Community replacement of a Pleistocene Crepidula biostrome

A sequence of fossil associations preserved in early Pleistocene mudstone, exposed on the Neuse River, eastern North Carolina, illustrates community replacement by species turnover, in this case involving addition of new species with rank demotions of formerly important community members. Here, a Crepidula biostrome is replaced by more diverse fossil associations dominated by oysters and infaunal bivalves. Biostrome deposits represent an extensive Crepidula snail bank that occupied a subtropical bay environment with low turbidity, near-normal marine salinity, and temporally stable water currents and food supplies. Because of local shoaling, extensive substrate coverage by these sessile epifaunal gastropods was gradually disrupted. A patchier subtidal environment, with more varied habitats for benthic organisms, succeeded the snail bank, thus giving rise to species-rich Oslrea clump and Anadara-Noetia associations containing only a few remaining Crepidula aggregations. Community replacement, species turnover, addition with rank demotions, autochthonous fossils, subtropical marine bay.