High precision measurement of obsidian hydration layers on artifacts from the Hopewell site using secondary ion mass spectrometry

Obsidian hydration dating has served as one of the chronological indicators for the Hopewell Culture earthworks (ca. 200 B.C.-A.D. 500) in central Ohio. This work presents new obsidian hydration dates developed from high precision hydration layer depth profiling using secondary ion mass spectrometry (SIMS). These data suggest that long-distance exchange in obsidian occurred throughout the Hopewell period.