Lithostratigraphy and Depositional Environments of the Lexington Limestone (Ordovician) of Central Kentucky By EARLE R. CRESSMAN GEOLOGICAL SURVEY PROFESSIONAL PAPER 768 Prepared in cooperation with the Kentucky Geological Survey A desc1·ijJtion of a Middle and UpjJer Ordovician limestone formation and its constituent members with a discussion of facies 1·elations) environn~ents of dejJosition) and jxlleogeography UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1973 UNITED STATES DEPARTMENT OF THE INTERIOR 'ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey,. Director Library of Congress catalog-card No. 73-600094 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402. Price: paper cases-$8. 70, domestic postpaid; $8.25, GPO Bookstore Stock Number 2401-00362 . CONTENTS Page Page Abstract ---------------------------------------- 1 Stratigraphy-Continued Introduction ------------------------------------- 1 Lexington Limestone-Continued Geologic setting ____ - _--- ____ --_------------------ 8 Devils Hollow Member ------------------­ 40 11 Millersburg Member ---------------------­ 41 Stratigraphy ------------------------------------ 44 11 Clays Ferry Formation ----------------------­ Lexington Limestone ------------------------- 45 Curdsville Limestone Member ____ _: _______ _ 11 Kope Formation ----------------------------­ Point Pleasant Formation -------------------- 46 15 Logana Member ------------------------­ Fauna -----------------------------------------­ 46 Grier Limestone Member --------------··-­ 17 Age --------------------------------------------- 50 Perryville Limestone Member ------------- -:;a Facies and paleogeography ----------------------- 51 Faulconer Bed ----------------------­ 25 Summary of depositional environments -------­ 51 Salvisa Bed ------------------------­ 25 Factors governing facies distribution ---------­ 51 Cornishville Bed --------------------- 28 Facies relations -----------------------------­ 54 Tanglewood Limestone Member ----------­ JO Paleogeography -----------------------------­ 54 Brannon Member -----------------------­ 33 Relation of facies to structure ---------------- 55 Sulphur Well Member -------------------­ 37 Regional relations ---------------------------- 55 Stamping Ground Member ---------------­ 38 References cited --------------------------------- 57 Greendale Lentil ------------------------- 39 Index ------------------------------------------- 61 ILLUSTRATIONS [Plates are in pocket] PLATES 1-6. Stratigraphic sections of the Lexington Limestone. central Kentucky, showing ranges of fossils along- 1. Line A-A'. 2. Line B-B'. 3. Line C-C'. 4. Line D-D'. 5. Line E-E'. 6. Line F-F'. 7. Restored stratigraphic sections of Lexing'~n Limestone, central Kentucky. 8. Generalized composite fence diagram of Lexington Limestone and equivalent formations, central Kentucky, 1 showing facies relations. • 9. Block diagrams showing facies and paleogeography of the Lexington Limestone. 10. Stratigraphic section showing correlation of Lexington Limestone of central Kentucky with equivalent strata of southwestern Ohio. 11. Map showing paleogeography and lithofacies in the Eastern United States during Lexington time. Page FIGURE 1. Index map of central Kentucky showing location of area studied, surface extent of Lexington Lime- stone, and major structural features ------------------------------------------------------ 3 2. Maps of the report area showing lines of section and location of measured sections __ _:___________ 4 3. Diagrams showing normative mineralogy of 25 samples of the Lexington Limestone and Clays Ferry Formation ------------------------------------------------------------------------------- 10 4. Isopach map of the Lexington Limestone ------------------------------------------------------ 11 5. Photograph showing contact of Lexington Limestone and Tyrone Limestone ---------------------- 12 6. Photograph showing disconformity between Lexington Limestone and Tyrone Limestone ---------- 12 7. Map showing distribution of mud cave bentonite of drillers and approximate thickness of interval be- tween base of pencil cave bentonite. of drillers and base of Lexington Limestone -------------- 13 8. Isopach map of Curdsville Limestone Member of Lexington Limestone --------------------------- 14 9. Photograph showing interbedded calcisiltite and shale in lower part of Logana Member of Lexing- ton Litnestone --------------------------------------------------------------------------- 15 n1 IV CONTENTS Page FIGURE 10. Photograph showing roadcut exposure of brachiopod coquina in Logana Member of Lexington Lime- stone ----------------------------------------------------------------------------------- 16 11. Photomicrograph of brachiopod coquina from the Logana Member ------------------------------- 16 12. Isopach map of the Logana Member of Lexington Limestone -----------------------------------­ 16 13. Photograph showing outcrop of Grier Limestone Member of Lexington Limestone ---------------­ 18 14. Photomicrographs of the Grier Limestone Member --------------------------------------------­ 21 15. Map showing distribution of subdivisions of Grier Limestone Member of Lexington Limestone ----­ 22 16. Photomicrograph of limestone from Grier Limestone Member showing bryozoan zooecia and crypto- crystalline carbonate-fluorapatite filling ______ ---------_________________ -------------------- 22 17. Map showing distribution of Perryville Limestone Member and Devils Hollow Member of Lexington Limestone ------------------------------------------------------------------------------- 25 18. Columna.r sections showing relation of Perryville Limestone Member to Tanglewood and Grier Lime- stone Members of Lexington Limestone ---------------------------------------------.------­ 26 19. Photograph showing outcrop of Faulconer Bed of Perryville Limestone Member -----------------­ 27 20. Photomicrograph of packed biomicrite from Faulconer· Bed of Perryville Limestone Member -----­ 27 21. Photograph showing quarry exposure of part of Perryville Limestone Member -------------------­ 27 22. Photomicrographs of the Salvisa Bed of the Perryville Limestone Member ---------------------- 29 23. Photographs showing exposures of Tanglewood Limestone Member of L·exington Limestone _______ _ 32 24. Photomicrographs of biosparites from the Tanglewood Limestone Member -----------------------­ 34 25. Isopach map of the Tanglewood Limestone Member of Lexington Limestone ----------------------­ 34 26-28. Photographs of Brannon Member of Lexington Limestone: 26. Roadcut exposure showing tilted block of calcarenite in upper part of Brannon Member __ 35 27. Outcrop showing characteristic interbedding of calcisiltite and shale --------------------- 35 28. Ball-and-pillow structure _________ ---________________________________________ -------- 36 29. Isopach map of Brannon Member of Lexington Limestone --------------------------------------­ 36 30. Photograph showing outcrop of Sulphur Well Member of Lexington Limestone ------------------­ 37 31. Map showing distribution of Sulphur Well Member, Stamping Ground Member, and Greendale Len- til of Lexington Limestone -----------------------------------------,---------------------­ 38 32. Photomicrograph of gastropod coquina from Devils Hollow Member ---------------------------­ 40 33. Photograph showing outcrop of Millersburg Member of Lexington Limestone -----------------­ 42 34. Photomicrographs of the Millersburg Member--------------------------------------------------­ 4:-l 35. Isopach map of Millersburg Member of Lexington Limestone -----------------------------------­ 43 36. Photograph s·howing contact of Lexington Limestone and Clays Ferry Formation ----------------­ 44 37. Photographs showing expoc::ures of the Clays Ferry Formation ---------------------------------­ 45 38. Isopach map of limestone facies in rocks of Lexington age in central Kentucky and adjacent parts of Ohio, Indiana, and Tennessee ------------------------------------------------------------- 56 TABLES Page TABLE 1. List of measured sections of the Lexington Limestone and related formations of central Kentucky-- 6 2. Chemical analyses of !Oamples of the Lexington Limestone and the Clays Ferry Formation -------- 8 3. Description of rock types of the Lexington Limestone and related formations ------------------- 52 \ LITHOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF THE LEXINGTON LIMESTONE (ORDOVICIAN) OF CENTRAL KENTUCKY By EARLE R. CRESSMAN ABSTRACT effect of the epifauna and flora. Transgression and regression of the rock types resulted fr?m varying rates of subsidence. The fossiliferous and bioclastic Lexington Limestone un­ During the time of deposition of the lower half of the derlies the inner Blue Grass region of central Kentucky. The Lexington Limestone, the sea floor sloped northward; cal­ formation is mostly of late Middle Ordovician age, but the carenite, formed above surf base in the south, grades suc­ upper part is equivalent to the basal beds of the type Cin­ cessively northward to fossiliferous limestone, nodular fos­ cinnatian Series (Late Ordovician) of southwestern Ohio. siliferous limestone and shale, and interbedded limestone and The Lexington rests disconformably on the Tyrone Lime­ shale. During deposition of the upper part of the Lexington, stone of Wilderness Age and is overlain conformably by in­ the southern part of the area subsided; calcarenite, deposited terbedded limestone and shale of the Clays Ferry Forma­ on a northwest-trending