14-1 Preliminary Report on Conodont Biostratigraphy of the Silurian Estill Shale at Measley Ridge in Southern Ohio

Abstract:

The Subcommission on Silurian Stratigraphy is currently re-evaluating the base Wenlock Global Boundary Stratotype Section and Point (GSSP) and is looking for new candidates for this golden spike. In addition, they are also looking for Standard Auxiliary Boundary Statotypes (SABSs) to supplement the GSSP and improve regional correlation. The Measley Ridge roadcut in southern Ohio is a potential candidate for a SABS for the base of the Wenlock Series.

The upper Estill Shale Formation at Measley Ridge in Adams County, Ohio preserves conodonts from the Ireviken Extinction Event. The Measley Ridge roadcut is located along Ohio State Route 32 in Adams County and is positioned on the Cincinnati Arch. The Estill Shale is composed of calcareous shales ranging from massive towards the base and grading into fissile, silty shale towards the top. The Estill Shale is unconformably overlain by the Bisher Formation. Bulk rock samples for this study were collected at approximately every 15-30 cm through the upper 11.75 m of the Estill Shale. The conodont species represented in this section are Pterospathodus amorphognathoides amorphognathoides, Pseudooneotodus bicornis, Ps. tricornis, Distomodus staurognathoides, Ozarkadina excavata, and Panderodus sp. The most abundant species throughout the Estill Shale is Pt. amorphognathoides amorphognathoides with a wide range of element types being represented.

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