Scientists uncover an Ice Age ecosystem in Snowmass

By Troy Hooper
Real AspenNovember 5, 2010

SNOWMASS VILLAGE — Excavation crews uncovered a giant ground sloth and a deer-like animal Thursday at Ziegler Reservoir, raising the total prospect of Ice Age species at the site to at least five.

Giant ground sloths

Scientists additionally found evidence of two more mastodons in the area after they unearthed a juvenile mastodon tooth and a new leg bone in separate places this week. Denver Museum of Nature & Science experts say there appears to be at least five or more mastodons in the ground, one Columbian mammoth, three ancient bison, plus heaps of well-preserved plant matter and insects.

“I'm waiting for my phone to buzz to see what they're finding right now,” Kirk Johnson, the museum's chief curator and vice president of collections and research, told a large audience assembled here.

Crews are figuratively and literally just scratching the surface of this mother lode of fossils. The media and a roomful of curious residents peppered experts with excited and thoughtful questions Friday, but museum officials were quick to point out this is only the fourth day of their excavation work and there is still a lot to be uncovered and tons more to learn before some of their questions could be answered.

That said, an enormous amount of information about the scientific findings has been released.

The humerus of a giant ground sloth.

The fossil site in Snowmass is one of the most significant discoveries in Colorado history. It is unique because there are no other known sites in the state, and few in North America, that contain both mammoth and mastodon fossils in one location. Mammoths and mastodons are both elephant-like creatures with long tusks that both faded into extinction on this continent more than 12,800 years ago.

The juvenile Columbian mammoth first uncovered Oct. 14 by a worker digging in the drained reservoir appears to be the most complete mammoth fossil found at high elevation in Colorado. At about 8,870 feet, it is also the highest elevation mastodons and giant grounds sloths have been found in Colorado.

Not including the jaw-dropping finds above Snowmass Village, there have been only three other mastodons, four other giant ground sloths and 103 other mammoth discoveries on record in Colorado.

Thursday was by far the biggest day of discovery to date. In addition to the revelations of the giant ground sloth, an unidentified fawn-like creature and more mastodons, a museum volunteer watched the horn of an Ice Age bison pop out of the sediment a bulldozer was moving. The horn along with additional bison bones found in two other locations has scientists saying there are a few of them here.

A giant mastodon skull.

Three bulldozers are carefully plowing through the area with museum experts walking alongside them. Two days ago, a bulldozer clipped the top of a large skull that scientists believe is from a mastodon.

While damage to fossils can sometimes occur, the machines are necessary tools for discoveries, Johnson said. “If you don't dig, you'd never find anything. So I love bulldozers and backhoes,” he said.

The expansion of Ziegler Reservoir is ahead of schedule despite the fossil excavation project, said Snowmass Water and Sanitation Manager Kit Hamby, who museum officials have praised for the district's assistance in preserving the integrity of the site and appreciating its scientific value. The expanded reservoir is on track to be filled next year, lest historically huge findings get in the way.

Dr. Steve Holen, the Denver Museum of Nature & Science archaeology curator and mammoth expert, said he has worked a lot of sites in his 40 years on the job and never received this kind of cooperation.

“Never in my life have I seen so much support,” said Holen, adding that the historically significant discoveries made in Snowmass over the last few days have been the highlight of his long career.

Perhaps the only way Ziegler Reservoir wouldn't be filled next year is if it becomes an archaeological site. Evidence of human activity during the Ice Age would raise this area's significance even higher.

It is possible the locale is where mammoth hunters killed or butchered ancient beasts to provide food, tools and resources, Holen said, but so far there has been no evidence of any human activity at all. Scientists have set up up grids where they sift through the dirt as if it were an archaeological site.

The museum has four excavation crews recovering bones and another crew zeroing in on plant matter. As they dig, museum workers are finding different layers of sediment from two different time periods. Radiocarbon tests will better pinpoint the two different time periods. Results are expected next week.

The peat bog where the animals are buried is loaded with ancient plants and iridescent insects.

At today's public meeting in Snowmass, Dr. Ian Miller shows a slide of a giant ground sloth.
Troy Hooper

“You pull the peat apart and you see greens and reds,” said Ian Miller, chairman of the museum's earth sciences department.

Crews have found large logs, some up to three feet in diameter, where grain and growth rings are easily discernible, Miller said. And they've recovered seeds, pollen, mummified leaves, and fossilized snails that may provide clues to the water quality of the lake or bog they lived in thousands of years ago.

Ultimately scientists will be able to describe in detail the environment in which these beasts roamed.

“We'll be able to flush this forest out over time,” Miller said. “It is truly uncommon to get all parts of a fossil ecosystem preserved in one place. Instead of having just a piece of the ecosystem to tell the story, you’ve got all aspects of it. It’s one of the most exciting scientific discoveries I’ve ever worked on.”

The Denver Museum of Nature & Science has taken ownership of the heavily saturated and well-preserved bones and will put them in a climate-controlled environment so that they do not crumble.

Museum CEO George Sparks said the fossils will go on display in an expansive and expensive three-story addition planned on the south side of the museum to be called the Science Engagement Center.

“The last few weeks have been astonishing. It doesn't get any better than this,” Sparks said. “We all have to appreciate the economic impact this will have on Snowmass Village and the museum.”

To that end, Snowmass Village Town Manager Russ Forest said officials are looking at “a variety of ways to communicate this wonderful discovery with the community and with our guests.” Town and museum officials and their marketers are strategizing ways to capitalize on the site's tourism potential.

“Snowmass and the museum will never be the same again,” Sparks noted.

The economy isn't all that's on their minds. Education is at the forefront. Already, the museum has shown the fossils to more than 8,500 students in the Roaring Fork Valley and it is planning a “Mammoth and Mastodon Madness” celebration Nov. 13 in Snowmass Village for the public. A similar event will be held in Denver the following week.

“These are Colorado treasures," said Sparks. "They belong to the citizens of Colorado."

comments: 2 Comments on "Scientists uncover an Ice Age ecosystem in Snowmass"

jrix – Nov. 05, 2010, at 10:04 p.m.

Looking down from the ski hill, the Ziegler Reservoir has always appeared to be a remnant of a larger body of water and also a collecting pit at the edge of glacial activity. It's simply very old looking.
The article rightly points out the benefit of bulldozing and construction. Otherwise, no one would go to the trouble of digging beyond the first clay layer.
It is a relief to see cooperation between the construction company and the paleontologists. My interest is to learn about the predators of the animals that have washed into the ancient pit.

snowmasstodon – Nov. 14, 2010, at 8:47 a.m.

Now that was worth the hr. long wait. What an incredible find in the high country. This will put Snowmass on the world stage for a while. Plus it isn't all ski related. It should help Snowmass establish an identity for year round tourisim. If and only if the Mammoth political machine does'nt bog down in the ancient peat. For more visit

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