AMS Dating of the Late Pleistocene Mammals at the Colorado Creek Site, Interior Western Alaska

The Colorado Creek section of Alaska is an important paleontological site first excavated and reported on in the early 1980s and 1990s. The remains of two individual mammoths (the “Upper” and “Lower”), and elements of horse, bison, and caribou make this a unique faunal assemblage for a region in interior western Alaska, and the western edge of eastern Beringia. The mammoth remains were the only portions of the faunal assemblage radiocarbon dated in the 1980s. The Upper mammoth ages were widespread between 13,000 and 16,200 BP with the older dates being more accepted for the death of the individual. A single age on the Lower mammoth was produced at 22,880 14C yr BP. New accelerator mass spectrometry (AMS) dates generally confirm the accepted ages for the two mammoths and provide more precise ages of 16,200 ± 50 and 22,710 ± 90 14C yr BP for the Upper and Lower mammoths, respectively. AMS dates on caribou and horse are similar to ages on the Upper mammoth and show an overlap in their ecological ranges in interior western Alaska between 16,000 and 17,000 14C yr BP during the Late Glacial, similar to other areas of the state. The sole AMS date on bison produced an infinite 14C age (>43,500 14C yr BP), considerably older than the Upper and Lower mammoths’ remains, and indicates that older deposits are present at the site. A dearth of dated Quaternary paleontological specimens from western Alaska hinders our understanding of this region's paleoecology. This study enhances our conception of the geographic and chronological spread of late Pleistocene large terrestrial mammals in Alaska and Beringia.