TAPHONOMY OF MIOCENE CETACEAN VERTEBRAE FROM CARMEL CHURCH QUARRY, VIRGINIA

Carmel Church Quarry (CCQ), a granite quarry in Caroline County, Virginia, exposes five Tertiary formations within a 10 m thick section, which includes the Calvert Formation. Published research on this site is limited and much of it involves systematic descriptions of organisms that have been found. The research presented here will contribute to the understanding of cetacean taphonomy and the depositional environment at this site and will allow the comparison of more western, near-shore Calvert deposits with more common eastern exposures. In order to evaluate the taphonomy of the cetacean material from the Calvert Formation at CCQ, we examined 288 prepared vertebrae housed at the Virginia Museum of Natural History. This study focuses specifically on determining whether preferential preservation occurred among the four sections of the cetacean vertebral column (cervical, thoracic, lumbar, and caudal) and determining whether the paleoenvironment influenced the preservation of the vertebrae.

The vertebrae were measured for size (volume of centrum) and several anatomical and preservational observations were recorded: part of the vertebral column to which each belongs; whether it was found isolated, associated, or articulated with other vertebrae; preservation state on a scale of 1 (pristine) to 4 (heavily abraded); the presence of borings and epiphyses; and whether it is classified within the suborder Mysticeti or Odontoceti. Preliminary results suggest that articulated and associated vertebrae are better preserved than isolated vertebrae. Vertebrae found in more pristine conditions came from adult (both epiphyses present) cetaceans. Preliminary results also indicate that there are no biases in the preservation likelihood according to vertebral region, with the exception of the axes, which are over-represented relative to axes within the sample collection. Comparison of centrum size across preservation states indicates that larger vertebrae tend to be better preserved (F₂₆₄=9.74, p <0.0001). We also documented a negative correlation between articulation and preservation. More articulated vertebrae tended to be better preserved (R₂₈₈=-0.448, p<0.0001).