REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH‐RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY

Abstract

Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high‐resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high‐resolution sclerochronology and a micro‐milled sampling strategy for δ 18 O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ 18 O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen isotope results, since δ 18 O shell appears to be strongly influenced by seasonal inputs of very low δ 18 O snowmelt‐water from adjacent coastal mountain ranges. The results show that shellfish were collected year‐round at this site over a 4000‐year period, and these data combined with other zooarchaeological lines of evidence support the interpretation of year‐round occupation.