Prepared and Published with the Support of COUNTY ATLAS SERIES THE CROW WING COUNTY BOARD OF COMMISSIONERS AND ATLAS C-16, PART A MINNESOTA GEOLOGICAL SURVEY THE MINNESOTA DEPARTMENT OF NATURAL RESOURCES, DIVISION OF WATERS Plate 3—Surficial Geology Harvey Thorleifson, Director SURFICIAL GEOLOGY R. 29 W. 94°15' R. 28 W. R. 27 W. 94°00' R. 26 W. R. 25 W. CASS COUNTY Lizzie Lake 5 Jail Island pe 40 Lake Lake 435 bis 5 5 6 Goose bc pe 1 6 1 5 Allen 40 1 By bis 40 6 Wolf Lake Little Pine 1 40 1 6 bt Lake Papoose 405 pe 435 pe Lake Lake bt 390 Lake 390 bc Stewart bc 405 bt Lake pe 390 390Roosevelt KNAEBLE bc Clough bt 435 0 pe Alan R. Knaeble, Gary N. Meyer, and Howard C. Hobbs 0 pe al Lake Lake 39 405 42 bt 5 405 435 AITKIN COUNTY Squaw 40 pe Mitchell 390 bo 420 0 Lake 2004 Lake 39 Blue ml bo Kego Lake 420 bt Lake bo Anna 6 bt ml Lake 390 5 GAIL LAKE 390 bt TIMOTHY 40 pe T. 138 N. FIFTY LAKES EMILY pe LITTLE PINE bc T. 138 N. CORRELATION OF MAP UNITS pe pe 390 pe pe 405 Duck Eagle Lake MEYER bo bt Lake Ruth West Lake mc 46°45' Eolian Fluvial Glacial Lacustrine Paludal Anthropic 46°45' bt Fox Butterfield bt bc bc bis0 ml Lake 39 Lake 405 Buchite bis pe bo 0 Lows bt Lake 39 dl bo mc Lake Lake Mary al 390 pe 405 pe bis Brook ld Holocene bt Sand 390 bc pe 390 Lake 0 39 lt 31 pe pe ml bc 36 Trout Lake 390 36 ml 36 31 31 390 Lake Emily pe mc agl INDEX TO MAPPING 405 Big Trout bc 36 31 ut atw pe Pickerel 36 Grass Dahler mi mt Bass atl als QUATERNARY Lake Daggett Lake The index above shows the portions of Crow Wing 390 Lake Lake 390 Lake 0 390 bo 390 mbo Late Ox 5 County mapped by Knaeble and Meyer. The two dashed 39 375 40 Island pe mo mi mc mt ml Wisconsinan bo pe 6 Lake Lake 7.5-minute quadrangles (Gull Lake and Brainerd) were 1 6 1 390 1 Pleistocene 390 6 pe 1 6 1 bgl originally mapped by Hobbs (2001a, b) with subsequent pe mt bo bis bc bt btd bl 375 bc Little mc bt modifications by Knaeble. 390 mt ml bc 405 Pine Lake 375 mbo 375 405 390 ml pwt Pre-Late Upper Wisconsinan 375 bt Whitefish 420 pe Lower 405 bt al Lake Goodrich Lake 405 Whitefish Rush pe Island pe 390 Lake bc Lake mc Lake 5 mc 375 ROSS37 LAKE 375 ml mbo Mixed outwash—Sand, gravelly sand, and gravel; cobbly in places, especially bo mbo375 INTRODUCTION MAP SYMBOLS bo near former ice margins. May include ponded fine-grained sediment along 375 420 mt 0 The surficial geologic map shows the materials expected to be encountered at the land Geologic contact—Approximately located. 5 375 39 former ice margins. Includes loamy, poorly sorted intervals in places. 37 CROSS LAKE Dolney ml T. 137 N. pe FAIRFIELD T. 137 N. surface beneath the topsoil in Crow Wing County. The surface materials can be simplified The surface of the deposits has collapsed in places from ice-block melt- Eolian sand—Pattern indicates windblown sand as thick as 10 feet (3 meters) on top bc Lake mc 375 into three types: till (unsorted sediment [diamicton] deposited by glacial ice), sand and JENKINS Lower IDEAL bo out. Mantled in places by 3 feet (1 meter) or more of sandy loam- to of other mapped sediments. In a few places west and south of Brainerd Cross 375 Ross pe Hay Lake Roger pe gravel, and lacustrine sand (Fig. 1). Unit contact lines, descriptions, and map symbols loamy sand-textured unsorted sediments. The mantle in places may be eolian sand dunes are up to 30 feet (9 meters) thick. Sand is irregular Lake 375 Lake Lake were determined from observation and sampling of outcrops, gravel pits, and construction Bertha 375 mc 375 mudflow deposits that issued from the former ice margin, but it likely is in thickness and patchy in distribution on the uplands south of Brainerd bo Star Lak375e bc 390 Lake Velvet Mud exposures; description and sampling of 220 auger borings averaging approximately 20 mostly the result of mixing windblown silt with the underlying sand and and east of the Mississippi River (Hobbs, 2001a; Knaeble, 2001). Eolian Lake Lake feet (6 meters) deep; analysis of core from 3 Minnesota Department of Natural Resources gravel through cryoturbation, bioturbation, and colluvial processes. In sand is common in Glacial Lake Brainerd deposits (unit bgl) and less 375 375 mt 0 375 mbo 39 mt rotary-sonic drill holes (two in Crow Wing County and one in Aitkin County); bridge agl 375 bc Clear 375 Big Bird pe many places the unit consists largely of reworked sand and gravel of the common in Glacial Lake Aitkin II deposits (unit ), but it is difficult Lake boring logs; water-well driller's logs; analysis of cutting samples; correlation with soil Kimble Duck Lake mc pe Brainerd assemblage, or is thin over Brainerd assemblage deposits. Contacts to distinguish eolian from lacustrine deposits, as both are composed of Lake Lake bo 375 5 pe map units (Arneman and others, 1965; Brug and Gorton, 1994; Richardson, 1997); and with Brainerd assemblage outwash (unit bo) in places are gradational or well-sorted, very fine- to medium-grained sand; thus, the mapped extent Jenkins pe 37 375 390 Stark Upper 375 Greer Bass Upper Lake aerial photograph interpretation. is highly speculative where overlying glacial lake sand. pe 390 approximately located. Deposited mostly by meltwater issuing from the Hay Lake 37 bo Lake 36 Lake Dean 5 Eastham Lake pe ice margin, but also includes sand and gravel deposited by stagnant-ice Beach ridge—Sand, gravelly sand, and sand and gravel deposited at the former 36 31 Pine 31 375 36 DESCRIPTION OF MAP UNITS 36 31 5 Lake 36 40 Lake 31 atl meltwater flowing into the western end of Glacial Lakes Aitkin I and II. margins of Glacial Lake Aitkin and Mille Lacs Lake. Ossawinnamakee 375 mt 375 5 HOLOCENE AND LATE PLEISTOCENE Lake Adney 37 Includes deltaic sediment in proximity to Glacial Lakes Aitkin I and II or Stream-cut scarp—Marks a former fluvial channel. Where paired, scarps bound bis mbo Lake 371 bc Glacial Lake Brainerd sediment. 375 bc pe er pe dl Disturbed land—Land disturbed by iron-ore mining; primarily waste rock and stream-scoured areas. Till deposits downslope of scarps are fluvially 1 375 1 6 6 Riv the formerly overlying unconsolidated sediment, including sand, gravel, mi Ice-contact stratified materials—Sand, gravelly sand, and cobbly gravel; scoured and may be mantled by sand and gravel too thin and patchy to pe 1 6 al ml 1 6 1 pe Google 390 390 till, and peat. commonly includes interbeds of, and in places is capped by, sandy to map separately. Boundaries of terrace units and alluvium are commonly 375 Lake 390 mt 375 Nelson 420 al clayey flow till and lacustrine silt. Deposits contain boulders in places. at scarps and are not shown by a scarp symbol on the map. Ticks point pe 390 375 pe River Perry Lake pe Peat and other organic sediments—Partially decomposed plant matter deposited Pine Pine Lake atl Some sediments were deposited by meltwater in fans at the ice margin; downslope. mi Little 390 pe in marshes and swamps. Includes fine-grained organic matter deposited in bc 5 pe others were deposited beneath or surrounded by ice (eskers). Individual mt 37 T. 136 N. ponded water, marl (calcareous clay) at depth in places (Schwartz, 1959), General flow direction of a meltwater stream that deposited surficial sand and Pequot 405 bc Dean deposits may consist of reworked or thinly mantled Brainerd assemblage gravel—Arrowheads point in the direction that glacial meltwater last flowed Lakes bo 375 narrow deposits of alluvium along streams, narrow beach deposits, and Lake small bodies of open water. The unit is typically found in depressions; ice-contact deposits (unit bis). within a unit. Flow direction indicators may point in opposite directions mbo mc 375 mt 375 375 pe some deposits have been drained. Most depressions are interpreted to mc Till, sand, and gravel complex—Glacial, fluvial, and lacustrine sediment in adjacent units (see sec. 23, T. 47 N., R. 29 W.). Breezy bc pe DEAN LAKE agl mc agl too intricately associated to distinguish at map scale; commonly formed Sibley Point Horseshoe MISSION ml PERRY LAKE have formed from melting buried glacial ice along former glacial stream Kame—Conical hill composed predominantly of sand and gravel (secs. 15 and 22, Lake Lakes pe 390 pe by the melt-out of underlying stagnant ice, causing the collapse and SIBLEY bo bc mi channels and as irregularities on flat, poorly drained lake plains. T. 135 N., R. 29 W.; sec. 12, T. 134 N., R. 28 W.; sec. 26, T. 138 N., R. bo mixing of overlying sediment. Includes areas of till capped by or thinly T. 136 N. 390 al Floodplain alluvium—Mississippi River alluvium is generally less than 6 feet 26 W.). Interpreted to be a deposit within the confines of supporting ice. bl al 375 atw 375 bc er Riv (2 meters) of silt loam to loamy sand including scattered wood and shell interbedded with sand and gravel, as well as areas of thin till over thick When the ice melted, the sand and gravel remained above the surrounding Pelican ml bis Deer 1 sand and gravel.