DEVONIAN STROMATOPOROID ASSOCIATIONS AT THE FALLS OF THE OHIO STATE PARK, CLARKSVILLE, INDIANA

Stromatoporoids are calcitic sponges that occurred in the fossil record from the Early Ordovician to Late Devonian period. These sponges show evidence of interaction with other organisms, especially rugose and tabulate corals. Some corals appear to benefit from the rigidity of stromatoporoids in response to turbulent marine conditions. Stromatoporoids and many corals went extinct during the Frasnian-Famennian crisis when paleoenvironmental parameters were shifting. For this reason, studying the paleoecology of these taxa may provide insight to specific environmental conditions during this critical interval of geologic time. Additionally, detailed studies of stromatoporoids may also reveal more about the nature of the relationships they had with other taxa, such as endosymbiotic coral.

This research was performed at the Falls of the Ohio in the Coral Zone of the Jeffersonville Limestone, a biostrome of exposed Devonian-age fossils located in Clarksville, Indiana. Even though this is an important paleontological site that contains several hundred species of coral, no peer-reviewed paleoecological studies have been conducted here in more than fifty years. Organisms in the coral zone were studied using transect sampling along a portion of the bedding plane. Each fossil along the 81 meters of transect line was identified, measured, and if the fossil was elongate, a compass bearing was recorded. The data were then entered in Excel and analyzed. Stromatoporoids accounted for 72.9% of biomass of fossils identified, demonstrating their overwhelming dominance and importance in the biostrome. A meta-analysis using scientific literature and the online Paleobiology Database was also performed to compare results from the Falls of the Ohio to other Devonian systems across the world. Through identifying and evaluating stromatoporoid-coral interactions, the ultimate goal of this research is to gain a greater understanding of why stromatoporoids were vulnerable to extinction at the end of the Devonian period.