Journal of California and Great Basin Anthropology

Energy dispersive x-ray fluorescence (EDXRF) analysis of geological obsidian samples from three localities in the southern Birch Creek drainage revealed that the vast majority of nodules represent the Walcott Tuff, a widespread toolstone-caliber volcanic glass in eastern Idaho. XRF data generated from analysis of over 500 obsidian artifacts from four archaeological sites in the Birch Creek Valley document the reliance of prehistoric peoples on Walcott Tuff obsidian. Data from newly documented Walcott Tuff exposures lead us to conclude that people who frequented the Birch Creek Valley could have acquired obsidian from proximate Walcott Tuff exposures without having to travel over 100 km. south to the American Falls area. These results underscore the importance of documenting, and geochemically analyzing, locations of artifact-quality ash-flow tuff obsidians prior to advancing archaeological conclusions about obsidian conveyance and population mobility.