Conodont biostratigraphy and paleoecology of the Upper Ordovician Miamitown Shale in the Cincinnati region, Ohio

Abstract

In order to study the conodont plaeoecology, biostratigraphy, and depositional environment of the Miamitown Shale, 11 samples were collected from three localities near Miamitown. All samples were productive and yielded well preserved conodonts. The relative frequency of Amorphognathus, Icriodella, Phragmodus, and Plectodina indicate a progressive deepening of the depositional environment from the uppermost Fairview Formation. The presence of elements of A. superbus in the lower Miamitown shows that the top of the A. superbus zone is stratigraphically higher than has been assumed previously in the literature. Apparently this key stratigraphic level is in the upper Miamitown or higher, which necessitates a revision of the regional correlation of this portion of the Cincinnatian Series, the reference sequence of the North American Upper Ordovician.