ZIEGLER RESERVOIR AND THE SNOWMASTODON PROJECT: NEW HIGH-ELEVATION FOSSIL VERTEBRATE FAUNAS FROM SNOWMASS VILLAGE, COLORADO

The Snowmastodon Site, Pitkin Co., Colorado was discovered in October 2010 by heavy equipment operators during construction to expand a reservoir. The site was originally a lake formed at 8,874 feet during the Bull Lake glaciations about 150,000 years ago. The original lake area is approximately 11.5 acres in size with a total catchment of 25 acres and lacks an inlet and outlet. The sediments at the site are approximately 10 meters thick and include local gravity and debris flow deposits, airborne fine grained silts and clays, peat beds, and locally derived glacial deposits. Fossiliferous Pleistocene sediments range in age from approximately 130,000 years ago to ~45,000 years ago. More than 30 vertebrate taxa are currently identified from skeletal material and include the following. Fish: Oncorhynchus. Amphibians: Ambystoma, several Rana species, and a hylid. Squamate reptiles: natricine and crotalid snakes, and two lizards. Birds: several genera of variable size. Mammals: sloth (Megalonyx jeffersonii), bat (Microchiroptera), mink or weasel (Mustela), otter (?Lutra), chipmunk (?Tamias), two genera of voles (Microtus and Clethrionomys), field mouse (Peromyscus), muskrat (Ondatra), beaver (Castor), rabbit (Leporidae), mammoth (Mammuthus columbi), mastodon (Mammut americanum), bison (Bison latifrons), camel (Camelops), deer (Odocoileus), a large cervid, horse (Equus), and several other taxa. Large carnivores are represented only by bone gnaw marks. Two stratigraphically distinct faunas are represented: Mammuthus and Camelops are only represented in the uppermost peat deposit while Mammut and Megalonyx only occur in lower debris flow and lake margin deposits. Vertebrate specimens from the upper peat level are commonly articulated, in contrast with lower deposits where most specimens are disarticulated due to modest pre- and syndepositional transport. Excavations are complete at the site but more than 3000 kg of matrix remain to be screen-washed and sampled for medium to small vertebrates.