Origin and paleoecology of Maastrichtian rockground and chalk facies in southcentral Alabama

Abstract

A phosphatic rocky substrate (rockground) of Maastrichtian age has been recognized at the top of the Ripley Formation in southcentral Alabama, near the town of Braggs. The rockground is developed in a coarse-grained sandstone and is associated with a regional unconformity and probable subaerial exposure (68 Ma sequence boundary). The sandstone was subject to high-energy conditions which produced large, well-rounded cobbles. Thus, at some point, the surface was presumably a rocky shore. The rockground later hosted a low diversity epibiont fauna of bivalves, bryozoans, and serpulid worms