((((((( ( ( ( -160 D D' mlt Lake Henry Formation, Meyer Lake Member ( ( (( ((!(((((((( ( ( ( ( ((((((( (((( (((( (( (((((( "( ((((( (( ebl iss6 D D' Rainy-provenance diamicton Eagle Bend -170 CSS-1 ebs -170 1,500 sc Hackensack Formation Birch Lake Boss Lake Trillium Lake Pick Lake Bungey Bay Woman Lake Heffron Lake Little Boy Lake McCarthey Lake CSS-1 (276613) Thunder Lake 8 or #" ebt -180 sft2 -180 iss1 greater sfs, sft St. Francis Formation (lower) CASS-1 Superior-provenance diamicton mlt1 sc ist1 sfs3 1,400 hsi1 hti1 sc sks Shooks -190 Crystalline -190 Carbonate ist1 ist1 ou through skt Formation sft3 Sand Silt Clay hti2 hsi2 hti1 sc ist1 ebs hsa1 hti2 hti1 hti1 ist2 iss2 Eagle Bend Formation Unknown provenance -200 Carbonate -200 hta1 ist1 ist1 ou ist2 18 ebt Crystalline 1,300 hsa1 iss1 iss3 ist3 sft1 hsa2 hta2 hsa2 iss3 ou iss2 iss2 ist2 usw unnamed ist2 iss3 ist3 mls1 unnamed formation -210 -210 hsa3 hsa2 iss4 iss5 ist4 iss4 skt, sks Figure 3. Stratigraphic position of sand and gravel utw formation ebt2 hta3 hsa3 sfs2 iss4 ist4 iss5 iss4 usw, utw mlt2 brt1 sft2 mlt1 Pre- Late Wisconsinan 1,200 sct sft3 sft2 -220 -220 mlt3 sfs3 ebs2 ebt2 sft1 Shooks Formation bodies depicted in the cross sections and figures. By scs sks sfs3 mlt3 ebs2 sft3 mlt3 es es Elmdale -230 et2 Acg skt et2 Elmdale Formation convention, the name designations of sand and gravel et Formation -230 sft2 es2 sft3 es2 ebt2 et Figure 2. Location of the 135 cross 1,100 sft3 ( ( ((( (( (((( ((((((( es2 Asg (( ( ( (( (((((((((( (((!(((((( ( bodies are associated with their underlying till (unless -240 Acg Acg et2 E E' sections, constructed at regular 0.6-mile -240 et2 ac Pine River ml et2 (1-kilometer) intervals, used to create a otherwise interpreted from rotary-sonic core data). On Mulligan -250 mlt3 1,000 ups1 ups1 ms -250 av av ms, mt the cross sections, tills and associated sands of several Formation three-dimensional model of the Quaternary mt Shale -260 Acd Mulligan Formation -260 sft3 900 ups1 deposits of Cass County. Cross sections formations are subdivided into multiple layers. Units that are complex and subdivided into three or more uns undifferentiated -270 -270 uns, ups A–A' through F–F' appear on this plate. ups Pleistocene sediment 0 20 40 60 80 100 0 20 40 60 80 100 Elevation in feet above mean sea level Older tills -280 800 Squares denote the locations where rotary- layers are broken down and depicted here. These layers cumulative percent cumulative percent are identified by ascending numbers from the surface -290 20 CSS-4 sonic cores were collected. Open circles bedrock Figure 4. Cass County rotary-sonic core CSS-1. Independence 700 and " denote the location of water wells within down. Some units are divided into only two layers -300 greater ( (( ( ( ( (( (( ( Formation till has been subdivided into multiple units on the cross (((((( ( (( ( ( ( (((( ((( ( (((((((((( for processing purposes, but are depicted as one layer F F' 0.3 mile (0.5 kilometer) of the published -310 EXPLANATION " sections based on sand lenses within the core. This sequence can be E E' cross sections. here, including units bdt, brt, ebt, et, and ups. Colors 1,500 Goose Lake Clam Lake Norway Lake CSS-3 interpreted in two ways: these sands represent former water flow in -320 Riding Mountain-provenance Rainy-provenance represent provenance from which the sediments were 0 20 40 60 80 100 0 20 40 60 80 100 deposits small tunnels within the ice (such as a single event leaving behind iss1 ou deposits derived. Multiple formations from the same provenance cumulative percent cumulative percent 1,400 iss1 ist1 Winnipeg-provenance Superior-provenance till and isolated sand bodies); or the sands represent a shift in the ou CROSS-SECTION SYMBOLS deposits are distinguished by shades of the base color. Gray text hta1 hsa1 ist3 pgs sc deposits ice-margin position, which allowed meltwater to flow in front of Figure 5. Cass County rotary-sonic core CSS-2. This core was hsa2 hta2 brs1 ist4 Period of sediment erosion Deposits of unknown indicates units found in the regional stratigraphy but not 1,300 iss3 ou ist1 Geologic contact—Approximate. No-line boundaries occur where data are insufficient to the ice, depositing sand and gravel outwash. This was followed drilled just outside of the county to the east in what is interpreted brt1 sft2 iss4 ist3 iss3 iss1 and/or deposition of provenance encountered in drill holes in Cass County. Associated sfs2 sfs2 reliably extend units. nonglacial sediment by a readvance of ice from the same provenance that deposited to be an ice-marginal moraine consisting of a complex mixture ist5 sft1 1,200 sct mlt3 sft3 iss5 surficial map unit labels are shown, where appropriate, of glacial till and sand and gravel (see Plate 3, unit ). For the sfs3 Bedrock contact—Contact point shown at the base of the Quaternary deposits with the Figure 1. Diagram showing relative age, location (from west to another layer of similar till on top of the sand and the process isg sfs3 beneath the stratigraphic unit boxes and labels. et2 mlt3 Amv repeated as the ice margin shifted (multiple events leaving behind purpose of modelling, however, mixed unit isg is combined with 1,100 et2 associated bedrock map unit label from Plate 2, Bedrock Geology. east), provenance (see Plate 3, Fig. 2), and related unit labels from es2 !Pillager till unit on cross sections (not shown here; see digital GIS files) av es2 Bedrock fault—See Plate 2. the cross sections for Wisconsinan and pre-Wisconsinan glacial layers of similar tills separated by sand bodies). The sands within ist ups1 and sand models (see Plate 5). The lacustrine unit below till unit 1,000 deposits. The age column and deposit drawings are schematic and the Independence Formation till were most likely deposited by a ups1 Drill hole—The top of the drill hole may not coincide with the cross-section surface- is not associated with the underlying till unit ( ), as dictated not to scale. Multiple advances of an individual formation are not combination of both processes described above—small isolated sand ist1 mlt1 elevation line because the drill hole may be located near (commonly within 0.3 mile by convention; instead, based on textural and lithologic analyses, it 900 shown. Dashed lines indicate units found in the regional stratigraphy bodies (many too small to show on the cross sections) deposited Elevation in feet above mean sea level [0.5 kilometer]) but not on the cross-section line, and therefore may have a slightly is interpreted to be part of the overlying Independence Formation but not encountered in drill holes in Cass County. Marine Isotope LITHOLOGIC PATTERNS FOR FIGURES 4 THROUGH 10 within the main till body (single event), and larger, more widespread different surface elevation. Minnesota Geological Survey unique numbers are given Patterns may be mixed within units and is therefore labelled . At this location, two units repeat in 800 Stage (MIS) correlations were estimated using figures in Jennings and sand layers laid down in front of the ice margin as the ice shifted isl2 for rotary-sonic drill holes with stratigraphic logs provided in Figures 4 through 10. couplets up to three times. Till of the Meyer Lake Member of the others (2006). A radiocarbon date of 13,650 cal years B.P. (11,635 position (multiple events). Similarly, the till of the St. Francis Speculative area—Denotes the area below the depth of drill holes and thus where identification Sand/gravel Lake Henry Formation alternates with till of the lower St. Francis ± 350 radiocarbon years B.P.) from lake sediment of glacial Lake Formation is subdivided. In different cores, other units may also of unit boundaries and sand bodies is highly speculative. Areas correspond to those Formation. This repetition is noted in other cores as well (Figs. F Seven Lakes F' Aitkin II constrains the minimum age of the underlying till, which is be subdivided into multiple layers separated by sands. Based on 1,500 shown on Plate 5, Sand-Distribution Model. Silt/clay the stratigraphic relationships drawn from these other cores, it has 7, 8). Subtle differences in the texture and/or very coarse-grained iss1 correlative to the Blackduck Formation (Farnham and others, 1964). iss1 sand lithology (Fig. 11) allow for the identification of specific Martin Creek Tower Creek ist1 Goose Lake Gull River See Figure 2 in Meyer (2015) for a discussion of the radiocarbon been interpreted that the St. Francis, Eagle Bend, and Elmdale 1,400 Till layers of the sequence even where some layers are missing (Figs. dates and sources for the Hewitt and Browerville Formations. Formation tills sampled from this location may be from a lower iss1 hta1 ist3 iss3 sc 4, 9). Below unit , core recovery was poor and there was not 1,300 brt1 ist4 iss4 iss4 iss3 position in the sediment sequence. In most cases, there is little to sft3 ist4 iss3 iss5 ist5 iss5 iss1 iss6 Organic-rich sediment sufficient material to characterize the sediment or assign it to a mls2 iss6 ist3 no textural or lithologic distinction between numbered units of the scs ist6 ist6 mls1 iss6 particular stratigraphic unit. 1,200 sct mlt2 mlt1 iss4 same formation (Fig. 11). Laminated, non-calcareous, gray-blue Ams Amv sft1 Bedrock utw sft2 mlt2 clay starting at a depth of 248 feet (76 meters) is interpreted to be mlt3 sft2 1,100 ups1 sft3 uns1 Cretaceous bedrock (see Plate 2, Bedrock Geology). Amv av ups1 Area of no recovery 1,000 Elevation in feet above mean sea level Vertical exaggeration = 50x
Borehole name: CSS-3; unique number: 276615 Borehole name: CSS-4; unique number: 276616 Borehole name: CSS-5; unique number: 276617 Borehole name: CSS-6; unique number: 276618 Borehole name: CASS-1; unique number: 274297 INTRODUCTION therefore, units are identified by thin sand or lake layers that separate the than does the Meyer Lake Member (Fig. 11; Table 2). In Morrison County Location: T. 135 N., R. 31 W., sec. 8; AABC Location: T. 136 N., R. 30 W., sec. 22; DDDD Location: T. 145 N., R. 30 W., sec. 13; DDBC Location: T. 144 N., R. 28 W., sec. 35; DCCD Location: T. 140 N., R. 29 W., sec. 32; BDCC tills and indicate a change in depositional environment. The separate layers to the south, the two members of the Lake Henry Formation are typically Elevation in feet above mean sea level: 1,400 Elevation in feet above mean sea level: 1,313 Elevation in feet above mean sea level: 1,389 Elevation in feet above mean sea level: 1,295 Elevation in feet above mean sea level: 1,414 This Quaternary Stratigraphy plate shows the unconsolidated materials expected to are numbered 1 and 2 as encountered from top to bottom for processing separated by the uppermost red till of the St. Francis Formation (Lusardi, Depth Matrix texture Lithology Coarse-grained sand lithology Depth Matrix texture Lithology Coarse-grained sand lithology Depth Matrix texture Lithology Coarse-grained sand lithology Depth Matrix texture Lithology Coarse-grained sand lithology Depth Matrix texture Lithology Coarse-grained sand lithology be encountered between the land surface and bedrock surface in Cass County (Fig. 1). purposes, but are considered one unit. 2014); however, the upper Sauk Centre Member was only encountered in (feet) (feet) (feet) (feet) (feet) Cross sections A–A' through F–F’ are representative of 135 cross sections (Fig. 2) that 0 0 0 0 0 iss3 bds Loamy sand to gravelly sand (includes mapped units bdo, bdl, pe)—Outwash rotary-sonic core CSS-5 in the northwestern corner of the county, where bdt2 were constructed to create a three-dimensional model of the Quaternary deposits of Cass -10 -10 -10 -10 bds1 -10 and sandy lake sediment. it lies directly on top of the Meyer Lake Member (Fig. 8). Outside of County. The major sand and gravel bodies from this model are depicted on Plate 5, Sand- -20 Cass County, the Meyer Lake Member is typically underlain by a second -20 -20 -20 -20 bdt1 Loamy diamicton (includes mapped units , , )—Pebbly, unsorted; ist1 Shale Distribution Model; the full model and all the cross sections used to develop it can be bdt bdt bdg pe hsi1 red till of the St. Francis Formation, which in turn is underlain by older -30 -30 -30 -30 Shale -30 accessed through the digital files of the Minnesota Geological Survey. The Quaternary contains pockets of silt, sand, and gravel in places; generally light yellowish- hti1 bdl2 iss1 brown (2.5Y 6/4) where oxidized and dark grayish-brown (2.5Y 4/2) where sediments. In Cass County, however, the Meyer Lake Member and St. -40 -40 -40 -40 -40 geologic units (Fig. 3) shown on the cross sections were defined from interpretation of Francis Formation have multiple interfingering layers (Figs. 5, 7). Separate unoxidized; contains abundant pebbles, cobbles, and boulders. Unit may -50 -50 -50 hsa1 -50 -50 new data collected for this study and from existing data from previous investigations till layers and their associated sands are numbered 1, 2, 3 as encountered contain significant amounts of sand and gravel in places where the surface -60 ist3 -60 -60 (see Index to Previous Mapping on Plate 3, Surficial Geology for references to adjacent -60 -60 Sand Silt Clay from top to bottom. Slight texture differences in the Meyer Lake Member hta1 bdt2 mapping projects). These include rotary-sonic drill core from six drill holes completed unit is mapped as unit bdg—a complex mix of till and ice-contact sediments -70 have enabled identification of the middle unit ( ), which is finer grained -70 -70 -70 -70 (see Plate 3 for a detailed unit description). Glacial till. mlt2 Red rock by the Minnesota Geological Survey for this project (CSS-1 through 6; Figs. 4 through hsa2 -80 than the others (Table 2), even where the upper unit (mlt1) is missing. -80 fragments -80 -80 -80 9), one rotary-sonic drill hole described and sampled by the Minnesota Geological Survey Silty clay—Lake sediment sampled in rotary-sonic core CSS-6 below till unit hti2 bdl2 Red rock hta2 -90 . The surface lake sediment (unit ) is more coarse-grained (loamy Sauk Centre Member -90 ist3 -90 fragments -90 -90 but completed for another agency (CASS-1; Fig. 10), water-well drillers' logs, cuttings-set bdt1 bdl1 Red rock -100 Crystalline -100 descriptions, bridge-boring logs (Minnesota Department of Transportation, 2016), exposures, to sandy); therefore it is included with unit bds. Lake sediment. scs Sand to gravelly sand—Outwash. -100 -100 hsa3 -100 mls2 Red rock fragments fragments mlt2 -110 and auger samples (see Plate 1, Data-Base Map). Hewitt Formation (Johnson and others, 2016)—Sediment deposited by the Rainy -110 -110 -110 -110 Carbonate sct Loam diamicton—Pebbly, unsorted; light olive-brown (2.5Y 5/3) where -120 On the cross sections, drill holes are represented by vertical lines. Rotary-sonic drill sourced Itasca and Wadena ice lobes. Stratigraphic data from water-well -120 -120 iss4 -120 -120 oxidized and very dark gray (2.5Y 3/1) to dark gray (5Y 4/1) where sft2 records and rotary-sonic cores indicate that there are multiple till layers -130 holes are labelled with their borehole name and associated unique number (in parentheses). -130 -130 Sand Silt Clay -130 hta3 -130 Crystalline unoxidized. This unit was identified only in rotary-sonic drill core CSS-5 mlt1 Interpreted logs of the seven rotary-sonic cores are shown in Figures 4 through 10; their that are attributed to both the Itasca (units hti0, hti1, hti2) and Wadena (units -140 (Fig. 8) and has been extended to edge-match with adjacent counties. -140 -140 -140 -140 locations are shown on Figure 2. Water-well drillers' logs and cuttings samples collected , , , ) lobes that deposited the Hewitt Formation. Where ebt1 Carbonate hta1 hta2 hta3 hta4 sft1 -150 Glacial till. -150 -150 es1 from sites in adjacent counties near the Cass County border were used for interpretation sampled, the texture and composition of each layer is nearly identical (Fig. -150 -150 hsa4 Red rock fragments -160 Meyer Lake Member -160 iss5 -160 -160 and provided significant detailed stratigraphic control. Drill holes may start above or 11; Table 2; see also Plate 3, Table 2); therefore, units are differentiated on -160 mlt2 et1 iss2 -170 below the land surface because the data are projected onto the cross section from a distance the basis of thin sand layers and geographic position. Separate till layers mls Sand to gravelly sand—Outwash. -170 -170 -170 sft2 -170 and their associated sands are numbered 0, 1, 2 as encountered from top Sand Crystalline -180 of up to 0.3 mile (0.5 kilometer), where surface elevations could differ from those at the -180 -180 -180 -180 Loam to silt loam diamicton—Pebbly, unsorted; dark grayish-brown (2.5Y Carbonate cross-section line. Vertical exaggeration is 50x for all cross sections. to bottom. Unit hti1 is the surface till unit across much of the northern mlt -190 Silt ist5 Carbonate -190 portion of the county. Moving southward, the uppermost layers may be 4/2) to gray (5Y 5/1). Glacial till. -190 mlt3 Crystalline -190 -190 es2 The complexity of subsurface units shown on the cross sections is partly a function Shale sct -200 -200 -200 -200 et2 of the amount of data available. Where the data are scarce (Fig. 2 and Plate 1), the cross- eroded or missing, thus exposing older till layers at the surface. St. Francis Formation (lower unit; Johnson and others, 2016)—Sediment -200 ist2 -210 Sand Silt Clay -210 section units are generally portrayed (modeled) as continuous, with relatively uniform Hewitt Formation—Itasca phase—Sediment deposited by the Itasca ice deposited by Superior sourced ice. Regionally, the St. Francis Formation -210 sfs3 -210 mlt1? -210 uns1 -220 -220 Carbonate thicknesses and minimal elevation change. Where there are more data, units tend to be lobe as it formed the Itasca moraine across northern Cass and Hubbard consists of two distinct till layers and associated fluvial and lacustrine -220 -220 sft1 -220 ups1 Crystalline sft2 Counties. deposits that separate members of the Lake Henry Formation. -230 Clay iss6 -230 Sand Silt Clay discontinuous and variable in thickness and elevation over relatively short distances, which -230 -230 mlt2 -230 ups2 ist6 reflects more accurately the complexity of glacial deposits, especially those that are older, Sand to gravelly sand (includes mapped units )—Outwash. sfs Sand to gravelly sand—Outwash. -240 sft2 -240 hsi hio, pe 0 20 40 60 80 100 0 20 40 60 80 100 -240 -240 more deeply buried, and more eroded and dissected. These factors should be kept in -250 cumulative percent cumulative percent -250 -250 -250 ebt2 mind when viewing the cross sections. Diamicton units, interpreted to be glacial till, are Sandy loam to loamy sand diamicton (includes mapped units , , sft Sandy loam to loam diamicton—Pebbly, unsorted; dark grayish-brown (2.5Y hti hti hig -260 Figure 7. Cass County rotary-sonic core CSS-4. The sand unit -260 -260 extended across areas where there are little to no data but where it seems reasonable that pe)—Pebbly, unsorted; contains pockets of silt, sand, and gravel in places; 4/2) to dark brown (10YR 3/3). Glacial till. 0 20 40 60 80 100 0 20 40 60 80 100 -260 ebt1 cumulative percent cumulative percent below till unit ist3 is not associated with the underlying till unit -270 the tills are continuous. Although sand bodies are not drawn in all of these areas, sand generally oxidized light yellowish-brown (2.5Y 6/4) to olive-yellow (2.5Y -270 -270 Eagle Bend Formation (Johnson and others, 2016)—Sediment deposited by ( ), as dictated by convention; instead, based on textural and and gravel commonly occur at till boundaries and may be encountered in future drill holes 6/6); contains abundant pebbles, cobbles, and boulders. In places, unit mlt1 -280 Winnipeg sourced ice. Figure 6. Cass County rotary-sonic core CSS-3. At least 250 feet lithologic analyses, it is interpreted to be part of the overlying -280 -280 at the approximate depth of till contacts shown. may contain significant amounts of sand and gravel because unit includes (61 meters) of low-carbonate till interpreted to be Independence ebs2 -290 ebl Silty clay—Lake sediment. Independence Formation and is therefore labelled iss4. At the base -290 -290 The scarcity of deep water-well data, especially in northern Cass County where the surficial unit hig (see Plate 3). Glacial till. Formation deposited by the north–northeastern sourced Rainy lobe ebt2 -300 of this core, unit sfs3 grades from coarse-grained sand and gravel -300 -300 Quaternary sediment is more than 300 feet (91 meters) thicker than in the south (see cross Independence Formation—South Long Lake Member (Johnson and others, ebs Sand to gravelly sand—Outwash. (see Plate 3 for complete discussion of Quaternary history for this to fine-grained silt and clay. ebl3 -310 sections and Plate 6, Depth to Bedrock), makes it difficult to interpret and delineate the 2016), St. Croix phase—Sediment deposited by ice of the Rainy sourced region). -310 -310 et2 -320 extent of older till units and associated sand layers. Rotary-sonic drill cores provide data Brainerd lobe. As with the Hewitt Formation, there are multiple till Silty clay loam diamicton—Pebbly, unsorted; olive-brown (2.5Y 4/4) where -320 -320 skt ebt -330 for identifying these units; however, the extent of those units is highly uncertain only a layers associated with the Independence Formation. These units are not oxidized or black (2.5Y 2.5/1) where unoxidized, and dark greenish-gray -330 0 20 40 60 80 100 0 20 40 60 80 100 short distance beyond the immediate vicinity of the core location. Based on the established distinguished by phase and thus are simply numbered 0 through 6 as (5GY 4/1) where reduced. Glacial till. ml cumulative percent cumulative percent -340 -340 stratigraphy for the region (Fig. 1), interpretations have been made using limited information encountered from top to bottom, potentially encompassing deposits from Shooks Formation (Johnson and others, 2016)—Sediment deposited by Rainy Figure 9. Cass County rotary-sonic core CSS-6. This is one of two -350 -350 provided by isolated, deeper water-well records. Where there are no data available at depth, multiple phases of the Brainerd lobe. It is the authors' interpretation that sourced ice. Approximately 75 feet (23 meters) of this unit were encountered cores in which sediments interpreted to be part of the Blackduck -360 -360 the general, regional stratigraphy has been extended in a schematic fashion in order to the Wadena lobe (units hta1-4) and an early phase of the Brainerd lobe in a single rotary-sonic core (CASS-1; Fig. 10), which included two till Formation were sampled. These sediments are easily identified by -370 et2 illustrate the potential presence of previously recognized glacial units. (units ) were active in this region at the same time. Similarly, they -370 ist3-6 units, each underlain by a sand and gravel unit. Because this stratigraphic mt the presence of gray shale fragments derived from the northwest. -380 Units not separated by solid black contact lines and zones covered by a stippled pattern believe that the later Itasca lobe (units hti0-2) and the later phase of the layer has not been recognized in adjacent counties, units sks and skt are -380 Bedrock consists of black, dense clay that is interpreted to be Brainerd lobe (units ) were coeval. Norton (1982) mapped Hewitt -390 indicate areas where the regional interpretation is especially speculative. These areas of ist0-2 only identified on cross sections within the immediate vicinity of the core -390 Cretaceous in age (see Plate 2). mt -400 greatest uncertainty are also shown on the sand-distribution models (Plate 5). Identification Formation outwash (unit hsi) on top of Independence Formation outwash in which they were sampled. -400 (unit iss) and behind the St. Croix moraine, supporting the interpretation -410 of unit boundaries and sand bodies in these areas is highly speculative. sks Sand to gravelly sand—Outwash. of an early retreat of the Brainerd lobe. The authors have characterized -410 0 20 40 60 80 100 0 20 40 60 80 100 The surficial units that appear in the cross sections are similar, but not identical to cumulative percent cumulative percent the outwash behind the St. Croix moraine as undifferentiated and likely -420 those mapped and described on the surficial geology map (Plate 3), and therefore may skt Sandy loam diamicton—Very dark grayish-brown (2.5Y 3/2). Glacial till. a mix of the Rainy- and Brainerd-lobe materials. Although the Hewitt Figure 10. Cass County rotary-sonic core CASS-1. This is the have a different unit label. For comparison, the unit labels from Plate 3 are listed in the Unnamed formation—Sediment deposited by Winnipeg sourced ice. Units 0 20 40 60 80 100 0 20 40 60 80 100 and Independence Formation tills are not both present in any single u t w only core in which the Shooks Formation and one of two cores in unit descriptions in which they have been combined (also shown on Fig. 3). Peat (unit pe and were sampled in one core in Wadena County (Lusardi and Marshall, cumulative percent cumulative percent rotary-sonic drill core, it is likely that these units interfinger along the ice usw which the Mulligan Formation were identified. Bedrock consists on Plate 3) is too thin to show on the cross sections and is combined with the surrounding 2016, Fig. 5), but are widely portrayed in Wadena County cross sections margins. However, because the deposition order is unknown, the authors Figure 8. Cass County rotary-sonic core CSS-5. This is one of of weathered saprolite. surficial units as noted in the unit descriptions. Holocene sandy units, including alluvium below the Eagle Bend Formation. Stratigraphically, the unit below the 100% Blackduck Formation (units bdt1, bdt2) have followed Norton's assertion and assigned sediment of the Hewitt two cores in which sediments interpreted to be part of the Hewitt (unit al on Plate 3) and eolian sand (indicated by a pattern on Plate 3), are combined into Eagle Bend Formation is typically the Elmdale Formation; however, the CLAY Hewitt Formation, Itasca phase (unit hti2) Formation were sampled. Although similar in texture to till of the Formation (unit hti1) to be the younger and uppermost unit overlying the one unit (pgs) for the purpose of modeling. Subsurface units appear only on the cross amount of carbonate present in the 1-2 millimeter very coarse-grained sand Hewitt Formation, Alexandria phase (units hta1, hta3) Independence Formation, Hewitt Formation till contains fewer red Independence Formation (unit ist1) and have maintained that convention A. Independence Formation (units ist1, ist2, ist3, ist4, ist5, ist6) sections (labeled in italics). fraction (33 percent) is higher than the average (12 percent) that is found rock fragments and more carbonate (Fig. 11; Table 2). The authors throughout the entire sequence. Lake Henry Formation, Sauk Centre Member (unit sct) By convention, the name designations of depicted sand and gravel bodies are associated in the Elmdale Formation as defined in Johnson and others (2016). This Lake Henry Formation, Meyer Lake Member (units mlt1, mlt2, mlt3) interpret the 5 feet (1.5 meters) of till between the Sauk Centre isl Silty clay—Lake sediment. with their underlying till, except for those at the land surface and those that intersect the unit was not encountered in cores in Cass County. St. Francis Formation (units sft1, sft2, sft3) Member (unit sct) of the Lake Henry Formation and the St. Francis increasing percentage of silt lowermost unknown units (Fig. 3). However, sand and till units are likely an admixture usw Sand to gravelly sand—Outwash. Eagle Bend Formation (units ebt1, ebt2) Formation (unit sft1) to be the Meyer Lake Member (unit mlt1) of the iss Sand to gravelly sand (includes mapped units iso, isl, pe)—Outwash and of material from immediately above or below the named unit. For example, sand unit es clay Shooks Formation (unit skt) Lake Henry Formation, based on lithologic differences with depth. sandy lake sediment. is composed chiefly of outwash sediment laid down as the glacier depositing the Elmdale utw Loam to clay loam diamicton—Dark olive-brown (2.5Y 3/3). Glacial till. Elmdale Formation (units et1, et2) Alternatively, this interval could be interpreted to be a transition Sandy loam diamicton (includes mapped units , , )—Unsorted, with Formation (unit et) retreated. However, it may also include proglacial meltwater deposits ist ist isg pe Elmdale Formation (Johnson and others, 2016)—Very dark gray loamy till Mulligan Formation (unit mt) zone between the lower part of the Sauk Centre Member and the pebbles, cobbles, and boulders; pockets of silt, sand, and gravel in places. from the advance of ice that deposited the overlying Shooks Formation (unit skt). Where and bedded sediments of northern (Winnipeg) provenance. Average texture of silty 100% underlying St. Francis Formation till. If this were the case, then Generally oxidized to yellowish-brown (10YR 5/4). In places, unit may a particular stratigraphic unit is absent from the section, the units immediately above and the diamicton unit suggests that this may be the correlative Wirt Formation, clay SHALE unit sft1, currently interpreted to be part of the lower member of contain significant amounts of sand and gravel because unit includes surficial below that missing unit likely include eroded remnants that are not shown. Where data which by definition, is sandier than the Elmdale Formation. the St. Francis Formation (under the Meyer Lake Member), would unit (see Plate 3). For example, borehole CSS-2 (Fig. 5) consists of clay loam silty clay B. from rotary-sonic core samples indicate that an interval of sand is lithologically associated isg increasing percentage of clay loam actually belong to the upper member of the St. Francis Formation, 130 feet (40 meters) of surface sand and gravel. This core was drilled just es Sand to gravelly sand—Outwash. with the overlying unit, it is labelled to reflect that formation name (for example, on Fig. 7, increasing percentage of carbonate rocks which has been identified elsewhere in northern Minnesota (Lusardi, outside of the county in what is interpreted to be an ice-marginal moraine unit iss4 is associated with the overlying Independence Formation and not the underlying Loam diamicton—Very dark grayish-brown (2.5Y 3/2). Glacial till. loam 2014), but not in Cass County. Bedrock consists of fine- to medium- consisting of a complex mixture of glacial till and sand and gravel (see Plate et Meyer Lake Member). sandy loam grained quartz sandstone, which is interpreted to be Cretaceous in Mulligan Formation—Sediment deposited by Rainy sourced ice. silt loam Table 1 shows the correlation of units mapped in Cass County with those mapped in 3, unit isg). For the purpose of modelling, surficial unit isg is combined with age (see Plate 2). unit (not shown on Plate 4, see the digital GIS files). Glacial till. ml Silty clay—Lake sediment. loamy adjacent Hubbard (Knaeble, in press) and Wadena Counties (Lusardi and Marshall, 2016), ist sand where correlations can be made. Not all units were found in all counties. This variation Hewitt Formation (Johnson and others, 2016)—Alexandria phase— Sand to gravelly sand—Outwash. SAND SILT in stratigraphy between counties likely reflects the position of former ice margins. For Sediment deposited by the Rainy sourced Wadena ice lobe as it formed ms 100% increasing percentage of sand 100% example, the Red River lobe, which deposited outwash of the Goose River formation in the Alexandria moraine and Wadena drumlin field. 100% Loam diamicton—Pebbly; dark gray (2.5Y 4/1). Glacial till. Table 1. Correlation of stratigraphic units in Cass County with units identified in adjacent Wadena (Lusardi and Marshall, Table 2. Average values for the texture and composition of till units (listed in stratigraphic order) recognized in Cass County based on samples from rotary- Wadena County, did not enter Cass County. Alternatively, units may be absent from the Sand to gravelly sand—Outwash. mt RED hsa 2016) and Hubbard (Knaeble, in press) Counties. Provenance colors match those in Figure 1, with addition of blue lake sonic cores. Matrix texture (less than 2-millimeter grain-size fraction) is expressed as relative proportions of sand, silt, and clay in percent. The lithologic regional stratigraphy as a result of erosion. The Browerville Formation occurs in Wadena C. uns Undifferentiated Quaternary sand to gravelly sand—Identified in water-well sediment. composition of the very coarse-grained sand fraction (1-2 millimeters) is expressed in percent as relative proportions of crystalline rock, carbonate rock, and and Hubbard Counties, but is generally absent in Cass County, where it may have been hta Sandy loam to loamy sand diamicton (includes mapped units hta, pe)—Pebbly, logs; overlies unit ups. shale fragments. The crystalline fraction is further subdivided by rock type—light (granite and gneiss), dark (mafic-rich igneous and metamorphic rocks), red eroded. unsorted; contains pockets of silt, sand, and gravel in places; generally increasing percentage of shale fragments CASS WADENA HUBBARD Undifferentiated Pleistocene sediment—This unit includes all sediment (till, (rhyolite, agate, and sandstone), and clear quartz. The lithologic composition can also be divided into relative proportions of grains based on age—Precambrian, oxidized light yellowish-brown (2.5Y 6/4) to olive-yellow (2.5Y 6/6); ups increasing percentage of dark rocks sand and gravel, and lake silt and clay) below the lowermost identified till sand and sand and sand and Paleozoic, and Cretaceous (see Hobbs, 1998 for rock types included in these categories). The percentage of gray shale and limestone is the amount of these ACKNOWLEDGEMENTS abundant pebbles, cobbles, and boulders; streamlined into drumlin landforms. Formation gravel lake till gravel lake till gravel lake till units. Although some water wells extend below this boundary, the data grains identified in the Cretaceous fraction. Glacial till. MATRIX TEXTURE CLAST TYPE Rotary-sonic drilling was conducted by Idea Drilling and Cascade Drilling. Minnesota are too sparse to make meaningful correlations. Goose River gs percentage of total grains Geological Survey staff members Collin Giusti, Angela Gowan, Jennifer Horton, Alan CRYSTALLINE CARBONATE bdt counted of the 1-2 Pre-Late Wisconsinan increasing percentage of crystalline rocks Blackduck bds bdl2 bds bt Knaeble, and Marguerite Pettus provided essential support during rotary-sonic drilling. REFERENCES 100% 100% (1-2) millimeter fraction Thanks are extended to all landowners who allowed drilling on their property. Browerville Formation (Johnson and others, 2016)—Sediment deposited by New Ulm ns percentage of the less percentage of total crystalline Farnham, R.S., McAndrews, J.H., and Wright, H.E., Jr., 1964, A late-Wisconsin buried soil than 2 millimeter sand grains counted Winnipeg sourced ice. Dark gray Cretaceous limestone is a key indicator hsi hti Hewitt, Itasca phase hsi hsi hti fraction DESCRIPTION OF CROSS-SECTION UNITS of this unit (Table 2; see Lusardi and Marshall, 2016, Fig. 8). Stratigraphic near Aitkin, Minnesota, and its paleobotanical setting: American Journal of Science, (1-2) (0-2) data from rotary-sonic cores in Wadena County indicate that there are v. 262, no. 3, p. 393-412. increasing percentage of red rocks iss isl ist Independence (1-6) (1-2) (0-6) iss iso (Mapped unit labels are from Plate 3, Surficial Geology) Deposit description and geologic units multiple till layers that may be attributed to Winnipeg-provenance ice that Hobbs, H.C., 1998, Use of 1-2-millimeter sand-grain composition in Minnesota Quaternary hsa hta Clear quartz Cretaceous Shale Precambrian Paleozoic hsa number Total of samples Sand Silt Clay Gravel (percentage of total sample weight) Crystalline Carbonate Light Dark Red Gray shale (percentage of Cretaceous grains counted Hewitt, Alexandria phase hta hsa hat shown on cross sections and Plate 3 Limestone (percentage of Cretaceous grains counted Unit labels and descriptions in gray text represent units that have not been identified deposited the Browerville Formation. Where sampled, the texture and studies, in Patterson, C.J., and Wright, H.E., Jr., eds., Contributions to Quaternary (1-4) (1-3) (0-2) (0-2) Blackduck Formation composition of each layer is nearly identical; therefore, units are separated studies in Minnesota: Minnesota Geological Survey Report of Investigations RI-49, Unnamed Riding Mountain usrm utrm in any of the rotary-sonic cores in Cass County. They may appear on the printed cross Partially leached till (unit bdt) 3 53 27 20 5 76 3 21 100 76 3 21 0 92 7 1 14 sections, or they may only appear in the digital files accompanying this atlas. The units on the basis of thin sand layers that indicate a change in depositional p. 193-208. brs brt Browerville brl brs brl brt brs brt Till (unit bdt) 7 50 31 19 6 78 13 9 93 77 13 10 1 90 9 1 14 are included herein because they have been identified in adjacent Wadena and/or Hubbard environment. Separate till layers and their associated sands are numbered Jennings, C.E., Aber, J.S., Balco, G., Barendregt, R., Bierman, P.R., Rovey, W., II, Roy, (1-3) (1-3) (1-3) (1-3) Hewitt Formation, Itasca phase Counties and they may be shown on cross sections in an effort to edge-match with those 1, 2, 3 as encountered from top to bottom. This unit was not encountered M., Thorleifson, L.H., and Mason, J.A., 2006, Mid-Quaternary in North America, in LIGHT DARK Unnamed Superior uts uss uts 100% increasing percentage of light rocks 100% Partially leached till (unit hti) 1 62 27 11 8 91 9 0 0 91 9 0 0 88 12 0 19 counties. These units are shown with dashed outlines in Figure 1. in cores in Cass County. Elias, S.A., ed., Encyclopedia of Quaternary science: Oxford, England, Elsevier, p. Figure 11. A. Ternary diagram showing average matrix texture (less than 2-millimeter grain-size fraction) of till samples Lake Henry, Sauk Centre Member scs sct scs sct scs sct Till (unit hti) 4 55 32 13 5 87 13 0 13 86 13 1 13 88 11 1 17 brl Silt loam—Lake sediment. 1044-1050. from the rotary-sonic cores in Cass County using the U.S. Department of Agriculture textural classification system (see Independence Formation, South Long Lake Member HOLOCENE Johnson, M.D., Adams, R.S., Gowan, A.S., Harris, K.L., Hobbs, H.C., Jennings, C.E., Unnamed Rainy urs urt Table 2). Partially leached till (unit ist) 28 69 22 9 9 100 0 0 0 100 0 0 4 76 14 10 18 brs Sand to gravelly sand—Outwash. Knaeble, A.R., Lusardi, B.A., and Meyer, G.N., 2016, Quaternary lithostratigraphic mls mlt sc Fine-grained surface sediment (includes mapped units hl, pe)—Silt and clay Lake Henry, Meyer Lake Member (1-3) mls mlt mls mlt Till (unit ist) 92 65 24 11 9 97 3 0 0 97 3 0 1 80 13 7 19 units of Minnesota: Minnesota Geological Survey Report of Investigations RI-68, B. Ternary diagram showing average lithologic composition (crystalline, carbonate, and shale) of the very coarse-grained (1-3) of modern (Holocene) lake sediment and slackwater fluvial sediment. (1-2 millimeters) sand fraction in unleached samples from the rotary-sonic cores in Cass County (see Table 2). Hewitt Formation, Alexandria phase brt Loam diamicton—Pebbly, unsorted; very dark gray (5Y 3/1) to dark gray 262 p. Smoky Hills shs sht pgs Sandy surface sediment (post-glacial sands not part of a named formation (2.5Y 4/1) where unoxidized. Glacial till. C. Ternary diagram showing the average amount of light, or felsic grains (granite, gneiss, quartzite, and quartz), dark, Partially leached till (unit hta) 6 66 23 11 5 95 5 0 0 95 5 0 0 89 10 1 22 Knaeble, A.R., in press, Quaternary stratigraphy, pl. 4 of Lusardi, B.A., project manager, Unnamed Winnipeg uws uwt Till (unit hta) 4 78 19 3 2 84 16 0 0 84 16 0 0 86 13 1 22 listed below; includes eolian sand and mapped unit al)—Sand and gravel Unnamed formation—Sediment deposited by Superior sourced ice. Only 5 or mafic grains (basalt, graywacke, and other metamorphic rocks), and red grains (volcanic and sandstone) within the Geologic atlas of Hubbard County, Minnesota: Minnesota Geological Survey County sfs of modern streams and windblown silt and sand. crystalline category shown in Figure 11B (see Table 2). sft Lake Henry Formation, Sauk Centre Member feet (1.5 meters) of this unit were encountered in neighboring Wadena Atlas C-41, scale 1:100,000 St. Francis (lower) (1-3) (1-3) fs2 fl2 ft2 sts2 sft2 Till (unit sct) 5 42 43 15 11 58 42 0 0 58 42 0 0 80 19 1 11 County in a single rotary-sonic core (WAD-3; see Lusardi and Marshall, ebs ebt PLEISTOCENE Lusardi, B.A., 2014, Quaternary stratigraphy, pl. 4 of Lusardi, B.A., project manager, Eagle Bend (1-2) ebl (1-2) ebs ebt ebs ebt 2016, Fig. 7), which included finer-grained lacustrine sediment at the top. Geologic atlas of Morrison County, Minnesota: Minnesota Geological Survey County Lake Henry Formation, Meyer Lake Member Unnamed red Superior prs prt Till (unit mlt) 32 33 48 19 3 64 36 0 0 64 36 0 13 79 17 4 15 Late Wisconsinan This unit is similar in texture to the till of the older St. Francis Formation, Atlas C-31, pt. A, scale 1:100,000, 5 pls. but contains a higher percentage of red rock fragments (Table 2; see Lusardi Undifferentiated sediment—Sediment deposited by meltwater issuing from Lusardi, B.A., and Marshall, K.J., 2016, Quaternary stratigraphy, pl. 4 of Lusardi, B.A., Shooks sks skt St. Francis Formation (lower) and Marshall, 2016, Fig. 8). It contains a higher percentage of carbonate Till (unit sft) 33 44 39 17 7 81 19 0 3 80 20 0 16 73 16 11 19 multiple ice lobes of Riding Mountain and Rainy provenances. project manager, Geologic atlas of Wadena County, Minnesota: Minnesota Geological grains than does till of the Cromwell Formation, a younger advance of the Unnamed Winnipeg usw utw usw utw Survey County Atlas C-40, pt. A, scale 1:100,000, 5 pls. Eagle Bend Formation ou Sand to gravelly sand (glacial sands not part of a named formation listed Superior lobe (Lusardi, 2014). This unit was not encountered in cores in es et Elmdale es et Till (unit ebt) 26 17 41 42 3 43 57 0 8 43 56 1 31 92 7 1 34 below; includes mapped units tel, teu, ou)—Outwash (includes terraces Cass County and was extended into Cass County for continuity. Meyer, G.N., 2015, Quaternary stratigraphy, pl. 4 of Meyer, G.N., project manager, Geologic (1-2) (1-2) above the modern floodplain). atlas of Meeker County, Minnesota: Minnesota Geological Survey County Atlas C-35, Unnamed Rainy usr utr Shooks Formation uts Loam diamicton—Pebbly, unsorted; calcareous; light olive-brown (2.5Y 5/3) Blackduck Formation (Johnson and others, 2016)—Sediment deposited by ice pt. A, scale 1:100,000, 6 pls. Till (unit skt) 15 72 20 8 9 96 4 0 0 96 4 0 0 84 15 1 17 to dark grayish-brown (2.5Y 4/2). Glacial till. Mulligan ms ml mt of the Riding Mountain sourced Koochiching lobe (see Plate 3, Fig. 2). Minnesota Department of Transportation, 2016, Bridge boring logs: St. Paul, Minn., Elmdale Formation Lake Henry Formation (Johnson and others, 2016)—Sediment deposited by uns
Every reasonable effort has been made to ensure the accuracy of the factual data on which this map interpretation is GIS compilation by J.D. Hamilton, edited by Lori Robinson based; however, the Minnesota Geological Survey does not warrant or guarantee that there are no errors. Users may wish to verify critical 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 made to ensure that the interpretation ©2018 by the Regents of the University of Minnesota ENVIRONMENT conforms to sound geologic and cartographic principles. No claim is made that the interpretation shown is rigorously AND NATURAL RESOURCES The University of Minnesota is an equal opportunity educator and employer TRUST FUND GEOLOGIC ATLAS OF CASS COUNTY, MINNESOTA correct, however, and it should not be used to guide engineering-scale decisions without site-specific verification.