BEDROCK GEOLOGY OF SELMA QUADRANGLE Illinois Department of Natural Resources ILLINOIS STATE GEOLOGICAL SURVEY MONROE COUNTY, ILLINOIS STATEMAP Selma-BG William W. Shilts, Chief F. Brett Denny and Joseph A. Devera 2002 AЈ o e Msm Mw Msm 7 3 G 7 H " 490 Msm Msm Monroe City Syncline Msl Msm Mbkfg Msm Mw EXPLANATION Msl St. Louis Limestone Ou Msm Salem Limestone e" 195 e" Mississippian Valmeyeran 60 o Mw Warsaw Shale 5 Burlington and Keokuk 64 Mbkfg Limestones and e" 45e" Msm Fern Glen Formation 105 e" Unconformity Mw Ordovician Mohawkian Ou Ordovician undifferentiated 38 e" Msm e" Msl 58 Symbols 665" Strike and dip of bedding; number 40 indicates degree of dip Æ Horizontal bedding Ç Abandoned quarry Drill Holes from which subsurface data were obtained Mbkfg e" Oil well A e" Water well 109 e Numeric label indicates total depth of boring in feet. Line Symbols dashed where inferred Contact G Syncline H direction of plunge indicated by arrows A AЈ Line of cross section Note: Well and boring records are on file at the ISGS Geological Records Unit and are available online from the ISGS Web site. Ou e" 43 Base map compiled by Illinois State Geological Survey from digital data (Raster Featrue SCALE 1:24,000 Geology based on field work by B. Denny and J. Devera, 2001–2002. Separates) provided by the United States Geological Survey. Compiled from imagery dated 1 1/ 2 0 1 MILE 1962. Revised from imagery dated 1993. PLSS, survey control, contours and elevations Digital cartography by J. Domier, B. Denny, and S. Radil, Illinois State Geological Survey. 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET current as of 1962. Map edited 1996. 1 .5 0 1 KILOMETER This research was supported in part by the U.S. Geological Survey National Cooperative North American Datum of 1983 (NAD 83) Geologic Mapping Program (STATEMAP) under USGS award number 01HQAG0103. The Projection: Transverse Mercator views and conclusions contained in this document are those of the authors and should not 10,000-foot ticks: Missouri (east zone) and Illinois (west zone) State Plane Coordinate be interpreted as necessarily representing the official policies, either expressed or implied, system, (Transverse Mercator) BASE MAP CONTOUR INTERVAL 20 FEET of the U.S. Government. 1,000-meter ticks: Universal Transverse Mercator grid system, zone 15 SUPPLEMENTARY CONTOUR INTERVAL 5 FEET NATIONAL GEODETIC VERTICAL DATUM OF 1929 This map has not undergone the formal Illinois Geologic Quadrangle map review pro- cess. Whether or when this map will be formally reviewed and published depends on the Recommended citation: Released by the authority of the State of Illinois: 2002 resources and priorities of the ISGS. Denny, F.B., and J.A. Devera, 2002, Bedrock Geology of Selma Quadrangle, Monroe County, Illinois: Illinois State Geological Survey, USGS-STATEMAP contract report, 2 The Illinois State Geological Survey, the Illinois Department of Natural Resources, and the sheets, 1:24,000. State of Illinois make no guarantee, expressed or implied, regarding the correctness of the interpretations presented in this document and accept no liability for the consequences of decisions made by others on the basis of the information presented here. The geologic interpretations are based on data that may vary with respect to accuracy of geographic location, the type and quantity of data available at each location, and the scientific and technical qualifications of the data sources. Maps or cross sections in this document are not meant to be enlarged. 1 /2 ° ROAD CLASSIFICATION ADJOINING 1 2 3 QUADRANGLES 1 Herculaneum TH Primary highway, Light-duty road, hard or 2 Valmeyer TH hard surface improved surface DRAFT: 3 Waterloo 4 5 Secondary highway, 4 Festus UE NOR hard surface Unimproved road THIS MAP HAS NOT BEEN REVIEWED GNETIC NOR 5 Renault TR For more information contact: 6 Halifax MA Illinois State Geological Survey 6 7 8 7 Danby AND IS NOT YET PUBLISHED 615 East Peabody Drive APPROXIMATE MEAN 8 Bloomsdale Interstate Route U.S. Route State Route Champaign, Illinois 61820-6964 DECLINATION, 2008 (217) 244-2414 http://www.isgs.uiuc.edu STATEMAP Selma-BG Sheet 1 of 2 THICKNESS FORMATION GRAPHIC COLUMN A St. Louis Limestone Limestone, siltstone, limestone Subsurface Only (feet) UNIT breccia, and shale. Light-gray to medium-gray dense lime- SERIES SYSTEM mudstone with fossil wackestones. Part of the unit contains D Burlington and Keokuk Limestone Limestone, chert, quartz sand and subangular limestone breccia clasts. Oolitic siltstone, and shale. Light-gray to white crinoidal grainstones grainstones, greenish oncolitic packstones, peloidal grainstones, dominate and are interbedded with nodular and bedded light- stromatolitic boundstones, carbonate intraclastic conglomerates gray to black cherts. The cherts, which comprise at least 25 St. Louis 150–200 A make up a highly variable mix of microfacies. Yellowish dolostone percent of the lowermost beds are white when weathered, Limestone Acrocyathus beds are also present in this formation. Gray to dark-gray chert and some have bioclasts of crinoids and brachiopods. Sandy floriformis zone occurs as nodules and stringers. Siltstones are calcareous and limestones weather light brown, are cross-bedded, and contain greenish. The shales are greenish gray and reddish brown, brachiopod and crinoid molds. The unit is characterized by calcareous, soft, and non-fissile. Acrocyathus floriformis, a alternating layers of light gray to white crinoidal grainstones with Salem colonial coral, occurs in the upper part of the basal portion of this beds of argillaceous and sandy limestones. Large spirifers are 120–150 B Limestone formation. Acrocyathus floriformis is widespread near the base common along with crinoids, bryozoans, and corals. Siltstones of the unit. The contact with the underlying unit is unconformable are dark gray with a greenish tint and are calcareous. The unit is but difficult to identify due to lithologic similarities of the two conformable with the underlying unit. units. The contact was placed about 20 feet below the lower Warsaw Acrocyathus floriformis zone. Locally an erosional karstic surface E Fern Glen Formation Limestone, siltstone, and shale. 90–110 C Shale can be observed between these units. Limestone is red to greenish gray, thin-bedded, and argillaceous; it contains small calcite geodes and crinoid stems. Green and B Salem Limestone Limestone, dolomite, chert, and siltstone. red shaly calcareous siltstones are diagnostic. The cherts ALMEYERAN Limestones are tan-brown to light gray and contain laminated are greenish gray, nodular, and fossiliferous. The basal part is V MISSISSIPPIAN tidallites, wackestones to grainstones composed of rounded and unconformable with the underlying formation. broken fossils and coated grains to gray lime-mudstones similar to the overlying St. Louis Limestone. Bedding styles range from F Maquoketa Formation Dolostone, siltstone, mudstone. Burlington- tabular to undulatory. Cross-beds are present in grainstone This unit is poorly exposed and forms gentle hill slopes that are Keokuk 100–150 D Limestone facies. The unit has a dirty gray-brown grainy appearance. The well vegetated. The lower part of the formation is calcareous diagnostic character of this formation is alternating beds of and grades upward into bluish green, thin calcareous siltstones laminated, fine-grained (calcisiltite) facies with coarse bioclastic, interbedded with bluish gray mudstones. The upper part is shaly peloidal to oolitic grains in shoaling-upward cycles. Dolomites buff-gray to greenish gray and has interlaminated silts and are brown and have moldic porosity. Cherts are light gray and shales. This unit is unconformable with the underlying units. may be bioclastic and weather with a porous rind. Cherts occur Fern Glen between grainstones and laminated beds as elliptical nodules G Kimmswick Limestone–Trenton Limestone in the 30–50 E Formation containing concentric rings that spall off like egg shells when subsurface Limestone, dolostone, and minor shale. White weathered. Siltstones are brown to light gray and thinly bedded, to gray, coarsely crinoidal grainstone is the dominant facies in typically less than 1 inch thick. Oolitic beds are rare. The this formation. Fossils include Receptaculites sp., Illaenus sp., Maquoketa Foraminifera fossil invertebrates include spiriferid and productid Isotelus gigas (trilobites), brachiopods, and gastropods that are 50–80 F Formation brachiopods, rugose corals, conularids, and crinoids. Ramose, commonly broken in the cross-bedded coarse bioclastics of the fenestrate, encrusting, and bifoliate bryozoans are also present. formation. Shales are calcareous and may contain pyrite. Cherts TIAN The contact with the underlying unit is gradational. are not very common and are white with slight yellow tones. When cracked, the limestones have a faint petroliferous odor. C Warsaw Shale Dolomitic limestone, siltstone, and mudstone. The basal contact is a distinct hardground omission surface. Kimmswick 80–110 G Medium-gray, crinoidal, bryozoan wackestones and packstones CINCINNA Limestone that contain a few brachiopods. Dolostone beds are gray-brown, H Decorah Formation Limestone and shale. Light brownish to thinly bedded, and contain chlorite-rich shale clasts. The upper greenish limestone or lime mudstone interbedded with organic- VICIAN half of the unit is dominated by shaly limestone and dolostone rich reddish brown shales. The cherts are dark gray, and the Decorah 20–40 H beds. The lower half contains bluish gray mudstones