PROVENANCE STUDY OF PREHISTORIC OBSIDIAN ARTIFACTS FROM THE MANN SITE IN POSEY COUNTY, INDIANA AND THEIR ARCHAEOLOGICAL SIGNIFICANCE

The geological sources of lithic artifacts help to reconstruct exchange patterns and trade routes of prehistoric cultures. Obsidian sourcing, in particular, is especially reliable because source outcrops are typically homogenous and occur in limited geographic regions. Five obsidian blades recovered from a Prehistoric Hopewell Site known as the Mann Site in Posey County, Indiana were analyzed by non-destructive x-ray fluorescence for this study. The Hopewell culture flourished in Southern Indiana during the Middle Woodland Period (200 B.C to A.D. 500). Prehistoric obsidian artifacts recovered from Southern Indiana archaeological sites are noteworthy, given that the nearest known obsidian source is over 1600km (1000 miles) away.

The trace element characteristics, specifically Sr versus Zr, confirmed the source for four of the five Mann Site artifacts as the Bear Gulch, Idaho obsidian source. One obsidian blade originated from Obsidian Cliff, now in Yellowstone National Park, Wyoming. Two other artifacts, known to originate from the Yellowstone Plateau, showed trace element signatures representing the Obsidian Cliff source. For comparison, two fine-grained volcanic lithic artifacts from West Virginia with distinctly different trace element characteristics originate from a geologic source yet to be determined.

Identifying the geologic source of obsidian artifacts from the Mann Site confirms that, like other Hopewell cultures in the Midwest during the Middle Woodland Period, inhabitants of the Mann Site either obtained obsidian through trade or by traveling to Obsidian Cliff in Yellowstone National Park, Wyoming and Bear Gulch, Idaho.