Taphonomic Signature of Shell Accumulations in Cores: An Indicator of Depositional Environments in Holocene Nearshore Sediments, West-Central Florida

Abstract

ABSTRACT Vibracores taken along the barrier island coastline of west central Florida display distinct lithofacies characterized by unique taphonomic signatures. High energy lithofacies are composed principally of shell beds, which can be classified into wave- and current-generated. Wave-generated shell accumulations can be divided into pulse-type and agitated-type. Current accumulations can be divided into thin-type (formed under weak, episodic currents), and thick-type (formed under stronger, more continuous currents). Pulse-type shell beds are characterized by random orientation, high fragmentation, poor rounding of shell fragments, moderate shell density, poor sorting, and moderate lateral extent. Agitated-type are characterized by random and con-cave-up orientation, very poor rounding, great thickness, moderate to high fragmentation, high density, and variable lateral extent. Thin-type are characterized by concave-down orientation, poor rounding, very low thickness, very high fragmentation, lower density, moderate sorting, and moderate extent. Thick-type are characterized by concave-down orientation, poor rounding, moderate thickness, moderate fragmentation, high density, good sorting and local lateral extent. This study illustrates the utility of studying shell beds in cores, as a distinct component of the Holocene stratigraphic column. Results indicate that the character of shell beds in the study area is due to some combination of magnitude and duration of wave and current energy and coastal morphology.