ANALYSIS OF CHONDRICTHYAN REMAINS FROM THE PENNSYLVANIAN UPPER BRUSH CREEK LIMESTONE, LOWER BRUSH CREEK LIMESTONE, PORTERSVILLE SHALE, AND AMES LIMESTONE OF ATHENS COUNTY, OHIO

Dermal denticles, isolated teeth, and other microscopic remains were used to identify chondrichthyan species found in Pennsylvanian age marine sediments of the Conemaugh Group in Athens and Guernsey County, Ohio. This study is an extension of work done by others, specifically Michael Hansen (1986), who performed an analysis of microscopic chondrichthyan remains in Ohio, including Athens and Guernsey County. During the course of the study, several of the localities sampled by Hansen were revisited, many of which have not been investigated in nearly forty years, while many new localities were located, sampled and analyzed.

All localities were analyzed using modern techniques, including; GPS, GIS, and high resolution digital photography. Additionally, hand samples, thin sections, and stratigraphic columns were prepared from samples and data collected at each location. Carbonate samples were dissolved in buffered acetic acid to release phosphatic chondrichthyan material. Siliciclastic material was broken down using an aqueous solution of sodium bicarbonate. The isolated remains were counted and identified to the species level when possible.

The identified chondrichthyan faunas from the Late Pennsylvanian rocks of Athens and Guernsey Counties were compared to those found in similar age rocks in the Mid-Continent. With few exceptions, the chondrichthyan fauna that was found within this limited portion of the Appalachian Basin, did not match those found in previous examinations of Pennsylvanian strata within the Mid-Continent. Furthermore, a comparison of the genera found in the two paleoenvironments resulted in a Sorensen’s Similarity Index value of 0.33. The differences in beta diversity may be primarily due to the vastly different paleoenvironments of the two regions. The Appalachian Basin was a shallow, well oxygenated, stable near shore environment, whereas the Mid-continent was deep, with stratified oxygen, temperature, salinity, and photic zones creating a highly variable environment.