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 SUR VEY THE MINNESOTA DEPARTMENT OF NATURAL RESOURCES, DIVISION OF WATERS Plate 6—Mineral Endowment Harvey Thorleifson, Director MINERAL ENDOWMENT R. 29 W. 94°15' R. 28 W. 94°00' R. 26 W. R. 25 W. CASS COUNTY Lizzie R. 27 W. Lake Jail Island 405 Lake Lake 435 5 5 Allen 405 6 Goose 1 Y 40 1 6 Wolf 1 By 6 40 Lake Little Pine 1 Lake Papoose 1405 435 Lake 6 Lake 390 Lake 390 Stewart 405 Lake 390 390Roosevelt Clough 435 Gary N. Meyer and Terrence J. Boerboom Lake 0 Lake 390 42 405

5 405

435 AITKIN COUNT Mitchell 390 Squaw 40 420 0 Lake 2004 Lake 39 Blue Kego Lake 420 Lake Anna 6 Lake 390 EMILY DISTRICT 390 INTRODUCTION GAIL LAKE TIMOTHY 405 R. 29 W. 94°15' R. 28 W. T. 138 N. FIFTY LAKES LITTLE PINE R. 27 W. 94°00' R. 26 W. R. 25 W. CASS COUNTY EMILY T. 138 N. The terms mineral or geologic endowment and mineral resource refer to Jail Roosevelt 405 Duc390k Lake Lake Papoose Eagle Lake geologic materials that have intrinsic economic value and thus potentially could Little Pine Lizzie Lake Lake Lake Ruth Lake Stewart West be mined and marketed. The geologic endowment of a mineral commodity can Clough Lake Lake 46°45' Lake Squaw 46°45' Fox Butterfield be defi ned and quantifi ed on observable physical and compositional attributes Kego Lake Lake AITKIN COUNTY Lake 390 Lake Mitchell 405 of the deposit, such as deposit thickness and horizontal dimensions, overburden Lake Buchite Lows Blue Anna 6 Lake 390 thickness, measure of crushing strength, and particle-size distribution. A mineral Lake Lake Lake Duck 0 T. 138 N. T. 138 N. 39 Lake Mary 405 resource is a narrower subset of a geologic endowment; it is an occurrence of Lake Brook West Fox Eagle Sand 0 geologic material of economic interest in such form and quantity that reasonable Lake Lake Ruth 39 46°45' Butterfield Lake 46°45' 390 Lake Lake 390 prospects for eventual economic extraction exist. If a part of the deposit does not Lows 31 Lake Lake 390 have reasonable prospects for eventual economic extraction, it cannot be included Mary 36 Trout Lake Brook 36 390 Lake 36 31 31 Emily in a mineral resource (Resources and Reserves Committee, 1999). Factors that may Lake 405 Big Trout 36 31 Pickerel 36 Pickerel Trout Emily Grass Dahler Bass remove some portion of an endowment from consideration as a resource are zoning Big Trout Lake Lake Lake 390 Daggett Lake Lake Lake 390 Lake Lake Daggett 390 restrictions, land ownership considerations, prohibitive taxation, competing surface 0 390 Ox 39 Ox 5 Lake Dahler 375 40 Island uses, and environmental considerations, in addition to the supply–demand–price Little Lake 6 Lake Lake Pine 390 fl uctuations of the commodity marketplace. Therefore a mineral resource must Lake 390 1 6 1 1 Upper 6 1 6 1 Lower possess favorable geologic attributes and also be relatively unencumbered by Whitefish 375 Little Whitefish Goodrich Island 390 Lake Rush Lake Lake 405 Pine socioeconomic factors that would remove it from consideration as the basis of Lake Lake 375 375 Lake 405 390 a business enterprise. The authors of this plate did not take into account these Upper Dolney socioeconomic factors, and therefore the maps portray the mineral endowment of T. 137 N. Lake 375 Lower Cross Roger Ross T. 137 N. Whitefish 420 Lake Lake Lower 405 Crow Wing County, not the mineral resource. Hay Lake Goodrich Lake 405 Lake Velvet Whitefish Rush Island 390 Lake Bertha Star Lake Lake Mud Lake Lake Lake Big Bird Lake Lake Lake 375 375 Clear 375 Duck Greer 375 ROSS LAKE Lake Kimble Lake Upper Dean Jenkins Upper Lake Pine Lake Bass Lake Lake Lake 375 420 Hay Lake 0 Lake Eastham Stark 375 375 39 Adney Lake T. 137 N. CROSS LAKE Dolney Lake Lake FAIRFIELD T. 137 N. 371 er Perry Nelson 375 Google Riv JENKINS Lower Ossawinnamakee Lake Lake Lake Lake Hay Lake IDEAL Cross 375 Roger Ross Lake 375 Lake Lake Pine River Pine 375 Pequot T. 136 N. Bertha Star Lake 375 390 Little 375 Velvet Lakes Lake Mud Breezy Dean Lake Lake Lake AGGREGATE ENDOWMENT Sibley Point Horseshoe Lake Lakes 375 0 375 375 39 375 Clear T. 136 N. Deer er 375 Big Bird Riv Lake Kimble Duck Lake By Pelican Lake Lake Lake Lake Fool 375 5 375 37 Stark Lake Jenkins 375 390 6 CUYUNA Upper Greer Bass Upper Lake Gary N. Meyer i 390 Bass Hay Lake 375 Lake 36 Lake Dean Cullen Lake NORTH Eastham Lake Lakes Indian Jack Mississipp 36 Pine 31 375 Lake 36 31 31 Lake Lake 36 2004 Mission RANGE 405 31 36 Twin Ossawinnamakee 375 Lakes Lougee T. 47 N. 375 5 Island Lake Adney 37 Lake Lake Lake Lakes Rabbit 371 375 er Perch Coles Lake 375 Lake Lake Carlson 1 6 1 6 Riv 6 INTRODUCTION Lake 1 6 Google 1 1 Nisswa 3 CUYUNA 390 390 Clark 375 Lake Johnson Casey 390 The principal Quaternary mineral endowments in Crow Wing County are sand and gravel, Lake 4 SOUTH 375 Nelson Nisswa Rice Lake Garden Lake 420 390 Perry Lake Cuyuna 375 River Lake potential sources for construction aggregate. Principal uses for aggregate are in concrete for Lake Lake Lake Silver RANGE Pine Pine Lake Roy Edward Little 390 buildings, bridges, and road pavement; in road base and fi ll; in bituminous road pavement; and Lake Lake Trommald Black Agate Black 46°30' 375 T. 136 N. 46°30' Bear Lake Lake Lake Cedar lesser uses, including riprap and landscaping. Sand and gravel deposits in Crow Wing County Lake Pequot 405 T. 135 N. Bass Dean 375 210 Lake are subdivided into three categories of aggregate potential on the basis of geologic attributes 371 Lake Lake Fawn Crosby Lakes Lake 375 and physical properties of the mapped materials. Bedrock formations in the area are too Hubert Serpent 375 Gladstone Lake 375 Gull Deerwood deeply buried to be mined for aggregate. However, waste rock in iron mine dumps may be Lake Blackhoof Breezy Horseshoe DEAN LAKE Lake Sibley Point suitable for some construction applications. Spider Lake Reno Lake Lakes MISSION PERR390 Y LAKE Lake Rice Lake SIBLEY The judgement of potential deposit quality is based predominantly on reconnaissance- Lake 1 T. 46 N. Round Riverton Portage 390 Lake T. 136 N. 375 level geologic information and interpretation. This study does not identify specifi c aggregate Lak2e 375 er Olander Hamlet Riv Lake Lake Pelican resources, which are defi ned in part on economic and societal criteria and concerns. Furthermore, Deer 210 Lookout 1 North Lake 375 Lake this assessment does not mean that economic aggregate deposits exist everywhere within a 25 Lake Long Shirt 375 given map unit; rather, the materials in each map unit were created by geologic processes Lake Fool Long Lake Lake that could have produced aggregate deposits at specifi c sites within the unit as mapped. Wolf Lake Loon 375 Lake 6 6 Geologic endowment, although imprecisely measured, is fi xed, whereas economic criteria and Horseshoe Lake 375 PELICAN 375 i Lake 360 375 environmental regulations vary across time and place. Important site-specifi c factors such as T. 134 N. issipp land ownership, zoning, protected waters and wetland designations, environmental impact, Wise 375 Lake Cullen Miss required permits, distance to markets, royalties, and site access all contribute to the fi nal Eagle Bay Lake Lakes Bass 31 Indian Jack Gilbert Hoppy Lake Clearwater Lake Mud Lake Lake 375 "potential" of a specifi c parcel. These factors are outside the scope of this study. Lake Lake 375 375 Mission Lake 36 36 31 Twin Lougee 375 Island Twin 375 371 Rice Mud Birch 31 Lake 36 375 T. 47 N. Red Sand Lake Lake Heron Lake Lakes DESCRIPTION OF MAP UNITS Lake Lake Maple 375 Lake Nokay Lake T. 45 N. Lake Lake Island RABBIT LAKE POTENTIAL SAND AND GRAVEL SOURCES—These units typically exhibit Edna Lakes WOLFORD Lake 375 geologic characteristics that indicate sand and gravel deposits may be Portage Partridge Turtle 6 White Brainerd Hanks Lake Lake 6 1 Rabbit 0 Sand 18 Lake Lake 1 Coles 36 present. Existing gravel pits and aggregate sources used by the Minnesota WhippleLake 360 360 18 Lake Department of Transportation within these units are identifi ed or known Lakes er Grave Perch Riv Round Lake Perch Lake Lake Lake resources. Geologic units that have the best potential for sand and gravel Baxter Lake Scott Carlson 210 Rice Lake Lake Nisswa 375 Lake include outwash and ice-contact sediments (eskers, kames, and fans); T. 133 N. Kenney 360 Cuyuna they typically contain sorted sand and gravel with little silt and clay. The Lake 37 Nisswa Clark Johnson 375 5 Lake Lake Lake map units are classifi ed by the thickness of sand and gravel, thickness of Roy Garden 375 Casey Miller Lake Turner Lake Upper South Lake Borden Lake 31 Lake overlying deposits, percentage of material retained on the number 4 sieve Russell Long Lake Lake Rice Lake Black 390 25 Lake 36 31 (4.76-millimeter pore space), depth to the water table, and percentage of 18 Lake Edward Silver Bear 375 36 405 36 1 Lake spall materials (Table 1). Very good to good quality deposits generally Garrison Mille Lake Lacs Trommald CASS COUNTY 371

375 375 Lake LAKE EDWARDS 360 360 contain less than 1.5 percent total spall materials. Good to moderate quality South T. 44 N. NISSWA CENTER Long 46°30' Agate 46°30' deposits generally contain less than 5 percent total spall materials. Gravel 169 375 1 Lake Lake Jack Pine 1 6 1 6 Cedar in moderate to poor quality deposits generally contain more than 5 percent 210 T. 44 N. Lake T. 135 N. 390 Black 375 Lake total spall materials. 371 Bass Crosby Lake 375 Lake Lake 360 390 Primary sand and gravel deposits—Defi ned as having a sand and gravel Smith AITKIN COUNTY Hubert 375 thickness of 20 to more than 50 feet (6 to more than 15 meters); generally Holt Fawn 375 375 46°15' Lake Lake 46°15' Lake Serpent Lake less than 5 feet (1.5 meters) of overburden; on average more than 20 percent Gladstone 375 Deerwood of material retained on the number 4 sieve; depth to water table greater than Crow Lake Ironton Wing Gull 20 feet (6 meters); and are of very good to good quality. The probability COUNTY Lake Camp

N Lake Lake River O Reno that a sand and gravel deposit exists within this unit is very high to high. Mud Round 360 Lake Lake 36 Spider Lake Nokasippi 360 Blackhoof 375 Secondary sand and gravel deposits—Have a sand and gravel thickness Lake Lake Rice Whitefish DEERWOOD ranging from near zero to more than 40 feet (12 meters); less than 10 feet MORRIS Lake 31 36 Lake Erskine Twentytwo 31 IRONDALE390 Lake Lake 390 T. 46 N. (3 meters) of overburden; generally more than 15 percent material retained Brook Round Riverton T. 43 N. T. 43 N. Lake Portage on the number 4 sieve; depth to water table greater than 10 feet (3 meters); 390 Daggett 375 Lake Olander and are of very good to moderate quality. The probability that a sand and 6 Lake Mud 1 6 390 gravel deposit exists within this unit is high to moderate. Lake Rock Bulldog Hamlet Sebie Lake Lake Lake 1 Lake Tertiary sand and gravel deposits—Consist primarily of sand and gravelly sand Platte ranging from near zero to greater than 20 feet thick (6 meters); overburden no Lake 360 210 360 more than 20 feet thick (6 meters); generally less than 15 percent material COUNTY LACS MILLE 25 375 Lookout 0 390 North 375 39 Long Lake retained on the number 4 sieve; water table from 0 to greater than 20 feet (6 R. 32 W. 94°15' R. 31 W. R. 30 W. 94°00' R. 29 W. MORRISON COUNTY R. 28 W. Lake 390 405 390 meters) below the surface, and are of very good to moderate quality. The 390 Digital base modified from the Minnesota 390 390 Shirt GIS compilation by R.S. Lively 390 Lake probability that a sand and gravel deposit exists within this unit is high to Department of Transportation BaseMap data; SCALE 1:200 000 Edited by Lori Robinson 36 moderately low. Iron mine dumps are included in this unit. digital base annotation by the Minnesota 5 0 5 10 MILES 36 31 Wolf 36 31 390 Geological Survey. 375 Lake 390 390 Long 6 Arbor 375 Lake 390 Lake LIMITED POTENTIAL FOR AGGREGATE SOURCES—The map shows Universal Transverse Mercator Projection, grid 5 0 5 10 15 KILOMETERS 375 Loon Horseshoe Goose that the remainder of Crow Wing County is underlain by geologic units zone 15 1983 North American Datum Lake 390 T. 134 N. Lake 405 Lake that have little or no potential for signifi cant aggregate resources. The units 6 1 1 6 1 may, however, include local aggregate deposits that are too small to map or Wise are unknown. BEDROCK ENDOWMENT Lake 375 Eagle IDENTIFIED AGGREGATE RESOURCES—Areas where aggregate Bay Lake By 360 Hoppy Lake 375 Lake 390 Clearwater resources have been mined or are currently being mined. Pit locations have 360 390 BAY LAKE been gathered from aerial photographs, topographic maps, the county soil Terrence J. Boerboom Mud Gilbert Lake survey (Arneman and others, 1965), and fi eldwork for this study. Lake Lake OAK LAWN NOKAY LAKE 390 Large gravel pit, or an area of more than one gravel pit or gravel-pit 2004 Twin 390 operation—The areas of larger pits shown on the map were primarily 371 390 375 375 Island determined using aerial photographs from 1992; therefore some pit areas 360 Red Sand Rice Mud Lake Heron Lake 36 31 Lake Lake Lake Nokay Birch may be more extensive than portrayed. Aggregate resources may remain INTRODUCTION rocks are comprised of metavolcanic rocks typical of Archean greenstone terranes (units Lake 390 T. 45 N. 390 Lake within some pits. Smaller pits are indicated only by the pit symbol. Inactive, Agm and Amv) that may contain iron-formation. It is known from drill core that, at least 390 The bedrock endowment map highlights bedrock units that may host mineralization 360 375 390 depleted, and reclaimed pits are shown by a line through the pit symbol. locally, the greenstone units contain hypabyssal mafi c intrusions (unit Ag). Collectively 390 or attract the interest of explorationists, and the locations of the three main districts of the these inferences imply that the greenstone belts contain a geologic complexity typical of Maple Gravel pit listed in the Aggregate Source Information System data Lake Cuyuna iron range. The map includes outlines of the bedrock geologic units from Plate 2, 1 6 other well-exposed greenstones in Ontario and northern Minnesota, and may at some point Whipple Brainerd 405 base of the Minnesota Department of Transportation—Ancillary data Bedrock Geology; see that plate for a complete description of the bedrock map units. The Lakes Partridge be examined by explorationists for indications of potential mineral deposits. Likewise, the Hanks Lake may include test-hole logs, sieve data, test data on aggregate quality, and White BAXTER Lake map also shows the locations of old mine shafts. 390 Turtle aeromagnetically inferred mafi c intrusions (unit Ami) may attract exploration interest as Sand 18 390 Portage Wilson information drawn from U.S. Geological Survey 7.5-minute topographic The mining shafts shown on this map are ones that could be located with some degree Lake Lake Lake 360 375 Lake quadrangles (Minnesota Department of Transportation, 2004). Inactive, analogues to Archean mafi c intrusions in Ontario, which are known to host mineralization 18 of confi dence using historical maps and published reports. Not all shafts are shown, and of platinum-group elements. 390 depleted, and reclaimed pits are shown by a line through the pit symbol. the shafts that are shown are located with varying degrees of confi dence. In particular, the er 390 Riv 390 location of the former Brainerd–Cuyuna underground mine, located at the southern edge of CRUSHED ROCK AGGREGATE Perch Grave Rice 390 OTHER QUATERNARY MINERAL ENDOWMENTS Lake Lake 390 Lake 36 the city of Brainerd, is poorly constrained. The other shaft locations shown on the South 36 31 36 390 With the possible exception of rock contained in waste dumps adjacent to open-pit 210 36 31 31 Round Clay—Clay deposited in Glacial Lake Brainerd (see Plate 3) was used in the past in range were located with the aid of historic maps on fi le at the Minnesota Geological Survey, Baxter 390 Scott Lake mines, there is no potential for any bedrock-derived aggregate in Crow Wing County due 360 375 Lake Brainerd for the manufacture of brick (Nelson and others, 1990). However, due and are mapped with more certainty. The locations of mine shafts on the Cuyuna North range to the thick cover of glacial deposits. 390 to undesirable carbonate content in the clay, texture variability, and accessibility were taken directly from those shown on maps by Schmidt (1963); these shafts may have Kenney T. 133 N. 375 issues, brick-making is not likely to resume in Crow Wing County. been overrun by open-pit mines. The extent of the open-pit mines is mapped on Plate 2. Waste-rock tailings from the Mesabi Iron Range in northeastern Minnesota have been 6 390 Lake 1 1 6 used on a limited basis for crushed-rock aggregate applications, and testing has shown that 1 6 1 Marl—Marl is composed largely of calcium carbonate dissolved from sediments The Cuyuna iron range has long been subdivided into three separate areas—the Emily 375 they may be suitable for more widespread use (Zanko and others, 2003). However, the Mesabi 360 and transported mostly by ground water to nearby lakes and bogs, where it is district, the North range, and the South range—based on contrasting lithologic and structural Island ippi range tailings are already crushed to a suitable size as part of the ore-concentrating process, Lake Miller deposited through chemical and/or biochemical precipitation. In general, the attributes of the iron-formation and associated rocks (Schmidt, 1963). The South range Mississ Lake are readily available in large quantities, and possess physical properties that meet aggregate Borden lighter the color, the higher the calcium content of a marl deposit. Marl is used has been extensively explored, and ore has been extracted from a few underground mines Bass Upper South 375 Lake test standards. In contrast, waste rock from the Cuyuna range is of mixed composition, Lake Russell Long Lake for improving soil for agriculture, and in the past was used in road construction. from this area within Crow Wing County. The North range has been the focus of intense 25 390 consisting dominantly of variably weathered, soft, phyllitic and schistose rocks. A thorough Lake 18 Crow Wing County has more than four times as many marl deposits as any exploration activity, and several underground and open-pit mines operated there for a period 375 study of the waste dumps on the Cuyuna range was not conducted for this project because 360 other county in the state (Schwartz, 1959). Although not mapped in this atlas of years. The Emily district has been thoroughly explored, but never mined. 390 Garrison of the small chance of encountering suitable material. However, these waste piles cannot 360 Mille because they are generally concealed below peat, numerous marl deposits in CROW WING HISTORY OF MINING ON THE CUYUNA IRON RANGE be completely dismissed as an aggregate source, and they may present opportunities as a LONG LAKE MAPLE GROVE 405 Lacs the county are delineated in Schwartz (1959). 375 GARRISON 390 CASS COUNTY 371 Lake local aggregate source for specialized aggregate needs. 390 405 Peat—Mapped on Plate 3 (unit pe), peat deposits are widespread across the county. The Cuyuna iron range is contained almost entirely within Crow Wing County. The 390 T. 44 N. South Peat is mined elsewhere in Minnesota primarily for horticultural purposes. range extends from west-central Aitkin County southwest through Crow Wing County into REFERENCES 405 390 375 Long Morrison County, a distance of 65 miles (105 kilometers). The Cuyuna range produced Lake 169 Beltrame, R.J., Holtzman, R.C., and Wahl, T.E., 1981, Manganese resources of the Cuyuna range, REFERENCES iron ore for almost 80 years, during which time more than 106 million tons of iron ore were 405 east-central Minnesota: Minnesota Geological Survey Report of Investigations 24, 22 p. Jack Pine 390 shipped (Skillings Minnesota Mining Directory, 2001). Production peaked in 1953, when Lake 390 Arneman, H.F., Hanson, L.D., Hermanson, H.P., and Hilde, D., 1965, Soil survey of Crow T. 44 N. the annual production was 3.9 million gross tons of ore (Schmidt, 1963). McSwiggen, P.L., Morey, G.B., and Cleland, J.M., 1995, Iron-formation protolith and genesis, 390 Wing County, Minnesota: U.S. Soil Conservation Service Series 1957, no. 21, 40 p., scale Cuyuna range, Minnesota: Minnesota Geological Survey Report of Investigations 45, 54 p. 405 The following history of the Cuyuna range is summarized from Schmidt (1963). The 1:20,000. Schmidt, R.G., 1963, Geology and ore deposits of the Cuyuna North range, Minnesota: U.S. 405 name Cuyuna is said to have come from a combination of the name Cuyler Adams, a pioneer Smith Lake Minnesota Department of Transportation, 2004, Aggregate unit: St. Paul, Minn.,

AITKIN COUNTY mnroad.dot.state.mn.us/geotechnical/aggregate/aggregate/asp>. Long 405 buried iron ore in the Cuyuna range were noted in 1859 by the defl ection of survey lines Skillings Minnesota Mining Directory, 2001, Skillings Minnesota mining directory: Duluth, 40 Lake Lake Nelson, S.L., Oberhelman, M.W., and Olson, D.J., 1990, Inventory of industrial mineral pits and 5 390 recorded by land surveyors. The fi rst systematic attempt to trace the lines of magnetic Minn., Westmorelandfl int Publishing, 184 p. 360 31 36 46°15' quarries in Minnesota: Minnesota Department of Natural Resources, Division of Minerals attraction produced by iron-formation was during the years 1875 and 1876, and again in Zanko, L.M., Niles, H.B., and Oreskovich, J.A., 2003, Properties and aggregate potential of coarse 46°15' 36 31 36 31 390 36 31 390 Report 282, 2 v. 36 1882; a hole was drilled near Brainerd in 1893 without fi nding iron ore. In 1895, Cuyler taconite tailings from fi ve Minnesota taconite operations: Natural Resources Research Resources and Reserves Committee, 1999, A guide for reporting exploration information, Adams conducted extensive dip-needle surveys, and in 1903 iron was discovered by drilling Institute Technical Report NRRI/TR-2003/44, 227 p. 405 Crow mineral resources, and mineral reserves: Littleton Colo., report submitted to the Board of in sec. 16, T. 46 N., R. 28 W. (number 1 on map). The fi rst discovery of ore-quality iron was Wing 1 390 Directors, Society for Mining, Metallurgy and Exploration, 17 p. 6 1 6 1 6 1 6 Camp 1 in 1904 in sec. 20, T. 46 N., R. 28 W. (2), in what is now referred to as the Cuyuna South Lake Lake 375 Schwartz, G.M., 1959, Investigation of the commercial possibilities of marl in Minnesota: range. That same year, drilling started on the North range in sec. 30, T. 47 N., R. 28 W. (3) 360 375 375 375 Office of the Commissioner of Iron Range Resources and Rehabilitation, 190 p. near the Kennedy mine, and the fi rst mine shaft to reach bedrock was constructed there in COUNTY 5 River 40 1908. The fi rst ore from the Cuyuna range was shipped by railroad from stockpiles at the

390 DESCRIPTION OF MAP UNITS AND SYMBOLS Mud 375 Kennedy mine in 1911. The last ore was shipped in 1984, from the Zeno mine (sec. 28, T. ISON 1 Lake Spall materials are rock particles that will cause a pop-out in hardened concrete or bituminous Plate 2 contains a complete description of the map units. Nokasippi 390 47 N., R. 29 W. [4]; Skillings Minnesota Mining Directory, 2001). Mining activity peaked Round pavement. Maximum permissible spall materials allowed by the Minnesota Department of between the years 1912 and 1914 when 32 mines were in operation, mostly in the North

MORR 375 PALEOPROTEROZOIC Lake Transportation in coarse-grained aggregate for concrete used in highway construction, by weight range, due to demand for manganiferous iron ore. In 1924, 41 miners were killed when FORT RIPLEY 360 ROOSEVELT percent of total sample, are: 0.7 percent shale, 0.3 percent soft iron oxide particles, and total spall ST MATHIAS DAGGETT BROOK PLATTE LAKE 390 mud and water fl ooded the Milford mine.  0 390 Whitefish Bedrock unit p—Small ultramafic intrusions. 39 Erskine materials (shale and iron oxide, plus unsound chert, coal, and clayey limestone) no more than 1.5 Lake Twentytwo Lake 375 Lake percent. Maximum permissible total spall materials in bituminous pavement is 5.0 percent. MANGANESE RESOURCES OF THE CUYUNA RANGE T. 43 N. Brook T. 43 N. Bedrock unit vs—Carbonaceous argillite, locally pyritic. ett Manganiferous iron-formation occurs in the Cuyuna North range, mainly in the Trommald Formation, in small lenses of iron-formation in the underlying Rabbit Lake Formation, 360 Dagg Mud Table 1. The potential for sand and gravel resources in Crow Wing County. Iron-formation, undivided. Lake Bass 390 and in the iron-formation of the Emily district. Beltrame and others (1981) estimated a Lake 390 405 minimum resource of 170 million metric tons of manganiferous ore with an average grade Primary Secondary Tertiary of approximately 10 weight percent manganese, and a more demonstrated resource of 9.1 Sedimentary rocks of the Cuyuna North and South ranges. Mud 390 390 360 Lake sand and gravel million metric tons of manganese metal for the Cuyuna range. 360 390 Bulldog Lake thickness (feet) 20–50 or greater 0–40 or greater 0–20 or greater Bedrock unit du—Subvolcanic mafic intrusive rocks in the Cuyuna South Rock POTENTIAL EXPLORATION FOR NON-FERROUS METALS 390 Lake overburden range. Probably more abundant than indicated on map. Sebie 390 Platte   Lake 360 thickness (feet) less than 5 less than 10 less than 20 Outside of drilling targeted specifi cally at magnetic anomalies produced by the linear Bedrock units vm and rv—Mafic volcanic rocks, largely fragmental. Lake 405 COUNTY LACS MILLE 375 retained on iron-formation layers in the Cuyuna range, very little exploratory drilling has been conducted Probably more abundant than indicated on map. 36 31 36 31 36 375 36 31 375 390 31 #4 sieve greater than 20% greater than 15% less than 15% in Crow Wing County specifi cally, and in all of east-central Minnesota in general. Overall, 345 375 36 Long Hannah ARCHEAN Lake Lake the fold-and-thrust belt area of east-central Minnesota (Plate 2, Fig. 1) has experienced only depth to water localized and sporadic exploration for mineral deposits other than iron and manganese. Bedrock unit Ami—Mafic intrusions. R. 32 W. 94°15' R. 31 W. 94°00' R. 29 W. R. 28 W. MORRISON COUNTY table (feet) greater than 20 greater than 10 0–20 or greater R. 30 W. Nevertheless, some mineral potential may exist, as described below. Digital base modified from the Minnesota Department of probability very high to high to moderate high to moderately low Bedrock unit Ag—Subvolcanic gabbroic rocks. Transportation BaseMap data; digital base annotation by high Paleoproterozoic mafi c intrusions the Minnesota Geological Survey. Every reasonable effort has been made to ensure the accuracy of the GIS compilation by R.S. Lively Several small mafi c intrusions of Paleoproterozoic age, recognized by distinctive, total spall1 <1.5% <1.5% <5% <1.5% <5% Elevation contours were derived from the U.S. Geological factual data on which this map interpretation is based; however, the Edited by Lori Robinson positive aeromagnetic anomalies, have been drilled by explorationists searching for diamonds Bedrock units Amv and Agm—Mafic volcanic rocks; includes possible iron- Minnesota Geological Survey does not warrant or guarantee that there are Survey 30-meter Digital Elevation Model (DEM) by the Min- quality very good very good good to very good good to SCALE 1:100 000 no errors. Users may wish to verify critical information; sources include in many of the counties surrounding Crow Wing County. To date, none of these sampled formation and subvolcanic mafic intrusive rocks. nesota Geological Survey. to good to good moderate to good moderate 1 0 1 2 3 4 5 MILES both the references listed here and information on fi le at the offi ces of intrusions have been known to yield diamonds. They may be potential hosts for other types Limited potential for bedrock resources—The unshaded portions of the map Universal Transverse Mercator Projection, grid zone 15 the Minnesota Geological Survey in St. Paul. In addition, effort has of mineralization, such as platinum-group elements or base-metal sulfi des, and thus may be 1983 North American Datum 1 0 1 2 3 4 5 6 7 8 KILOMETERS been made to ensure that the interpretation conforms to sound geologic indicate areas underlain by bedrock units that have little or no potential and cartographic principles. No claim is made that the interpretation further explored. A few of these intrusions are inferred from aeromagnetic data to be present for significant minerals exploratory activites based on current  shown is rigorously correct, however, and it should not be used to guide in southern Crow Wing County (unit p), but none have been verifi ed by drilling. knowledge and models of mineralization. CONTOUR INTERVAL 15 METERS engineering-scale decisions without site-specifi c verifi cation. Archean rocks Location of mine shaft. ©2004 by the State of Minnesota, Department of Natural The Archean supracrustal rocks in northwest Crow Wing County, with the exception of Inferred fault. Re sources, and the Regents of the Uni ver si ty of Minnesota two or three drill holes along the eastern edge, are completely unexplored. Meager drilling LOCATION DIAGRAM Inferred thrust fault. The University of Minnesota is an equal op por tu ni ty ed u ca tor data in and adjacent to the county, and extrapolation of known geology from outside the Iron-formation inferred from linear aeromagnetic anomalies. and employer GEOLOGIC ATLAS OF CROW WING COUNTY, MINNESOTA county by interpretation of aeromagnetic data, imply that a substantial portion of these