Prepared and Published with the Support of COUNTY ATLAS SERIES THE CHISAGO COUNTY BOARD OF COMMISSIONERS AND ATLAS C-22, PART A MINNESOTA GEOLOGICAL SURVEY the Minnesota ENVironment and NaturaL Resources Trust Fund Plate 3—Surficial Geology Harvey Thorleifson, Director as recommended by the LegisLatiVE-CitiZen Commission on Minnesota Resources KANABEC 93°7'30'' 93°00' 92°52'30'' COUNTY R. 22 W. PINE COUNTY R. 21 W. ( ( CORRELATION OF MAP UNITS Qp Qbs Qa 280 Qwg ( Qcd Qci 6 Qbc 300 1 6 6 ( 1 Hudson Qnm( Qnd Qwl Qa Qf Ql Qm Qe Qp Episode ( 2 3 Qm Qf 3 Qnm Qna Qnd 361 Qws ( ( 4 Qnt Qnt SURFICIAL GEOLOGY Qnd Qf 280 Qwl West Campus Qwg formation 280 ( Qp Qwl Qnd Michigan Wisconsin QUATERNARY Rush By Rush Lake City Qcd Qwr Subepisode Episode 1 RUSHSEBAQa New Brighton T. 37 N. NESSEL T. 37 N. Qbg Qbs Qbc formation Ql 280 5 A ( A' New Ulm Qnm Gary N. Meyer Qno Qni Qns Qnm Qna Qnt Qnd Qna Rush Formation Qni Qwl Cromwell 5 Qwg Qci Qcl Qcc Qcs Qct Qcd 260 2010 Formation Qna Qnd Qbc Qcl ( Qni River Qnm Ql Qp 260 Creek Qnm( 280 300 300 Qm CAMBRIAN and Qnt Ou Qbs 7 ORDOVICIAN Qp Qni ( Qbc Clam Falls 280 Qp Qna 280 mc MESOPROTEROZOIC Qbs Qwl St. Croix Qnm( volcanics ( 8 31 300 280 ISANTI COUNTY 36 Qbc 31 9 Qnt 30 36 31 Qbg Goose Qcd Qp Qbs Qwl 7 Qbc 61 20 feet (6 meters) of the surface. Where topography is steeply rolling or gullied, 280 DESCRIPTION OF MAP UNITS Qbs 1 Qp Qf 6 6 1 6 Cromwell Formation deposits are locally at or very near the surface. Com monly ( 280 35 Qci Lake Qbc QUATERNARY Qbs Neander Qna water-washed and overlain in places by a few feet (1 meter) of lacustrine, fluvial, Lake Qnd Eolian sand—Very fine- to medium-grained sand; more than 3 feet (1 meter) thick; or eolian sand in the vicinity of units Qns, Qno, and Qna, within areas covered by Qe Qbg ( Qbc 45°37'30'' Qp 45°37'30'' 280 windblown into low-lying dunes. glacial Lake Anoka, and within the patterned area of fluvial scouring. Qnm Qni ( Qna Mud Qcd Lacustrine deposit—Sand, loamy sand, and loam, with local organic-rich layers; includes Cromwell Formation (Meyer, 1999)—Glacial, fluvial, and lacustrine sediment of Superior Qni Qnd Lake Ql ( Qbs Qbc 300 Qwg human-made beaches. In places overlies muck or peat. The width of exposure provenance (Table 1), deposited by the Superior lobe (Fig. 3) and its meltwater. ( Qbc Qnt Qwl varies depending on the water level in the lake. Many deposits along the edges of Included in these map units are some low-lying areas where Cromwell Formation Goose ( Qna lakes and bogs are too narrow to be shown. sediment may be overlain by 3 feet (1 meter) or more of sandy to clayey, organic- ( Qbg Qp Qbg Floodplain alluvium—Sediment of modern rivers. Typically coarser-grained (sand and bearing colluvium, or by thin peat. The upper part of Cromwell Formation deposits T. 36 N. FISH LAKE Qp Qa Figure 2. Physical relief of the land surface in Chisago County. Elevation is 300 SUNRISE ( Qf Qcc T. 36 N. in Chisago County are commonly reworked (by the overriding Grantsburg sublobe or 4 Robour Qbc Creek MINNESOTA gravel) in the channels, and finer-grained (fine-grained sand and silt) on floodplains. Qna 9 Qcc WISCONSIN shown by color: red (higher surface elevation) grading to blue (lower surface Lake Horseshoe Generally coarsens with depth. Wider areas are typically topped and interbedded subsequent hydraulic action) and mantled in places too patchy to show by generally Lake Qa elevation). A false sun illumination at an elevation of 30° from the northwest Qnt Qcd with thin, organic-rich layers, and some depressions within the floodplains have less than 10 feet (3 meters) of younger deposits. Qnt Qwr (315°) provides contrast (gray shadowing) to accent details of landforms. The been filled with thick, silty to clayey sediment. Unit consists chiefly of sand along Lake sand and silt—Silt to medium-grained sand deposited in glacial Lakes Lind I Qnt Qcl map was created using the U.S. Geological Survey's Digital Elevation Model B 280 280 B' 300 Qp Qa the St. Croix and Sunrise Rivers, commonly overlain by about 5 feet (1.5 meters) of and II; interbeds and lenses of silty clay to gravelly sand, and scattered dropstones; ( 10 Fish Qnt Qcl with a 30-meter grid. Qna Qnm rhythmically layered in places. Likely includes deltaic sediment. Exposed along Lake Qbc Harris 9 sandy loam to loamy sand, with interbeds of organic-rich layers; gravelly in some Qni places. Contacts with other map units (except peat) are at the base of scarps along the valley walls of the St. Croix River and its tributaries. 280 260 260 92°52'30'' Winnipeg Qp Qcd all narrow deposits of tributary streams of the St. Croix River; those scarps are not Lake clay and silt—Rhythmically bedded clay and silt laid down mostly in glacial Lake Provenance Qcc 280 Qp R. 20 W. shown by a symbol. Lind I. Exposed in the bottoms and walls of channels formed by the downcutting Qp 260 Qnd Qnt 36 Qwg Peat and muck—Partially decomposed plant matter deposited in marshes, commonly glacial St. Croix River and its tributaries. At higher elevations, the unit is topped Riding 31 Qns 31 36 Qp Rainy 31 Qwg 36 Mountain Provenance 8 31 formed in ice-block melt-out depressions and in former meltwater channels. in places by clayey to loamy diamicton of the Automba phase. Towards the base, Provenance Qcc Qwl 92°45' 280 Qcd 240 Generally mapped only where greater than 4 feet (1.3 meters) thick. Includes fine- unit may include thin interbeds of diamicton. Locally capped with alluvium or R. 22 W. Chain 280 93°7'30'' 280 Lake Qwr grained organic matter laid down in ponded water, and marl (calcareous clay) at colluvium. 260 6 1 6 1 260Qcc Digital base modified from the Minnesota Department of 30 Qwl Qns 6 depth in places. Also includes narrow deposits of alluvium along streams, narrow Qci Ice-contact stratified deposit—Sand, gravelly sand, and cobbly gravel; deposited by Qnd R. 19 W. Transportation BaseMap data; digital base annotation by beach deposits, and small bodies of open water. In developed areas, many of these meltwater flowing at or behind (beneath) the retreating ice margin. Sediment can Sunrise 300 Qcs the Minnesota Geological Survey. Qna deposits have been buried under artificial fill; the organic sediment is commonly Rainy lobe Superior 280 Qwr be quite variable and is typically faulted and folded owing to collapse upon melting Provenance Elevation contours were derived from the U.S. Geological Qp Qbs removed prior to filling in areas where major structures are built. of supporting ice. Commonly includes interbeds of, and in places is capped by, Iron Range Survey 30-meter Digital Elevation Model (DEM) by the Mesabi Qwr Minnesota Geological Survey. Qp Qcc 9 Qm Marl—Calcareous clay deposited in ponded water; mollusk shells are common. Generally sandy to silty diamicton (mudflow sediment) and silt (lake sediment). Some deposits Universal Transverse Mercator Projection, grid zone 15 Qna greater than 3 feet (1 meter) thick; covered by 1 to 4 feet (0.3 to 1.2 meters) of contain boulders. Deposits generally stand as positive features in the landscape. Wadena lobe 280 1983 North American Datum North Brainerdlobe Mud Qf Qwl peat. Qct Supraglacial till—Chiefly sandy loam-textured, un sorted sediment (diamicton), with Lake Branch Qwl Qbg 12 Alluvial fan deposit—Slopewash and stream sediment consisting of loam to loamy fine- pebbles, cobbles, and boulders; sandy silt to cobbly gravel lenses are commonly Qwl Qcc Qwr Qf grained sand, with beds of silt loam, silty clay loam, fine-grained sand, and gravel. present, particularly in the vicinity of units Qci and Qcs. Superior lobe Qcl Qf ! ! ! NORTH BRANCH AMADOR ! T. 35 N. SUNRISE Qna T. 35 N. Lithology reflects the material upslope from which the sediment was derived. Subglacial till—Chiefly dense, sandy loam-textured, un sorted sediment (diamicton), ! Qcd ! N. ! ! Des Moines lobe ! Branch ! Qe 300 ! Contains variable amounts of disseminated organic debris. Unit was deposited at with pebbles, cobbles, and boulders; stratified lenses are uncommon in most places. ! Qnt ! Qbs ! ! Qnt River 95 ! ! ! the base of steep slopes and at the mouths of deep gullies. ! Exposed in the bottom of channels formed by the downcutting glacial St. Croix Grantsburg! Sunrise ! sublobe C' ! C Qwg ! Qwr ! ! 16 River. Commonly topped by a lag of boulders. ! Qnd River ° West Campus formation (Meyer, 1999; Meyer and Patterson, 1999)—Sand and gravelly ! ° 45 30' ! 45 30' Qcs ! ! ! Qna sand of mixed Riding Mountain and Superior provenance (Table 1). Coarsens to Till, sand, and gravel—Sandy till capped by, and/or interbedded with, sand and gravel. ! Qcl Qnd Qcs 14 15 Qcd cobbly gravel in places. Laid down during early, higher stages of the St. Croix Locally, patchy till over thick deposits of sand and gravel. May include small Qbc Almelund Qnd Pre-Wisconsinan Qna 280 280 Qci River, and preserved in terraces above the modern floodplain. The West Campus bodies of thick silt. Unit has gradational contacts with units Qct and Qci. Glacial 320 formation is mapped at four major terrace levels, described from youngest (lowest) and fluvial sediment are too intricately associated to distinguish at map scale. Qf 15 Qct to oldest (highest above the modern river). Qwg Sunrise Qna Qp St.