ISOTOPE STRATIGRAPHY OF THE VISÉAN CARBONATES IN THE ST. LOUIS AND STE. GENEVIEVE MEMBERS OF THE SLADE FORMATION IN SOUTHEAST KENTUCKY

This research comprises measured sections and whole rock analysis for Viséan carbonates that comprise the St. Louis and Ste. Genevieve Members of the Slade Formation in samples from caves and outcrop along the margin of the Cumberland Plateau in Southeast Kentucky. The samples span 46 meters in increments of 30.5 cm from three locations: the entrance to Grayson Gunnar Cave, Bridgeman Mountain, and Redmond Creek Cave, all in the Otter Creek watershed. Prepared measured sections include details on bedding, fabric, and fossil assemblage. Whole rock powders were prepared using a carbide bit on a Drimmel tool. A split of the powder was analyzed for d¹³C and d¹⁸O using a Kiel device on a Thermo-Finnigan MAT 253 at the KPESIL (University of Kansas). A second split of powder was analyzed on a Rigaku MiniFlex XRD (Ball State University) for weight fractions of calcite, dolomite, and silica.

A detailed stratigraphic column accompanies this research and includes correlations among the sites tuned to the isotope and mineralogical data. d¹³C values range between -1.2‰ and 4.7‰ and d¹⁸O values range between -8.8‰ and 2.4‰ with a trend toward more negative values higher in the section. The Ste. Genevieve member is relatively pure calcite with occasional chert. In contrast, the St. Louis member is comprised of several dolomitic and silica rich zones. d¹⁸O values are enriched in the heavier isotope in these dolomitic zones, by as much as +6‰, suggesting a strong connection to isotopic alternation during burial diagenesis and dolomitizaton. d¹³C values are depleted in the heavier isotope adjacent to lag surface indicated in the field by algal laminates, breccia, and paleosol and associated with the boundaries of depositional cycles that are 2-3 meters in scale.