Stable Oxygen Isotope δ18O Analysis of Crocus Clam (Tridacna crocea) from Palau, Micronesia: Evaluating a Proxy for Sea-surface Temperature Reconstruction

Summary

For thousands of years and on a global scale, shellfish have been a key resource for peoples living in island and coastal environments. Not only were they critical food resources, but can act as records of paleoenvironmental conditions. In this study, we evaluated whether the crocus clam (Tridacna crocea) could satisfactorily record ambient water temperature via the incorporation of oxygen isotope ratios into the calcium carbonate matrix during shell growth. Modern Tridacna crocea were collected from intertidal zones near the prehistoric (ca. 3000-0 BP) site of Chelechol ra Orrak in the northern Rock Islands of Palau and compared with samples from the archaeological assemblage. The shells were sampled for stable oxygen isotope analysis, fractionation equations applied, and temperatures compared to modern reported nearshore temperatures to determine the efficacy of T. crocea’s temperature recording. X-ray diffraction was also used to determine the shell’s biomineralogical composition, necessary for selecting the appropriate water temperature conversion equation. Results demonstrate that this species is an accurate proxy for estimating ambient sea-surface temperatures (SST), particularly long-term changes due to its slower growth rate.

This Resource is Part of the Following Collections

• Insights from Increments: Advances in Geochemical and Microscopic Analyses of Hard Tissues   •
• Society for American Archaeology 82nd Annual Meeting, Vancouver, BC (2017)

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Record Identifiers

Abstract Id(s): 17270