IDENTIFYING ENVIRONMENTAL CONDITIONS OF THE MIDDLE DEVONIAN BIOSTROME AT THE FALLS OF THE OHIO (CLARKSVILLE, INDIANA) THROUGH EXAMINATION OF CORALLUM CURVATURE IN RUGOSE CORALS

The Falls of the Ohio State Park, in Clarksville, Indiana, is a well-preserved and well-exposed fossil biostrome from the middle Devonian. The coral zone layer of Jeffersonville Limestone, consists of an upper coral zone and a lower coral zone. Together, these zones contribute the highest concentration of fossils in the Jeffersonville Formation. In the fall of 2017, a total of 2,298 fossils were examined along 81 meters of transect, specifically from the extensive exposures of the Upper Coral Zone. The data includes genus-level identification, photography and measurements of size, shape, and compass bearing. The fauna consisted of both colonial and solitary rugose corals, tabulate corals and stromatoporoid sponges. Rugose corals made up the majority of the data, accounting for 61% of the fossils analyzed. As rugose corals grow, septa are added in the direction of growth. The size and direction of each septa correlates to the environmental conditions the coral experiences, sometimes resulting in bending if the position of the rugose coral was disturbed. Previous research on rugose corals demonstrate that the curvature of a rugose corallum is largely dependent on the water energy in the environment, local substrate conditions and size, primarily width, of the coral.

The goal of this new phase of research is to assess the amount of curvature within and among genera in the coral zone. In addition to the assessment of coral size and shape observed along transects in the previous field study, a new set of measurements of bending rugose corals will be gathered using 1m² quadrat sampling of the fossil beds. By using square quadrats rather than linear transects, a much larger area of the fossil bed can be examined, thus increasing the likelihood of encountering instances of bending in rugose corals. Ultimately, through the analysis of the difference in size, shape and distribution of bending rugose corals it may be possible to generate more accurate estimates of water energy in the Upper Coral Zone of the Falls of the Ohio.