Bedrock Geology of Dixon West Quadrangle

STATEMAP Dixon West-BG

Lee County, Illinois

Dennis R. Kolata 2013

Prairie Research Institute ILLINOIS STATE GEOLOGICAL SURVEY 615 East Peabody Drive Champaign, Illinois 61820-6964 (217) 244-2414 http://www.isgs.illinois.edu © 2013 University of Illinois Board of Trustees. All rights reserved. For permission information, contact the Illinois State Geological Survey. INTRODUCTION STRATIGRAPHY The Dixon West Quadrangle is situated in northwestern Lee Bedrock in the Dixon West Quadrangle consists largely of County, Illinois. It encompasses the western parts of the city Ordovician dolomite and shale and a small area of Silurian of Dixon, which is the largest town in the county. Most of the dolomite in the southwestern part of the quadrangle. It has land is used for agricultural purposes but a moderate amount been standard practice of the ISGS during the past few of residential and commercial developments are present. decades to follow the Ordovician classification and nomen- clature proposed by Templeton and Willman (1963). Their The quadrangle lies in the Rock River Hill Country of the stratigraphy was followed in large part by Willman and Ko- Central Lowlands Province. The topography formed primar- lata (1978) who made minor revisions to some members and ily by deposition of glacial sediments (clay, silt, sand, and documented the presence of nine widespread K-bentonite gravel) in a till plain which was subsequently dissected by beds. These stratigraphic investigations have shown that the erosional processes of the Rock River and its tributaries. Upper Ordovician carbonate succession consists of distinc- Bedrock in the Dixon West Quadrangle is largely concealed tive rock units that can be traced over wide areas of the beneath the till plain except for local exposures along the riv- Midcontinent U.S. Correlation of rock units is based largely er bluffs and tributary ravines. The glacial deposits range in on 1) relative amount of disseminated clay, 2) chert content, thickness from 0 to 50 feet throughout most of the quadran- 3) widely traceable K-bentonite beds, and 4) hardground gle but reach thicknesses of 100 feet in buried stream valleys omission surfaces. These were the primary features used to in the southern parts of the quadrangle (Piskin and Berg- subdivide the Platteville and Galena carbonate succession strom 1975). Bedrock formation contacts are largely inferred into 1 megagroup, 2 groups, 3 subgroups, 10 formations, 32 because of the widespread surficial cover. Surface elevations members, and 9 beds. In the outcrop area of northern Illinois range from 820 feet near Palmyra to 650 feet along the banks where the type sections for many of the subdivisions occur, of the Rock River. the succession ranges from a mere 300 to 350 feet thick. Compared to other Paleozoic rock units, the Illinois Up- Compilation of this map is based on examination of bedrock per Ordovician carbonate succession is one of most highly exposures in quarries, road excavations, railroad cuts, and subdivided units in North America. Many of the formations natural exposures along streams and waterways. Subsurface are too thin to map at the current scale of 1:24,000, therefore information was obtained from water well records and drill do not meet the ‘test of mappability’ recommended in the cuttings filed at the Illinois State Geological Survey (ISGS). North American Stratigraphic Code (1983). Furthermore, the Wireline logs were not available in the Dixon West region ranks of ‘megagroup and subgroup’ are not recognized in the during this field investigation. Two reference wells situated Code (1983). Based on these facts, adjustments in the ranks within three miles of the eastern boundary of the map in the of the Illinois Upper Ordovician lithostratigraphic units are adjacent Dixon East Quadrangle provided valuable insight to warranted. The simplest way to bring the Templeton and the stratigraphic succession. These include the City of Dixon Willman (1963) and Willman and Kolata (1978) classifica- water well No. 10 (IP 121032353400); SW SW NW Sec. tion schemes up to code and to maintain the usefulness of 16, T21N, R9E; latitude N41° 489 3499 and longitude W89° the numerous recognized units is to reassign the ranks of the 289 3599; total depth 1,748 feet) and the Dixon State School lithostratigraphic units. It is here proposed that the revised well No. 3 (IP 121030009200; SW SW SW Sec. 21, T22N, classification would: R9E; Latitude N41.874675 and Longitude W89.472851; • eliminate the megagroups and subgroups, total depth 1,965 feet). Drill cuttings and gamma ray logs are • reassign Ottawa megagroup to the rank of group available for both wells. • reassign Platteville, Decorah, and Galena groups to formations The bedrock in Lee County was illustrated very generally on • reassign Pecatonica, Mifflin, Grand Detour, Nachusa, published state-wide geologic maps (Worthen 1875, Weller and Quimbys Mill formations to members of the Plat- 1906, 1912, 1917, Weller et al. 1945, 1961, Willman et al. teville Formation 1967, Kolata et al. 2005). One of the first concerted efforts to • reassign Spechts Ferry, Kings Lake and Guttenberg map in the area was done by Templeton (1940). His detailed formations to members of the Decorah Formation report on the Woosung quadrangle (1:48,000 scale) includes • reassign Dunleith, Wise Lake, and Dubuque forma- bedrock descriptions for the northern parts of the Dixon tions to members of the Galena Formation West Quadrangle. The most recent effort to map the bedrock • reassign all 32 corresponding members to beds is the countywide work of McGarry (1999). Stratigraphic • keep the nine named K-bentonite beds (Willman and and structural investigations in the Dixon area include those Kolata 1978) at bed rank (fig. 1). by Templeton and Willman (1952, 1963), Kolata and Busch- bach (1976), Willman and Kolata (1978), and Kolata et al. Likewise, the Maquoketa group is reassigned to rank of (1978), Kolata and Graese (1983). formation and the Cape, Scales, Fort Atkinson, Brainard, and

1 Templeton and Willman (1963) Willman and Kolata (1978) Present Report OUP OUP E E E OUP OUP K-BENTONITE TION K-BENTONITE OUP OUP OUP GR GR AG AG AG FORMATION MEMBER FORMATION MEMBER MEMBER BED BED BED ST ST ST GR GR GR SERIES SERIES SERIES SUBGR SUBGR FORMA MEGA MEGA

Dubuque Dubuque Dubuque

Stewartville Stewartville Stewartville Wise Lake Wise Lake Wise Lake Sinsinawa Sinsinawa Dygerts Sinsinawa Dygerts Edenian

Wyota Wyota Cincinnatian Wyota Wall Haldane k k Wall Wall Haldane rk Nasset rk wic wic Sherwood Sherwood Sherwood Nasset Conover Conover Rivoli Rivoli es Pa Rivoli es Pa v Calmar v Calmar Galena Lo Lo Kimms Kimms Dunleith Mortimer Dunleith Mortimer Dunleith Mortimer entonia n entonia n Galena Fairplay Galena Fairplay Fairplay Tr Tr Eagle Point Eagle Point Eagle Point Beecher Beecher Beecher

St. James St. James Chatfieldian St. James Buckhorn Buckhorn Buckhorn Glenhaven Glenhaven Dickeyville Glenhaven Dickeyville Guttenberg Guttenberg Elkport Guttenberg Elkport Garnavillo Garnavillo Garnavillo Glencoe Glencoe Glencoe

Spechts Ferry Spechts Ferry Millbrig Decorah Spechts Ferry Millbrig Decorah Castlewood Decorah Castlewood Castlewood Deicke Deicke Strawbridge Strawbridge Strawbridge Quimbys Mill Shullsburg Quimbys Mill Shullsburg Quimbys Mill Shullsburg wa wa wa Hazel Green Hazel Green Hazel Green Otta Otta Otta Everett Everett Everett

Champlainian Nachusa Elm Champlainian Nachusa Elm Nachusa Elm Eldena Eldena Eldena Forreston wkian

Victory Forreston Moha Forreston Hely Grand Detour Grand Detour Grand Detour Plattin

Clement Plattin Stillman Stillman Stillman inian eran eran r ville ville ville

iv Walgreen iv

Cowen Tu Cowen kr Dement kr Platte Platte Platte Blac Briton Blac Hazelwood Mifflin Establishment Mifflin Mifflin Brickeys Blomeyer Oglesby Oglesby Oglesby Medusa Medusa Medusa New Glarus New Glarus New Glarus Pecatonica Pecatonica Pecatonica Dane Dane Dane Chana Chana Chana Hennepin Hennepin Hennepin

Figure 1 Comparison of the proposed lithostratigraphic classification of the Platteville and Galena carbonate rocks in northern Illinois with that of Templeton and Willman (1963) and Willman and Kolata (1978).

Neda formations to rank of members. The series and stage 3 inches, are stained by iron-rich minerals, and are back- names as well as boundaries are also updated in recognition filled with sediment from the overlying unit (Kolata et al. of the recent advancements in Ordovician chronostratigra- 1998, 2001). Some of the more significant surfaces include phy. 1) approximately 15 to 20 surfaces in the lower part of the Dunleith Member, 2) top of the Guttenberg Member, 3) top The stratigraphic units that are known to occur at the bed- of the Quimbys Mill Member 4) top of the Mifflin Member, rock surface in the quadrangle include the Upper Ordovician 5) top of the Pecatonica Member and 6) two or three surfaces Platteville, Galena, and Maquoketa Formations and Silurian in the lower 10 feet of the Pecatonica. Mosalem Formation. All were deposited in intertidal to subtidal marine environments. The Platteville and Galena STRUCTURAL GEOLOGY Formations consist mainly of dolomite. Several hardground omission surfaces within the Galena and Platteville are wide- The Dixon West Quadrangle is situated in a structurally spread and persistent. They are readily identified in outcrop complex area northern Illinois near the termination of and drill core and are useful in correlating this part of the the Sandwich Fault Zone, Plum River Fault Zone and the stratigraphic column. These planar surfaces are character- projected trend of the La Salle Anticlinorium (fig. 2). Lying ized by irregular solution cavities, mainly less than 2 inches parallel to and south of the Sandwich Fault Zone in Lee and across. They penetrate the bedding planes to depths of 2 to Ogle Counties is the Ashton Anticline. This broad anticline

2 Ashton Dixon West Anticlin Quadrangle e LEE

Illinois Basin

Figure 2 Structural configuration of Cambrian Franconia Formation in northern Illinois showing Dixon West Quadrangle relative to major structural features (compiled by Janis D. Treworgy and published in Kolata and Graese 1983). Note the regional southwestward dip within and adjacent to the Dixon West Quadrangle. brings Middle Ordovician and Upper Cambrian rocks to the ECONOMIC RESOURCES bedrock surface along the south side of the Sandwich Fault Zone northeast of the Dixon West Quadrangle and is respon- Dolomite sible for the subtle southwestward dip of bedrock within the In northern Illinois the Platteville and Galena dolomite is quadrangle. widely quarried for use as aggregate, road surfacing mate- rial, agricultural lime, and rip-rap. Active quarries in the One of the more notable structures in the quadrangle is an Dixon West Quadrangle include those on the southwest side anticline that strikes 340 degree NW. Dip on the NE limb of Dixon, Illinois (N½ Sec. 7, T21N, R8E) and northwest of was measured at 5 degrees but the dip of the SW limb could Palmyra (NW Sec.33 T22N, R8E). not be measured. The northeast trending dip is obvious in an abandoned quarry on the west side of Rock Island Road Groundwater (NE Sec. 12, T21N, R8E) (fig. 3). The anticline is confirmed Residential wells in the Dixon West Quadrangle recover by the presence of the Platteville Formation at the bedrock groundwater largely from fractured dolomite in the Plat- surface in several water wells on the south side of Rock Is- teville and Galena Formations or from the underlying St. land Road (SE Sec. 12, T21N, R8E) and on the north side of Peter Sandstone. Most of these wells are drilled in the range Rock River (SE Sec. 11, T21N, R8E). The Platteville-Galena of 150 to 300 feet deep. Municipal wells in the area tend to contact is exposed at water level in the high bluff on the draw water from Cambrian sandstone aquifers at depths of south side of Rock River (SW SE Sec. 11, T21N, R8E). The approximately 1800 feet. structure is here referred to as the Bloody Gulch Anticline in reference to Bloody Gulch Road which runs through the area ACKNOWLEDGMENTS of the anticline. We thank the numerous landowners who allowed us onto Bedrock fracture patterns indicate dominant northwest and their land for outcrop study. Jacquelyn L. Hannah provided subdominant southwest trends similar to other regions of field assistance. Special thanks go to Donald E. Luman for northern Illinois (McGarry 2000). the Lidar maps and to Jane E. Johnshoy Domier for the graphic and cartographic layout and design. 3 Figure 3 Abandoned quarry on southwest side of Dixon (NE Sec. 12, T21N, R8E) showing prominent northeastward dip of Platteville rocks. This research was supported in part by the U.S. Geological Kolata, D.R., W.D. Huff, and S.M. Bergström, 2001, The Or- Survey National Cooperative Geologic Mapping Program dovician Sebree Trough: An oceanic passage to the Mid- (STATEMAP) under USGS award number G12AC20408. continent United States: Geological Society of America The views and conclusions contained in this document are Bulletin v. 113, no. 8, p. 1067–1078. those of the authors and should not be interpreted as neces- McGarry, C.S., 1999, Bedrock geology of Lee County, Il- sarily representing the official policies, either expressed or linois: Illinois State Geological Survey, OFS 1999-1e implied, of the U.S. Government. Lee BG. McGarry, C.S., 2000, Regional fracturing of the Galena- REFERENCES Platteville aquifer in Boone and Winnebago Counties, Illinois: geometry, connectivity and tectonic signifi- Kolata, D.R. 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