Denver Museum of Nature & Science to to Continue Ice Age Fossil Excavation at Ziegler Reservoir Near Snowmass Village

The Denver Museum of Nature & Science has reached agreements with the Snowmass Water and Sanitation District (SWSD) and the State Historical Preservation Office that will allow excavation crews to return to Ziegler Reservoir in May 2011. Museum crews will spend seven weeks between May 15 and July 1 continuing the excavation of an exceptionally preserved series of Ice Age fossil sites that were first discovered in October by a bulldozer driver working on the expansion of the reservoir.

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

“We are very pleased that our collaboration with the Snowmass Water and Sanitation District and the Town of Snowmass Village will continue for another season,” said George Sparks, president and CEO of the Denver Museum of Nature & Science. “The discoveries made last fall at Ziegler Reservoir are among the most significant in Colorado history, and having additional time to excavate this spring will further enhance our scientific understanding of this amazing find.”

After the discovery of the original juvenile Columbian mammoth in mid-October, Museum excavation crews arrived at Ziegler Reservoir near Snowmass Village in early November to begin digging for additional fossils. Over a two week period, they uncovered an exceptionally well-preserved Ice Age ecosystem that produced a bumper crop of Ice Age plants and animals, including parts of

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
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

By the end of the fall 2010 excavation, Museum crews had 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. The fossils are currently being preserved in the Museum’s conservation lab in preparation for scientific study.

The agreement between the Museum and SWSD, and an excavation permit from the state archaeologist, allow Museum crews to excavate in the same area of Ziegler Reservoir where most of the fossil discoveries were made in November. Crews will remove any fossils that are in the ground below the dam construction site. This will allow SWSD to complete dam construction on schedule without damaging or burying any fossils. The Museum expects to have as many as 40 people working at the dig site at a time, including a small number of formal and informal educators from the Roaring Fork Valley who will be selected and trained as volunteers to work side by side with renowned scientists and other Museum staff doing the actual work of the excavation.The agreement also allows the Museum to leave a small excavation crew at the site after July 1, as construction continues on Ziegler Reservoir. They will recover additional fossils that might be exposed by large machinery as they excavate clay to build the dam.

The State of Colorado owns and manages fossils found on state land or land managed by smaller governmental entities including districts such as the SWSD. The fossils are preserved in designated museums for the benefit of the public. The Denver Museum of Nature & Science is the designated state repository for the Ziegler Reservoir fossils.

The Museum has assembled a team of 34 scientific experts from 15 institutions in the United States, Canada, and England to study the discoveries. Some members of the science team will be joining the excavation team at Ziegler Reservoir for a portion of the dig.

“We are really excited to return to Snowmass Village in May, and we are confident we can complete the excavation in a timely fashion that will allow Snowmass Water and Sanitation District the time they need to complete their dam and reservoir,” said Kirk Johnson, the leader of the Museum’s excavation team and vice president of the Research and Collections Division. “This is a once-in-a-lifetime opportunity and we will make sure that the fossils are properly recovered and that we accomplish the science that is needed to understand this amazing discovery.”

The Ziegler Reservoir excavation site is one of the most important paleontological sites in Colorado for several reasons:

The high-altitude setting of this fossil site (8,874 feet) is consistently underrepresented in the Ice Age fossil record.
The site contains several fossil-bearing horizons that allow for the reconstruction of a series of Ice Age ecosystems and potentially a better understanding of Ice Age climate change in the Colorado Rockies.
It is exceedingly rare to discover such a diversity of plants and animals from an Ice Age ecosystem in one place. Normally, scientists must use information from many different sites to piece together a picture of what plant and animal life was like in the Ice Age. At this site, they can assemble a very complete picture from one location.

The preservation of the fossils discovered at Ziegler Reservoir is exceptional. Plant matter found at the site is still green, and 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 45,000 years old, and geologists estimate the site could be as old as 130,000 to 150,000 years. 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.

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