During the Middle Devonian (385 mya), the Kaskaskia Sea was transgressing over what is now eastern North America. Many biostromes, which are layers of densely-packed fossils, have been studied within this region, including those at the Falls of the Ohio State Park in Clarksville, Indiana. These fossil beds include the laterally-extensive Coral Zone of the Jeffersonville Limestone, composed of rugose and tabulate corals and stromatoporoid sponges. The Coral Zone contains few organisms besides these biostrome builders. In order to compare the Falls of the Ohio with similar ecosystems throughout the Kaskaskia, a database of like-environment fossil localities from the middle Devonian was assembled using the Paleobiology Database and literature review. Paleomaps of the geographic range of each of the most abundant taxa were generated using the Paleobiology Database by mapping the latitude and longitude paleocoordinates of fossil occurrences. For each locality considered, the paleoenvironmental parameters (e.g., water depth, energy, and substrate), taxonomic diversity, and categories of organismal interactions were also noted. Through the generation of maps in combination with an assessment of paleoenvironmental conditions, the geographic ranges and environmental tolerances of some of the most common biostrome-building organisms were analyzed across regional and global scales.
Results/Conclusions
The majority of the western Kaskaskia Sea contained similar organisms to the Falls of the Ohio. The biostrome communities in the eastern portion of the Kaskaskia exhibited higher levels of taxonomic diversity, revealing a general diversity gradient across the seaway, with an increase in diversity from west to east. Favosites exhibited the greatest geographic distribution while Prismatophyllum was the most geographically restricted genus considered in this study. Heliophyllum, was the most abundant coral genus at the Falls of the Ohio and occurred in abundances twice as frequent as Favosites. However, when considered on a global scale, Heliophyllum exhibited a smaller geographic range. Through analyses of abundance distributions and geographic ranges, it may be possible to understand how biostrome builders vary through space according to the regional and global paleoenvironmental parameters of the Middle Devonian, thereby adding to our understanding of these ancient paleocommunities.