Geologic Atlas of Sherburne County, Minnesota
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Prepared and Published with the Support of COUNTY ATLAS SERIES THE SHERBURNE COUNTY BOARD OF COMMISSIONERS, AND ATLAS C-32, PART A MINNESOTA GEOLOGICAL SURVEY Sherburne County Harvey Thorleifson, Director thE MinnESOta EnvirOnmEnt and Natural RESOurcES Trust Fund AS RECOMMENDED BY THE LEgislativE-CITIZEN COMMISSION ON MINNESOta RESOURCES Plate 3—Surficial Geology BENTON COUNTY SURFICIAL GEOLOGY 94° 7' 30" W. 93° 52' 30" W. R. 31 W. 94° W. R. 30 W. R. 29 W. R. 28 W. 93° 45' W. 93° 37' 30" W. STEARNS Brook BENTON COUNTY MILLE LACS COUNTY R. 27 W. Qno Qnt Qci Qcd R. 26 W. COUNTY 320 Qci Stony MILLE LACS COUNTY Qct 6 Qnt Qno 320 Qct Qct 1 Qct 6 Qco By 1 Qnt Qcd Qbs Mississippi 320 1 6 Qp 1 6 1 320 gd Qa Qng St. Francis Qcd Qct Princeton Qco 1 6 Ql Qp Qe Qno Qa ISANTI COUNTY QntSt. Cloud320 Qp 300 Qnt Qcd Battle Qp Qci 300Rice Qco Qp Barbara A. Lusardi and Roberta S. Adams Qct ¤10 320 Lake Qct Qbs Rum River Qno Qnt Qno River 300 * A Creek * Qnt )25 3 Qci * A' Qa * Qng * Qp Qci Qci 2013 * River 300 300 Qng Qcd St. Francis ¤169 Qno * Qbs gd * Brook Qct Qno Qa River Qp * Qtu Briggs HAVEN PALMER * T. 35 N. SANTIAGO BLUE HILL Qp * BALDWIN T. 35 N. Elk Qno Ql Qp 300 * * Qci Creek * Long Pond Qa Qe Qnc River Rice Qa Julia * 45° 30' N. * Lake Qe 25 * * Qp Briggs * Qp 300 Snake 300 Qci Qnt 45° 30' N Qtl 300Lake Qno CORRELATIONA OF MAP UNITS Rush B 300 Cantlin B' * Elk R. 31 W. Lake Lake * Qbs Sandy * Rice * 31 * Holocene Lake 300 Qa Ql Qp Qe 300 300 * Lake Ql River Ql Diann Qnt Lake 36 * 94° 7' 30" W. 31 300 36 31 300 36 31 Lake Qe Qtl Qtu Durgin Bergerson * 36 Pickerel 31 36 Slough Slough* Elk 300 Long 300 Lake * Qtu Lake Lake Qp Johnson 5 300 * QUATERNARY Qp 1 1 6 Slough 300Ql New Brighton 6 1 300 * 6 Pleistocene Stickney Qno 6 300 * 1 Qbs Qbg 300 * Formation 300 Qci 1 Lake * * 300 Qp Lake* Qe * New Ulm Lake * Qno Qng Qnl Qnc Qnt 300 320 * Formation C Qa Josephine 300 320 C' Qp Qe Qnt 300 Qe Fremont * 300 Clear Big Mud Cromwell 300 Lake * Qco Qci Qct Qcd Clear Lake Qtu Formation Lake 300 300 Qbs 300 300 Qco Camp 300 PRECAMBRIAN Lake gd 300 300 Qe )24 300 Orrock 300 Qci Qnt Qnl T. 34 N. Mosford 300 300 Qp 300 Lake Zimmerman 320 Jones ¤169Qnt * Qtu Qci BECKER ORROCK Qe * R. 30 W. Lake 320 Qe LIVONIA Ql Lake West * Qp Qno Qe STEARNS 300 Ann Qnc Hunter 25 Qnt * 300 ¤10 ) 300 Lake T. 34 N. COUNTY Crescent Qe 300 * 300 300 300 Lake Qnt Qct ISANTI CLEAR LAKE 300 Qci Tibbits Digital base modified from the Minnesota Department of WRIGHT COUNTY 300 * Transportation BaseMap data; digital base annotation by COUNTY Brook Qbs * the Minnesota Geological Survey. 25 D 30 Qe D' Qa 300 ANOKA Elevation contours were derived from the U.S. Geological Qci Survey 30-meter Digital Elevation Model (DEM) by the Qnt COUNTY Minnesota Geological Survey. Qnt Snake 320 Qe Universal Transverse Mercator Projection, grid zone 15 94° W. Qp MAP SYMBOLS Eagle River 32 34 Qa Qnl * 300 1983 North American Datum 36 31 Qtu 36 36 31 * Geologic contact—Approximately located. 31 St. Francis 36 GIS compilation by R.S. Lively * Qbs Becker River Qnt * Drumlin—A streamlined hill or ridge composed typically of glacial till; in places may include sand and gravel. Qtl Qtl * Lake Edited by Lori Robinson 300 * Feature formed at the base of moving ice; commonly composed of subglacial sediment. Drumlins may 4 Elk River 300 R. 29 W. * Qbs Birch be partially covered by superglacial sediment and in places are partially or totally buried by subsequent 280 Ql 1 6 3 1 ¤10 6 1 Qp glacial and fluvial deposits. Oriented in the inferred ice flow direction. Arrow shows the inferred direction 45° 22' 30" N. Lake 6 1 ( ) of ice movement; the length of the arrow is approximately equivalent to drumlin length. Drumlins in ( Qno ) Qnc 45° 22' 30" N. )25 ( Hidden ) Mississippi Qnt 300 Sherburne County were formed at the base of the Superior lobe ice. Where mapped over unit Qnt, the ( Lake Qp Qnl ) * 280 Brook * ( * ) ** 300 * * * *E' Superior lobe drumlins are mantled by till of the Des Moines lobe (New Ulm Formation). E * * ( ) * * ( * ) * Elongate ridge—Sinuous ridge of sand and gravel deposited in an ice-walled channel. The subglacial fluvial River * )( Qnc Qnt Qp * 280 sediment may be covered by 10 feet (3 meters) or more of till. Interpreted to be an esker, although no ( Thompson * ) )( 280 * Qa Qbg Qtu Lake BIG LAKE * flow direction is inferred. * * * ( * Qnt ) * * Qci * ELK RIVER * * Wood* Tibbits )( 280 Qci )( Esker—Sinuous ridge of sand and gravel deposited in an ice-walled channel. The subglacial fluvial sediment ( Qnc ) * * Lake Lake * Qbs 300 ) ( * * Mitchell Elk 300 Qnt may be covered by 10 feet (3 meters) or more of till. Arrows indicate inferred flow direction. South- ( * ¤169) ( T. 33 N. Ql * Qno Qnl ) ( 19 Qtl * * Qe )( ) Brook and west-flowing eskers are interpreted to be of Superior lobe origin and are buried by a thin drape of ( * River ) ( Big Qtu ) T. 33 N. Qa Qe )( )( Qbg ( 93° 52' 30" W. Lake Big Lake * ) Des Moines lobe deposits. Esker ridge may no longer exist due to mining of sand and gravel deposits. ) ( ( 10Qp Qci * ) ( ¤ ) 320 Esker position is inferred from the presence of narrow, elongate lakes and from aerial photographs taken ( ) Qnc ) ( ( ) ( ) ( ( Qnt ) ( Qno ) prior to excavation. ) ( ( ) Qbs ( ) 300 Qp General flow direction of glacial streams—Arrow points downstream in the direction glacial meltwater )25 Trott flowed. F Qtl Qtu F' )( )( 280 )( )( Ice margin—Ticks on up-ice side; dashed where obscure. Qtu * R. 28 W. 34 Irregular trough—Hachures point downslope; may be occupied by aligned depressions and lakes. Indicates Qa Orono Qbg that the ice surface collapsed over an ice cavern, called a tunnel valley. 36 31 * Qtu Elk River * Stream-cut scarp—Hachures point down scarp; dashed where discontinuous or obscure. Marks the bank of 36 31 Lake * 36 Qtu Qtl a former fluvial channel. Boundaries of terrace units and alluvium are commonly at scarps, so are not Qtl 1 6 Qtl Qtl shown by a scarp symbol. Where paired, scarps bound stream-scoured areas. 1 6 R. 27 W. Qa 280 280Qnc 93° 45' W. 93° 37' 30" W. R. 26 W. 1 SCALE 1:100 000 Qp 1 0 1 2 3 4 5 MILES T. 32 N. 1 0 1 2 3 4 5 6 7 8 KILOMETERS G G' coNToUR INTERvAL 20 METERS T. 32 N. Qtu ¤10 Mississippi LocATIoN DIAGRAM Qtl Qtu River 25 45° 15' N. 260 45° 15' N. ANOKA WRIGHT COUNTY HENNEPIN COUNTY COUNTY INTRODUCTION New Ulm Formation—Twin Cities Member (Johnson and others, in press)—Sediment associated with the Grantsburg sublobe of the northwest-source Des Moines This map emphasizes the distribution and origin of surficial materials in Sherburne County. lobe. Landform distribution and sediment texture were initially based on interpretation of early spring Silt to fine-grained sand—Minor interbeds of medium-grained sand; discontinuous stereo-pair aerial photographs taken in 1977 and 1978 (1:80,000). The interpretations were Qng and patchy. Deposited in the shallow water of glacial Lake Grantsburg. Fine- drawn on 1:24,000 U.S. Geological Survey topographic maps that were overlain on a 30-meter grained sediment adjacent to outwash (unit ) may include slackwater sediments digital elevation model that covered the area (Fig. 1). These interpretations were compared Qno of meltwater streams that deposited the outwash following the draining of the to a soil map for Sherburne County (Natural Resources Conservation Service, 2010), National glacial lake. Glacial lake sediment. Wetlands Inventory maps (U.S. Fish and Wildlife Service, 2010), and to well logs included in the Minnesota Geological Survey County Well Index. Fieldwork to verify and augment these Qno Sand, gravelly sand, and cobble gravel—Moderately to poorly sorted; cross- interpretations was conducted from 2010 to 2012. Most exposures consisted of excavations, bedded to flat-bedded; may be interbedded in places with unsorted sediments including construction sites and road cuts. Surface samples were supplemented with auger borings (till, cobbles, or boulders) where adjacent to glacial till. Deposits are of variable drilled to a depth of about 11 feet (3.4 meters). Additional data from previous mapping (see thickness, generally 10 to 45 feet (3 to 14 meters). Contains sediment from both Index to Previous Mapping) were included in the analyses and interpretation of map units. northeast and northwest sources including abundant crystalline rocks (basalt and Winnipeg granite), few red sandstones, many carbonate rocks, and some gray, siliceous Provenance GLACIAL HISTORY shale fragments. Outwash. St. Cloud Much of the surficial sediment across Sherburne County is sand and gravel (Fig. 2) Qnl Very fine- to medium-grained sand—Variable thickness 40 to 70 feet (12 to 21 Riding Rainy deposited during the final stages of glacial retreat. Initially, ice from the northeast crossed this Mountain Provenance meters). Interpreted to have been deposited in a lake walled by stagnant ice. As Provenance area (Figs. 3, 4). Superior lobe deposits of the Cromwell Formation (Johnson and others, in the ice melted, the lake sediment remained as a high plateau on the landscape; press) can be seen scattered across the county and are widespread below much of the surficial collapsed in places where the lake formed on top of ice.