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The Snowmastodon Project

Project Chief: Jeff Pigati

In October 2010, construction crews working to expand the capacity of a reservoir near Snowmass Village, Colorado, unearthed several bones of a juvenile Columbian mammoth. The discovery set off excavation and recovery efforts in which scientists and volunteers from the Denver Museum of Nature & Science (DMNS) recovered more than 5000 bones in two short field seasons ending in July 2011. The fossils included at least seven large mammals: American mastodon, the giant Bison latifrons, Jefferson's ground sloth, Columbian mammoth, ice-age deer, horse, and camel, as well as a number of smaller animals—rodents, salamanders, reptiles, snakes, fish, and birds. In addition to the vertebrate fossils, the site is host to exceptionally well-preserved plant, insect and aquatic invertebrate fossils—beetle parts are iridescent, plants are still green, and conifer cones are intact.

The "Snowmastodon" site sits in a small ridgetop catchment with no inflowing streams suggesting that the Pleistocene lake filled slowly with eolian sediment, and minor contributions from slope wash and localized debris flows. Sediments at the site appear to be continuous, and likely represent the time interval between ~50,000 and 150,000 years BP. Thus, as a whole, the site represents the first relatively complete sequence of Pleistocene ecosystems at high elevation in the Rocky Mountains in this time period, and offers a rare opportunity to investigate how these fragile ecosystems responded to past changes in climate.

Nearly forty scientists from the United States, Canada, England, and Spain are working to reconstruct climate, vegetation, and hydrologic conditions at the site. To date, several key research questions have emerged:

1. What does the site, which is at 8874 feet above sea level, tell us about Pleistocene climate and biota at high elevations in the Ice Age Rockies?
2. How and when did vegetation and climate change in the past?
3. How did large mammals respond to changes in vegetation and climate?
4. What information can we ascertain regarding the life histories of the site's proboscideans (mammoths and mastodons)?
5. Is there any evidence for human activity at the site?

Researchers from the U.S. Geological Survey, the Denver Museum of Nature & Science, and sixteen other institutions are working on these questions and more to better understand how high-elevation ecosystems in North America responded to climate change in the past, and what they might tell us about the future.

Project Publications

Carrara, P., Pigati, J.S., and Bryant, B., 2011, Formation of the "Snowmastodon" site—a death trap for late Pleistocene animals, Snowmass Village, Colorado: Geological Society of America abstract.

Gray, H., Mahan, S.A., and Pigati, J.S., 2011, A well-preserved sequence of high-elevation Ice Age ecosystems: can the Ziegler Reservoir site, Snowmass, CO be dated using optically stimulated luminescence?: Geological Society of America abstract.

Johnson, K.R., Miller, I.M., Sertich, J., Stucky, R., Fisher, D.C., and Pigati, J.S., 2011, Ziegler Reservoir and the Snowmastodon Project: overview and geologic setting of a recently discovered series of high-elevation Pleistocene ecosystems near Snowmass Village, Colorado: Geological Society of America abstract.

Johnson, K.R., Miller, I.M., Stucky, R.S., Pigati, J.S., and Holen, S., 2011, Ziegler Reservoir and the Snowmastodon Project: Overview and geologic setting of a recently discovered series of high-elevation Pleistocene (Sangamonian) ecosystems near Snowmass Village, Colorado: Society of Vertebrate Paleontology Annual Meeting abstract.

Lugo-Centeno, C.M., Pigati, J.S., and Schweig, E.S., 2011, The Snowmastodon Site: investigation of the yellow-banded silt: Geological Society of America abstract.

Stucky, R., Sertich, J., Johnson, K.R., Miller, I., Fisher, D.C., Graham, R.W., McDonald, H.G., and Pigati, J.S., 2011, Ziegler Reservoir and the Snowmastodon Project: new high-elevation fossil vertebrate faunas from Snowmass Village, Colorado: Geological Society of America abstract.