Tests reveal fossils are at least 43,500 years old

By Troy Hooper
Real AspenNovember 12, 2010
The first radiocarbon tests of Ziegler Reservoir reveal some fossils found there are at least 43,500 years old.
Dr. Kirk Johnson holds a sloth tooth.
Denver Museum of Nature & Science


Scientists tested samples from a piece of wood that was located beside an American mastodon in the lowest layer of the dig site and determined they were radiocarbon dead. That suggests fossils found in the silt layers at the bottom of the reservoir have been there 43,500 years, or exponentially longer.

Denver Museum of Nature & Science experts believe the fossils found in the reservoir above Snowmass Village are quite possibly from two different time periods, but more study is required. So far, multiple Ice Age mastodons, mammoths, bison, deer, a Jefferson's sloth, small reptile, small mouse-like mammal, snails and insects have been unearthed in Snowmass. There also is evidence of beavers.

The bones of a young Columbian female mammoth found Oct. 14 by a Gould Construction worker expanding the reservoir were initially estimated to are currently estimated at between 12,000 and 16,000 years old. Mammoths went extinct thousands of years ago but date back a few million years.

Ice age bison like the ones unearthed in Snowmass are usually found in American West sediments that are 30,000 to 50,000 years old. The U.S. Geological Survey Additional is conducting additional testing and analysis that should tell scientists more about the age of the sediment layers in the fossil site.

A new bone bed also exposed this week after crews removed a seven-foot American mastodon tusk from the earth. The bone bed includes fossils from an American mastodon, an Ice Age bison, an Ice Age deer and a well-preserved sloth tooth, which officials called a “real find” in the excavation.

All of the bones on the site will be washed in museum's conservation lab where scientists will closely inspect the fossils to determine how the animals died, and what happened to them after they passed.

The dig site is at about 8,870 feet — the highest elevation mastodons and giant grounds sloths have been found in Colorado. Remains of the Jefferson's sloth are the first ever recorded in Colorado. Moreover, there are no other known sites in the state that contain both mammoth and mastodon fossils.

A museum photographer is documenting the removal of the Columbian mammoth fossil discovered on Oct. 14. A temporary tent is sheltering the bones while the photographer shoots away so that a three-dimensional visualization of the original position of the fossils can be created on a computer.

Just beyond the dig site, the runs on Snowmass Ski Area are accruing more man-made and natural snow. It serves as a reminder that there aren't many days left this year for the Ice Age ecosystem excavation. With each day, the frozen ground is becoming harder to penetrate. Work may wind down in a few days.

A Denver Museum of Nature & Science excavation crew works on a new bone bed discovered Wednesday at Ziegler Reservoir. Thus far, the bones of an American mastodon, an Ice Age bison, an Ice Age deer, and a sloth tooth have been recovered in the new bone bed, officials say.
Denver Museum of Nature & Science


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