STORM DOMINATED SEDIMENTATION IN THE AUSTIN CHALK, WACO, TEXAS, USA

Marsupites testudinarius is a well known index fossil of the Late Cretaceous, whose last appearance defines the base of the Campanian stage. A section of Waco Creek exposes a section of the Austin Chalk, which contains a mass death assemblage of Marsupites in distinctly cross-bedded layers. Underlying beds start abruptly and are dominated by large-scale ripple structures, while the beds overlying individual Marsupites deposits are finely laminated. Inclusion of angular mud clasts, shattered and imbricated shells, as well as the mass-death assemblage of cross-bedded Marsupites is indicative of strong turbidity and reworking of sediments within the Austin Chalk. While sharing some similarities with Bouma sequences, the section suggest the structures observed are storm produced.