Near the Rimrock Draw Rockshelter outside of Riley, Oregon, archaeologists recently discovered evidence suggesting one of the oldest known human occupations in the western U.S.

With assistance from local students, archaeologists with the BLM and the University of Oregon Archaeological Field School have been excavating at the Rimrock Draw Rockshelter since 2011. Their discoveries have included a number of stone projectile points and tooth enamel fragments likely belonging to a prehistoric camel that became extinct approximately 13,000 years ago.

But what has the archaeological community most excited is a small stone tool found below a layer of volcanic ash. Near the bottom of a 12-foot deposit, archaeologists discovered a layer of ash that was identified as volcanic ash from a Mt. St. Helens eruption about 15,800 years ago. Beneath the layer of volcanic ash, archaeologists discovered a small orange agate tool believed to have been used for scraping animal hides, butchering, and possibly carving wood. A blood residue analysis of the tool revealed animal proteins consistent with bison, the most likely species being Bison antiquus, an extinct ancestor of the modern buffalo.