A Late Pleistocene to Holocene Record of Precipitation Reflected in Margaritifera falcata Shell δ18O From Three Archaeological Sites in the Lower Salmon River Canyon, Idaho

Abstract

Oxygen-18 (δ18O) concentrations in Margaritifera falcata shells preserved in three archaeological sites in the Lower Salmon River Canyon of Idaho are compared with modern mussel shells. Shell δ18O records show that Late Pleistocene and Early Holocene climates were drier with occasional periods of increased precipitation. After c.4000 years bp, precipitation is higher in the Salmon River basin than at present and trends toward modern conditions after c.1800 years bp. The climatic conditions reflected by fluctuations in shell δ18O are matched by regional palaeoenvironmental records, including pollen, glacial and palaeohydraulic proxy sources, and are compared with major changes in Plateau prehistoric cultural patterns. Studies of late Quaternary records of freshwater bivalve shell δ18O are useful for reconstructing climatic conditions and complement geoarchaeological studies in riparian contexts.