The antiquity of Olivella shell beads at CA-ORA-64: AMS radiocarbon dated between 9420 and 7780 cal BP

Abstract Investigations in the 1960s and 1970s showed the Irvine site (CA-ORA-64) to be among the oldest shell middens known from the Pacific Coast of North America. The site chronology, based on conventional analysis of mixed shell samples collected from heavily bioturbated soils, extended back to ca. 8440 RYBP. Recent work at the site provided an opportunity to refine the CA-ORA-64 chronology via AMS 14 C dating of single shell fragments, including 14 Olivella beads. Long considered to be one of the earliest ornament types made by Pacific Coast peoples, such spire-removed Olivella beads were used through much of the Holocene and generally are not good chronological indicators. AMS analysis of the CA-ORA-64 specimens, however, produced a consistent series of Early Holocene dates that includes some of the oldest securely dated shell beads in North America. Along with obsidian from interior sources, Olivella beads played an important role in early exchange networks between coastal and interior peoples. Methodologically, our research demonstrates the utility of AMS 14 C dating in determining the age of key artifact types found in multicomponent sites with assemblages affected by stratigraphic mixing.