EFFECTS OF PREHISTORIC COOKING METHODS ON δ15N IN MOLLUSK SHELLS

Geochemical analysis of mollusk shells from archaeological sites is a useful means of acquiring paleoenvironmental data. Recently, nitrogen isotopes have been identified as a potential new proxy in these shells. δ¹⁵N in mollusk shells is affected by numerous anthropogenic and natural influences including fertilizer pollution, trophic pyramid disruption, and productivity variation, and may be used as an environmental proxy for these conditions. However, little is known of the effects of pre-depositional treatment such as cooking on δ¹⁵N in the shell matrix. In this study, fourteen Crassostrea virginica oysters and twelve Mercenaria spp. clams were treated using five different cooking methods to determine if N concentrations and/or δ¹⁵N values were impacted. One valve from each shell was cut symmetrically across growth bands with one half cooked and the remaining half untreated as an experimental control. Post-depositional alteration may have also affected nitrogen concentrations and δ¹⁵N values in archaeological shells. %N and δ¹⁵N were compared in modern, museum archived, and archaeological shells from the same region to assess alteration.