Neotectonics and Taphonomy: Pleistocene Molluscan Shell Accumulations in the Northern Gulf of California

Abstract

Late Middle to early Late Pleistocene shallow marine deposits west of Bahia Adair, to the northern Gulf od California, have been exposed by tectonic uplift along the coast. Represented sedimentary environments include shallow subtital, tidal falt, tidal estuary, tidal channel and shoreface. The deposits contain a diverse molluscan fauna, often concentrated in shell beds. Based on taphonomic data, stratigraphic geometry and faunal composition, the shell beds are identified as beach berm accumualtions, tidal channel lags, subtidal community beds, or unconformity beds. While the first three types of shell beds form on many continental margins, the unconformity beds reflect the active tectonic setting of the northern Gulf of California