Journal of California and Great Basin Anthropology

Northern Utah and southern Idaho have numerous sources of obsidian (e.g., Browns Bench, American Falls, Malad, and Wildcat Hills). This article describes a replicable technique for creating regional obsidian hydration chronologies and applies it to prehistoric artifacts recovered during data recovery along the Ruby Pipeline route, which extends eastwest across northern Utah. The method uses regionally-sampled hydration thicknesses to determine a source-specific quadratic equation that is separate from any project-specific data. The estimated hydration rate strongly agrees with radiocarbon and optically stimulated luminescence dates from excavations as well as with common projectile point typologies. The hydration rates, when applied to data from northern Utah, suggest that persistent occupation occurred in the area during the Early Archaic at roughly 8,400 cal B.P.