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Radiocarbon Variability in Crassostrea virginica Shells from the Chesapeake Bay, USA

Fifteen accelerator mass spectrometry (AMS) radiocarbon dates obtained on small subsections of archaeological and historical Crassostrea virginica (eastern oyster) shells provide a means to test for intrashell variability in 14C content in late Holocene Chesapeake Bay mollusks. Although salinity and temperature vary considerably throughout the year, the Chesapeake Bay generally lacks the strong coastal upwelling present in the eastern Pacific where intrashell 14C variability is significant. Intrashell variability in Chesapeake Bay C. virginica is between ∼60–100 14C yr, considerably smaller than the 120–530 14C yr ranges noted for shells from strong upwelling zones. As a precaution, we follow Culleton et al. (2006) and argue that large subsamples of shells across multiple growth increments are ideal for AMS 14C dating of mollusks to offset potential issues of intrashell 14C variability.