Stable Isotope Provenance Analysis of Olivella Shell Beads From the Los Angeles Basin and San Nicolas Island

ABSTRACT

Production of marine shell beads in island and coastal settings was an important activity in prehistory, with important political and economic ties. Currently, there are few methods to track beads to their locus of production. Examining the spatial distribution of bead types provides one method of doing so. Chemical and stable isotopic methods provide an additional and independent means of testing hypotheses generated by spatial distributions. We use stable oxygen, carbon, and strontium isotope data to reconstruct provenance zones for 18 Olivella biplicata beads from the Los Angeles Basin and San Nicolas Island, California. We compare the results to isotopic data from modern and radiocarbon-dated whole shells collected along the Pacific Coast. Results indicate that all 18 beads were manufactured from shells growing in open coast locations south of Point Conception. Differences in isotopic composition between bead types suggest that not all were produced in the same location. Some, such as callus beads (K1), have highly variable composition, suggesting production in a range of locations. Others, such as thin lipped (E1), seem to have been produced in more restricted regions.

Keywords:

• Southern California
• bead production
• Olivella biplicata

ACKNOWLEDGEMENTS

Funding for this research was provided through grants from the Wenner Gren Foundation (#6977) and the National Science Foundation (BCS-0504615) to JWE and HJS. We thank Joel Commisso, David Winter, and Greg Herbert for assistance in the isotope analyses, Laura Brink, Rowan Gard, and Pamela Reynolds for help in preparing and drilling shell samples, Doug Kennett, Michael Glassow, Linda Hylkema, Randy Milliken, Dustin McKenzie, Allika Ruby, and Randy Wiberg for collecting and/or making shell samples available for analysis, two anonymous reviewers for useful comments, and Angela Kellar, Seetha Reddy, Statistical Research, Inc. for making bead samples available for analysis. Finally, we kindly thank the Shore Stations Program and University of California, San Diego for hosting and supplying modern SST and salinity data.