PALEOECOLOGY OF THE LATE CARBONIFEROUS HUGHES CREEK SHALE, SOUTHEASTERN NEBRASKA

The Late Carboniferous (~290 million years) Hughes Creek Shale of the Foraker Formation is exposed discontinuously throughout the Forest City Basin of the North American Mid-Continent. While outcrops are extensive in Kansas, surface exposures in Nebraska occur only in the extreme southeastern corner of the state as shales and minor limestone. A measured stratigraphic section (~2m) near the town of Falls City, in Richardson County, Nebraska, contains a diverse and abundant macrofauna dominated by: brachiopods, bryozoans, crinoids, rugose corals and trilobites. Taphonomic analysis of the fossils (size-frequency distribution, articulation ratio, pedicle/brachial valve ratio, corrasion, epibiont coverage and fracture type) provides support for a hypothesis of short seafloor residence times for skeletal remains. While biased somewhat by preservation condition, taphonomic analysis strongly suggests that the fauna represents a single paleocommunity, amenable to paleoecologic analysis. Diversity indices (simple species richness, Margalef, Shannon-Weiner, equitability) were calculated by the PAST software program and compared with coeval paleocommunities in the Illinois and West Texas Basins. Finally, we document the first Nebraska – Hughes Creek Shale occurrence of the shell-crushing shark, Petalodus ohioensis, the top-level carnivore for this basin.