Assessing Habitats of Mollusk Collection and Models of Late Archaic Settlement along the Atlantic Coast, USA using Oxygen Isotope Sclerochronology

Oxygen isotope analysis was performed on Mercenaria and Crassostrea virginica from the Sapelo Island Shell Ring. This study is based on the observation that temperatures are similar in all of the habitats surrounding the island, but the δ¹⁸O_water trends across the habitats co-vary with salinity. Accordingly, the shells grown in these habitats contain sinusoidal oscillations in δ¹⁸O through ontogeny due primarily to seasonal temperature variation, but the absolute values reflect the salinity ranges of each habitat. Assuming a constant oxygen isotope/salinity gradient since the time of site occupation, it appears that both of these mollusks were exploited over nearly the full range of their salinity tolerances. While precise estimate of distance to collection cannot be made, these data suggest that mollusks were harvested at considerable distances from the site. In addition to providing insight into past subsistence strategies, this research establishes a new method of assessing catchments area and mobility practices.