Assessment of past subsistence strategy and environmental impacts using novel geochemical analyses of mollusk shells

Summary

Archaeologists are beginning to apply two new analytical techniques to estuarine mollusk shells: inferring paleo-salinity from sclerochronological oxygen isotope profiles and assessing anthropogenic waste loading from mollusk nitrogen isotope measurements. These related approaches may offer insight into subsistence priorities and environmental alteration, but data from each should be interpreted with caution until these proxies are more completely validated. Potential uses and limitations of these methods will be discussed. For example, absolute values of oxygen isotope profiles in American oyster (Crassostrea virginica) and quahog clam (Mercenaria spp.) reflect the average salinity of the shellfish’s habitat, permitting estimates of the relative distance people travelled to collect. However, coastal hydrology changes over time, and salinity gradients are geographically variable, so detailed reconstruction of collection location is not possible. Similarly, nitrogen isotopes measured in the shells of the same species may trend across salinity gradients, which could corroborate oxygen isotope salinity analysis. However, shell nitrogen isotope values also reflect anthropogenic N loading. Deconvoluting the influences of salinity and anthropogenic pollution could create useful proxies for both parameters, but may be difficult to accomplish in areas where environmental variation is subtle or site formation processes are complex.

This Resource is Part of the Following Collections

• Society for American Archaeology 81st Annual Meeting, Orlando, FL (2016)   •
• Recent Considerations of Coastal Subsistence Practices in the Southeastern USA

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