摘要：Testing of a bison bone deposit at the base of a 25m sandstone cliff at the Certain site, 34BK46, western Oklahoma, yielded resharpening flakes and a butchering tool. These artifacts, plus the density of bison remains suggest this cliff was used as a bison jump. Bone from this deposit was radiocarbon dated to 2200 ybp, some 300-400 years older than the bones in the arroyo kills for which the site is best known. In addition, we found another bison bonebed two meters deeper than the first. Although little excavation has been accomplished in this lower bonebed, we did recover a chert chip suggesting it too is the result of a bison jump. The two deposits at the base of the cliff make the Certain site the second confirmed bison jump on the southern Plains. The geomorphological history of the canyon provides the mechanism leading to the abandoning of the jump technique for the arroyo trap technique. Evidence of a shift in environmental conditions from xeric to mesic ushered in the Woodland horticulturalists.
