LATE PLEISTOCENE COLUMBIAN MAMMOTH, SHORT-FACED BEAR, GIANT BISON, AND COLUMBIAN GROUND SQUIRREL FOSSILS FROM THE AIRPORT LANE SITE, LA GRANDE, NE OREGON

The late Pleistocene (12,950 ± 50 ¹⁴C years BP) fossils found at the Airport Lane site in the southern Grande Ronde Valley in January 2010 include the first juvenile Columbian mammoth (Mammuthus columbi), giant short-faced bear (Arctodus simus simus), and giant bison (Bison antiquus antiquus) fossils found in the region. The partial skeleton of a Columbian ground squirrel at the site is the first fossil of this species found in Oregon. The presence of Columbian ground squirrels and the microfossils (diatoms, sponge spicules, and grass, juniper, western hemlock, and pondweed pollen in the silty sand at the site indicate cooler and wetter conditions during the late Pleistocene than at present. The bison, mammoth, and bear found at the Airport Lane site may have drowned in a spring flood or a jökulhaup released when an ice dam in the nearby mountains burst. The bones found at the site (a tibia and tusks from the mammoth; the articulated vertebrae (T-13 to L-5), an articulated radius/ulna and carpals, and a calcaneus from the bison; and the proximal end of the femur of a bison) are those typically found at butchering sites. This suggests the alternate hypothesis that the large mammals found at the site may have been killed and butchered by late Pleistocene hunters.