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CARBONATE PLATFORM FACIES AND FAUNAS OF THE MIDDLE AND UPPER DEVONIAN CEDAR VALLEY GROUP AND LIME CREEK FORMATION, NORTHERN IOWA Iowa Geological and Water Survey Guidebook Series No. 28 Iowa Department of Natural Resources Richard Leopold, Director October 2008 COVER Lithographic plate of Idlewild Member of Lithograph City Formation at Lewis Quarry, immediately south of Osage, Mitchell County, Iowa. Beds marked “X” are those determined by A. Hoen & Co. of Baltimore to be suitable for use in lithography. Reproduced from Plate VIII in Iowa Geological Survey Annual Report for 1902. Printed in-house on recycled paper. CARBONATE PLATFORM FACIES AND FAUNAS OF THE MIDDLE AND UPPER DEVONIAN CEDAR VALLEY GROUP AND LIME CREEK FORMATION, NORTHERN IOWA Iowa Geological and Water Survey Guidebook Series No. 28 Prepared for the 69th Annual Tri-State and Great Lakes Section – SEPM Fall Field Conference Co-hosted by the Department of Earth Science, University of Northern Iowa and the Iowa Geological and Water Survey Prepared and led by John R. Groves1, James C. Walters1 and Jed Day2 with contributions by Rodney Hubsher1, Carl W. Stock3, Brian J. Witzke4 and Bill J. Bunker4 1 Department of Earth Science, University of Northern Iowa, Cedar Falls, IA 50614-0335 2Department of Geography & Geology, Illinois State University, Normal, IL 61790-4100 3Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487-0338 4Iowa Geological and Water Survey, 109 Trowbridge Hall, Iowa City, IA 52242-1319 October 2008 Iowa Department of Natural Resources Richard Leopold, Director TABLE OF CONTENTS Overview of the Lithograph City Formation . 1 John R. Groves Quaternary geology of the fi eld trip area . 7 James C. Walters The Floyd karst area . 11 James C. Walters Overview of Middle and Upper Devonian Cedar Valley Group and Lime Creek Formation carbonate platform facies, faunas and event stratigraphy of northern Iowa . 15 Jed Day, Brian J. Witzke and Bill J. Bunker Stromatoporoid biostratigraphy of the Iowa Frasnian . 43 Carl W. Stock A brief description of lithography . 53 John R. Groves FIELD TRIP STOPS – SATURDAY . 57 John R. Groves and Rodney Hubsher Stop 1 – Osage Roadcut . 57 Stop 2 – Jones Quarry . 61 Stop 3 – Steere Quarry . 65 Stop 4 – Messerly Quarry . 71 FIELD TRIP STOPS – SUNDAY . 77 Jed Day Stop 5 – Fertile Quarry . 77 Stop 6 – Williams Quarry . 81 Stop 7 – Rockford Brick and Tile Quarry – Floyd County Fossil and Prairie Center and Park Preserve . 89 ACKNOWLEDGMENTS Organizers of the combined 69th Annual Tri-State and Great Lakes Section – EPM Fall Field Conference wish to thank BMC Aggregates, L. C., Croell Redi-Mix, Inc. and Greene Limestone Company (a division of Allied Construction Co., Inc.) for permission to visit their quarries. Financial sponsorship of the fi eld conference and associated activities was provided by BMC Aggregates L.C., the Black Hawk Gem and Mineral Society, the Cedar Valley Rock and Mineral Society, the Great Lakes Section – Society for Sedimentary Geology (GLS-SEPM) and the Central Section of the National Association of Geoscience Teachers (NAGT). We are especially grateful to Dr. Brian J. Witzke, geologist with the Iowa Geological and Water Survey, for information and illustrations used in this guidebook. Brian’s work on Middle and Upper Devonian rocks in northern Iowa is the basis for our modern understanding of those units. We further wish to thank Mr. Brian Gossman, geologist with the Iowa Department of Transportation, for information on rock units being mined at many quarries throughout north-central Iowa. The Iowa Geological and Water Survey’s editorial committee expertly handled the layout and worked with the Geological Society of Iowa to print this guidebook. Additional logistical suppport for the fi eld conference was provided by the Department of Earth Science at the University of Northern Iowa, the Department of Geography and Geology at Illinois State University and the Gamma Sigma Chapter of Sigma Gamma Epsilon at the University of Northern Iowa. OVERVIEW OF THE LITHOGRAPH CITY FORMATION John R. Groves Department of Earth Science, University of Northern Iowa, Cedar Falls, IA 50614-0335 LITHOSTRATIGRAPHY fossiliferous limestone southward in the north- ern Iowa outcrop belt where stromatoporoids are The Lithograph City Formation was named very abundant locally. Accordingly to Witzke et by Witzke et al. (1988) for the package of strata al. (1988), the Osage Springs Member in northern lying disconformably above the Coralville For- Iowa varies in thickness from 3.4 to 7.5 m and it mation and disconformably below the Shell Rock is similar in thickness and lithology to the under- Formation or Sweetland Creek Shale (Fig. 1). lying Iowa City Member of the Coralville Forma- The type section of the Lithograph City Forma- tion. It is distinguished from the latter on strati- tion was designated as the old quarry adjacent to graphic position and faunal criteria. It is overlain the abandoned town of Lithograph City in Floyd conformably throughout most of its distribution County, Iowa. A new quarry (Saturday Stop #2) by the Idlewild Member, although in northwest- is operating now immediately east of the old one. ern Black Hawk County (and presumably also in Prior to 1988 these strata were assigned by most neighboring parts of Bremer and Butler counties) workers to the Coralville Formation, but they do the Osage Springs and Idlewild members are sep- not correlate with any part of the Coralville in arated by the Thunder Woman Shale Member. its type area. Recognition of the distinctness of The type section of the Thunder Woman the Lithograph City interval occurred in connec- Shale Member was designated at Yokum Quarry tion with detailed studies of Devonian aquifers in northwestern Black Hawk County, approxi- in northern Iowa (Witzke and Bunker, 1984, mately 1.4 km east of Thunder Woman County 1985). Further information on the newly recog- Park (Witzke et al., 1988). Yokum Quarry has nized Lithograph City Formation was presented since been abandoned and the site is now known in Bunker et al. (1986) and Bunker, ed. (1995). as the Turkey Ridge Wildlife Area, managed by Inner shelf facies of the Lithograph City the Black Hawk County Conservation Board. A Formation in northern Iowa are subdivided into complete section of the Thunder Woman Shale the Osage Springs, Thunder Woman Shale and Member is exposed in the currently operating Idlewild members (ascending order). In east- Messerly Quarry (Saturday Stop #4) where the central and southeastern Iowa the same interval unit is 2.5 to 3 m thick. The Thunder Woman comprises distal inner shelf and middle shelf fa- Shale Member is light grey to buff, slightly dolo- cies subdivided into the State Quarry, Andalusia mitic, unfossiliferous, silty shale. It is much less and Buffalo Heights members (Fig. 1). Only the resistant than underlying and overlying carbon- inner shelf facies are considered here. ates of the Osage Springs and Idlewild members, The Osage Springs Member is the basal unit of but dolomitic intervals are relatively well indu- the Lithograph City Formation in northern Iowa rated. The surface distribution of the member is and neighboring Minnesota. At its type section a limited to the southern part of the northern Iowa few miles south of the town of Osage in Mitchell outcrop belt. It is present also in the subsurface County (Saturday Stop #1) it consists of dolo- of central Iowa, but to the north it grades later- mite and dolomitic limestone with calcite-fi lled ally into the Idlewild Member and to the south vugs. Fossils and ghost fabrics of precursor lime- it is erosionally truncated (Bunker et al., 1986; stone lithologies are detectable in certain layers. Witzke et al., 1988). The member becomes increasingly dominated by The Idlewild Member conformably overlies 1 Figure 1. Cross section of Cedar Valley Group strata from north-central Iowa (A) to extreme southeastern Iowa (B). Exposures of the Lithograph City Formation visited on this trip represent the inner shelf facies on left side of diagram. Figure prepared and provided by B. J. Witzke. the Osage Springs Member throughout most of ly, especially in northern areas, signifying a peri- northern Iowa. Locally it overlies or grades lat- tidal origin. In the southern part of the northern erally into the Thunder Woman Shale Member. Iowa outcrop belt the unit becomes more fossil- It grades laterally into fossiliferous carbonates of iferous and peritidal features become somewhat the Andalusia Member in southeastern Iowa. The less common. The unit ranges in thickness from type section of the Idlewild Member was desig- 16 to 24 m where it is overlain by the Shell Rock nated at Floyd Quarry in northern Floyd County, Formation (Witzke et al., 1988). Its thickness is approximately 2.3 km downstream on the Cedar appreciably less where truncated beneath Pleis- River from Idlewild State Park (Witzke et al., tocene glacial deposits, as at Saturday Stops 2, 1988). The Idlewild Member comprises a hetero- 3 and 4. geneous assortment of lithologies ranging from The contact between the Idelwild Member laminated lithographic limestone and dolomite and the overlying Shell Rock Formation exhibits to calcareous shale to variably fossiliferous lime- erosional relief locally. Lithologies of the basal stone. Mudcracks, birdseyes and fenestral fabrics, Mason City Member of the latter unit are vari- evaporite molds and intraclasts are present local- ably argillaceous, skeletal and dolomitic lime- 2 Member is entirely dolomite and sparsely fos- siliferous at its type section in Mitchell County, whereas in Black Hawk County it is highly fossil- iferous (biostromal, in part) and only partly dolo- mitic. Facies changes within the Idlewild Mem- ber are equally well developed. At its northern exposures the Idlewild comprises sparsely fossil- iferous, pelletal, intraclast- and birdseye-bearing, variably laminated, fi ne-grained limestones. To the south it is more coarsely bioclastic with only minor beds of sublithographic limestone.

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