SEDIMENTOLOGICAL, PALEONTOLOGICAL, AND TAPHONOMIC ANALYSES OF A FOSSILIFEROUS SHALLOW MARINE K-PG EVENT BED NEAR FORT DEPOSIT, ALABAMA, USA

Approximately 66 million years ago, the Chicxulub Impactor collided with Earth marking the end of the Cretaceous. The collision had a massive impact on the environment and life on the planet. This impact was followed by seismic activity and a series of tsunamis. Evidence of the Cretaceous-Paleogene boundary (K-Pg) can be observed along the Gulf Coastal Plain in a new locality near Fort Deposit, Alabama. Two different formations are exposed: the uppermost Maastrichtian Prairie Bluff Chalk (PBC) and the overlaying lowermost Danian basal Clayton Formation. The transition from the PBC to the Clayton Fm is separated by a sharp contact. The PBC is composed of a fine-grained sand to silty marl. The basal Clayton Fm consists of an extremely fossiliferous (coquina-like), siliciclastic rich bed composed of a coarse-grained quartz sand matrix, impact spherules, along with multiple PBC rip-ups, and no evidence of bioturbation. This may be representative of a high energy, rapid depositional event (e.g., tsunami). Species richness and Simpson’s Index (D) were calculated for the event bed. Preliminary results indicate an extremely diverse and rich fauna (Simpson’s = 0.87, species richness = 33). Fauna from the PBC differs markedly from the event bed. Fauna within the event bed (e.g., Glycymeris rotundata and Trachycardium) have not been observed in the PBC below and are likely allochthonous. Event bed fossils are preserved as randomly oriented, calcite- and clay-replaced shells, with a lithologically diverse infill. Specimen infill includes PBC matrix (reworked), some with spherules and quartz sand, while others are empty suggesting a quick burial related to a high energy event. Thus, the change in sediment size, increased of siliciclastics, high biodiversity, random fossil orientation, lack of bioturbation, and varied matrix infill are strong indicators of a hydrodynamic accumulation resulting from a tsunami deposit that took place subsequent to the Chicxulub Impactor.