A novel application of sclerochronology: Assessing the paleoenvironment of a marine transgressed Archaic Period archaeological site in the Gulf of Mexico

Abstract

Sequential oxygen (δ18O) and carbon (δ13C) isotope analysis were performed on eight eastern oyster (Crassostrea virginica) valves excavated from a marine transgressed archaeological site on the southwest coast of Florida, USA. The oysters were attached to Archaic Period human skeletal material and serve as a marker of mid-Holocene sea level rise at this once-inland mortuary pond. Data were analyzed to— (1) determine if a sample of oysters excavated from the site represent one or more inundation episodes, (2) assess past water parameters as the pond was transgressed, and (3) determine how long the oysters grew on exposed human skeletal material. Results of sclerochronological analysis and radiocarbon dating demonstrate there were two distinct environments at the time of oyster growth, each representing separate time periods and water parameters, with the earlier oyster group indicating fresher water parameters. Oysters were between one and three years old, suggesting human skeletal material was exposed for at least that long. This is the first instance in which oysters attached to Archaic Period skeletal material were used to draw wider conclusions about past marine transgression and environmental change, and results show that oysters contain valuable information for investigation at drowned archaeological sites. This research clarified methodologies that could be employed to better understand sea level rise's effects on archaeological sites on drowned portions of continental shelves.