Crescent Hill Chert: A Geological and Cultural Study of a Raw Material Procurement Area in Yellowstone National Park, Wyoming
In 2009/2010 the Montana Yellowstone Archaeological Project (MYAP) conducted survey of the Crescent Hill chert outcrop (site 48YE729) in the northern portion of Yellowstone National Park. Occurring in a variety of colors and qualities, the chert precipitated within the Eocene-era Crescent Hill basalt formation. The procurement area encompasses 2,124.8 acres, with nine surface outcrops, five of which were clearly utilized by Native Americans during prehistory. With the materials previously being uncharacterized, hand samples representative of the outcrop areas were collected and analyzed using macroscopic, petrographic, and geochemical techniques. In doing this, the provenance of artifacts found in archaeological assemblages can be traced back to their original source outcrop area. Results show that the material is highly variable in appearance and elementally scattered, making it hard to differentiate Crescent Hill from other regional cherts. However, detailed macroscopic analysis provides an avenue for artifacts to be matched to hand samples from the source area. In doing this, elucidations regarding hunter-gatherer lithic technological organization and land-use can be made. Two archaeological sites in the lowest and driest portion of Yellowstone National Park, the Yellowstone Bank Cache Site (24YE355) and the Airport Rings Site (24YE357), show a heavy reliance on Crescent Hill chert (CHC). At both sites, CHC represents the second most abundant raw material type found in archaeological assemblages, next to Obsidian Cliff obsidian. Lithic raw materials from both source areas within well-dated hearth contexts indicate a temporal change in use of the materials from the Late Archaic to the Late Prehistoric periods, likely due to changes in human use of the landscape. Additionally, utilization of the two materials shows that prehistoric hunter-gatherers may have favored an embedded approach in obtaining materials from Crescent Hill, as opposed to Obsidian Cliff, representing a highly homogeneous isotropic source using a more direct approach of procurement. An examination of variables, including quality, abundance, distribution, and mode of occurrence of lithic raw material on the landscape were used to evaluate each procurement area. As reflected in a gravity model (Wilson 2007), Obsidian Cliff is superior in geological quality and ubiquitously found across the landscape in cultural contexts, making it the more desirable of the two sources.
archaeology, chert, lithic technological organization, Yellowstone National Park
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