BURIED ALIVE AND DEAD: USING ICHNOLOGIC, PALEOECOLOGIC AND TAPHONOMIC DATA FROM FOSSIL BIVALVE SHELLS TO RECONSTRUCT PALEOENVIRONMENTS

An organism's hard skeletal remains can contain data about its life, death and post-mortem history, all of which can be used in reconstructing paleoenvironmental conditions experienced by the living organism and its dead remains. The paleoecologic preferences of the organism are frequently the most valuable data when reconstructing past environments, but taphonomic and ichnologic analyses can also yield useful information, especially when comparing specimens of the same species from different paleoenvironmental settings.

Some variables (e.g., shell size and relative abundance) are primarily controlled by environmental and ecological conditions experienced by living organisms. Features like predatory gastropod drill holes and pre-mortem epibiont infestations result from the interactions of living species. Other epibiont infestations, shell borings and further taphonomic processes provide data about both the depositional environment and other species that lived within the paleocommunity.

Three species of marine bivalves, Anadara transversa (Arcidae), Carditamera floridana (Carditidae) and Chione elevata (Veneridae), were found in all samples from an outcrop of the Pleistocene Fort Thompson and Bermont Formations in Florida. The two formations contained similar faunal assemblages but were deposited under somewhat different shallow marine paleoenvironmental conditions. The three species produced roughly similar sized, robust shells, making them good candidates for comparative analyses both within and between species. We found differences within and between the three species from the two paleoenvironments in relative abundance, shell size, predatory gastropod boring frequency, presence of epibionts and post-mortem taphonomic alteration.