TAPHONOMIC TRENDS IN LATE CENOZOIC BENTHIC MOLLUSKS FROM MID-ATLANTIC COASTAL PLAIN DEPOSITS

The Coastal Plain deposits of the Eastern U.S. are mostly or entirely unlithified, containing well-preserved macro-invertebrate fossils, and present a unique opportunity for bulk-sampling and paleoecological analysis. However, even with these well- preserved deposits, taphonomic biases may overprint spatial and temporal aspects of the fossil record, and should be evaluated quantitatively prior to undertaking any paleobiological analyses. The taphonomic trends throughout the Late Cenozoic fossil record have not been quantified for any region of the world and their potential biasing importance is therefore not understood.

This study assesses taphonomic trends in the Late Cenozoic Coastal Plain deposits by using specimen-based taphonomic scores. These scores are subjected to multivariate methods to quantify the scale and nature of taphonomic changes in this mollusk-dominated fossil record and evaluate for presence of spatial and/or temporal taphonomic biases.

Bulk samples from the mid-Atlantic Coastal Plain of Maryland, Virginia, and adjacent areas, comprising >100 samples and >50,000 specimens were used for this study. Samples are all Middle to Late Cenozoic in age, and were collected in bulk and subsequently sieved and identified. Veneroid and pectin bivalves were selected for taphonomic analysis since they are common throughout the intervals selected for study, and also robust enough to be identified even when poorly preserved. A series of taphonomic variables quantifying physical, chemical, and biological aspects of shell alteration were recorded for each veneroid bivalve specimen. These data will be subjected to multivariate analysis in order to quantify large-scale spatial and temporal taphonomic patterns in the Late Cenozoic fossil record of the mid-Atlantic Coastal Plain.