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Denver Museum of Nature & Science Concludes Successful Excavation of Ice Age Fossil Site Near Snowmass Village

Exceptional Significance of the Fossil Ecosystem Becoming Increasingly Apparent

After a month of frenetic activity, Denver Museum of Nature & Science scientists and volunteers have finished their initial excavation of the Ice Age fossil site discovered at Ziegler Reservoir near Snowmass Village, and have returned to the Museum in Denver to prepare for the next phase of scientific analysis. Although the team has been working on the site for only a few weeks and in-depth scientific analysis has yet to begin, scientists acknowledge the site is one of the most significant discoveries made in Colorado.

Denver Museum of Nature & Science staff and volunteers at the Ziegler Reservoir excavation site near Snowmass Village Copyright © Denver Museum of Nature & Science

“The discovery near Snowmass Village is one of those once-in-a-lifetime finds. Not only will it completely shape our understanding of life in the Rockies during the Ice Age, but it will become forever iconic for the kids of Colorado,” said Dr. Kirk Johnson, the Museum’s chief curator and vice president of the Research and Collections Division.

Construction crews working on the expansion of Ziegler Reservoir made the original discovery of a juvenile Columbian mammoth on October 14. After completing an agreement with the Snowmass Water and Sanitation District on October 29, Museum excavation crews arrived at Ziegler Reservoir on November 2 to begin digging for additional fossils. Over the next two weeks, they uncovered an exceptionally well-preserved Ice Age ecosystem that produced a bumper crop of Ice Age plants and animals. Excavation crews have recovered
Eight to 10 American mastodons
Four Columbian mammoths
Two Ice Age deer
Four Ice Age bison
One Jefferson’s ground sloth (the first ever found in Colorado)
One tiger salamander
Distinctly chewed wood that provides evidence of Ice Age beavers
Insects including iridescent beetles
Snails and microscopic crustaceans called ostracods
Large quantities of well-preserved wood, seeds, cones, and leaves of white spruce, sub-alpine fir, sedges, seeds, and other plants
Museum excavation crews recovered approximately 600 bones and bone pieces from the Ziegler Reservoir site, including 15 tusks, two tusk tips, and 14 bags full of tusk fragments from the mammoths and mastodons, plus hundreds of pounds of plant matter. All of the fossil bone specimens and tusks will be cleaned and preserved in the Museum’s conservation lab. Because the fossils were saturated with water when they were uncovered, drying the bones could take as long as a year, perhaps longer. If the fossils dry too quickly, they will crack and disintegrate.

Though the discovery is barely a month old, the significance and uniqueness of the Ziegler Reservoir fossil site is readily apparent to scientists.

The high-altitude setting of this fossil site (8,874 feet) is consistently underrepresented in the Ice Age fossil record. “There have been suggestions that high-altitude environments might have harbored different communities, or had a different story of change, but since fossils representing them are so rarely found, no one has known for sure. Now is our chance to see what they are like,” said Dr. Daniel Fisher, a mastodon expert from the University of Michigan, and a scientific consultant on the excavation.

In addition, it is exceedingly rare to discover so many different plants and animals from an Ice Age ecosystem in one place. Normally, scientists must piece together a picture of what plant and animal life was like in the Ice Age from many different sites. Here, they can assemble a very complete picture from one site.
The preservation of the fossils discovered at Ziegler Reservoir is exceptional. At least one of the tusks recovered from the site is still white after tens of thousands of years. Scientists think there is a good chance of recovering well-preserved ancient DNA from some of the fossils.

The age of the site is also of particular interest to scientists. Initial radiocarbon dating indicates that the Ziegler Reservoir site is more than 43,500 years old, and geologists estimate the site could be as old as 130,000 years. Additional analysis will provide more specific dating of the site. No matter what the result, the discovery of such an old Ice Age site is very rare and will provide scientists with an opportunity to learn about an earlier part of Ice Age history.

Finally, there are only a couple of other places in North America where such a great number of American mastodons are preserved in one place.

In order to ensure a thorough analysis of this Ice Age ecosystem, the Museum is assembling a scientific advisory team of leading Ice Age experts to assist the Museum’s own scientific staff. Members of the team are
Dr. Kirk Johnson, the Museum’s chief curator and vice president of the Research and Collections Division
Dr. Ian Miller, the Museum’s curator of paleontology and chair of the Earth Science Department
Dr. Steve Holen, curator of archaeology and the Museum’s most knowledgeable mammoth specialist
Dr. Richard Stucky, the Museum’s curator of paleoecology and evolution
Dr. Russell Graham, an Ice Age mammal specialist from Pennsylvania State University
Dr. Daniel Fisher, an internationally renowned expert on mammoths and mastodons from the University of Michigan
Dr. Greg McDonald, a fossil sloth expert and paleontologist with the National Park Service
Dr. Jeff Pigati, paleoecologist from the U.S. Geological Survey
Dr. Paul Carrara, a geologist from the U.S. Geological Survey
Dr. Tom Ager, a palynologist, or pollen specialist, from the U.S. Geological Survey
Dr. Steve Jackson, a fossil plant specialist from the University of Wyoming In the near term, the Museum team will focus on the preservation of the fossil specimens recovered from Ziegler Reservoir, assemble its research plan in consultation with the scientific advisory team, and raise funds to conduct scientific analysis of the specimens.
The Museum is hoping to return to Ziegler Reservoir for several weeks in the spring to continue excavations at the site, though plans have yet to be finalized. Discussions between the Museum and the Snowmass Water and Sanitation District about the spring 2011 excavation will take place over the winter.

About the Denver Museum of Nature & Science
The Denver Museum of Nature & Science is the Rocky Mountain Region’s leading resource for informal science education. A variety of engaging exhibits, discussions and activities help Museum visitors celebrate and understand the natural wonders of Colorado, Earth and the universe. The Museum is located at 2001 Colorado Blvd., Denver, CO, 80205. To learn more about the Museum, check, or call 303-370-6000.

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