Snowmass fossil site continues to be ‘treasure trove’
Day by day, an Ice Age fossil site discovered last fall near Snowmass Village is continuing to grow in stature and scientific importance as excavators retrieve bones by the boxes full.
The Denver Museum of Nature & Science resumed digging at the site this spring, and by Thursday night had racked up 864 fossils, even more than the 600 or so found last fall.
“We’re pulling out about a hundred bones a day now,” said paleontologist Kirk Johnson, who is leading the excavation for the museum.
He said the success of the excavation and its discoveries are exceeding expectations.
“It’s really a treasure trove. It’s amazing,” he said.
The first discovery of fossils occurred Oct. 14, when a contractor unearthed bones from a Columbian mammoth during expansion of a reservoir for the town of Snowmass Village. Within a month, excavators unearthed bones from another mammoth, and from mastodons, an Ice Age bison, a Jefferson’s ground sloth, an Ice Age deer and other animals.
Previously, only three mastodons had been discovered in Colorado. The Jefferson’s ground sloth discovery was a first for Colorado, and Snowmass was the only place in Colorado, and one of few places in North America, where mammoths and mastodons have been found in the same location.
This spring’s discoveries include an Ice Age camel and parts of other animals that have yet to be identified. But, Johnson said, “It’s really turning into a mastodon story this year. Boy, we’re going to have a smashing collection of mastodons in Denver.”
The museum had trademarked a name — the Snowmastodon Project — that has become particularly fitting in light of this spring’s findings. Johnson said crews this year have discovered the bottom of an ancient lake bed covered with skulls, tusks, limb bones and other mastodon fossils, from infant to adult. They’ve found a 7-inch thigh bone believed to have come from a fetal mastodon, which compares with the 4-foot thighs of adults.
With as many as 27 tusks discovered to date, that means a minimum of 14 mastodon discoveries, which compares with a record of 31 at any one site. But researchers won’t know how many individual animals they’ve discovered until they’ve had a closer look at the fossils, Johnson said.
Also being discovered at the same level are fossils of trees and an abundance of pollen that suggest the mastodons lived in a warmer, interglacial period of probably more than 100,000 years ago.
“It looks … like the animals just lived and died along the shores of this lake, and the lake was very efficient in accumulating and preserving the bones,” Johnson said.
That contrasts with a higher layer of peat where mammoths, bison and deer were found, in some cases apparently because they became stuck in the peat and couldn’t escape.
When they first resumed digging at the site, excavation crews this spring could relate to those animals’ fates. For the first 11 days, heavy snow and other precipitation resulted in about one-third of those working on-site each day finding themselves stuck in mud, Johnson said.
“It was a total quagmire,” he said.
This is the museum’s largest fossil-excavation project. By Friday, the resumption of digging was in its 21st day.
“We’ve pulled together a great team of 36 scientists from 17 universities in four countries, and they’re really deeply engaged,” Johnson said.
Also on-site are 107 trained volunteers, 35 staff members and nine interns. Another dozen or so people will join the crew this weekend, and a group of local educators also has been selected to help out this month and share their experiences with students and their communities.
Johnson said a few “expert dinosaur diggers” have been recruited to help protect the numerous big bones being discovered by encasing them in plaster.
The crews have until July 1 to finish work on what is considered the best Ice Age fossil site in Colorado and best high-elevation Ice Age site in North America. After that, the Snowmass Water & Sanitation District needs to resume enlargement of the reservoir in order to help meet the town’s water needs.
Johnson said an observer or two will remain on-site during construction work this summer to keep an eye out for any other fossils that might surface.
The reservoir will be lined with impermeable clay, and any fossils not yet uncovered will remain protected and in place, awaiting possible excavation in some future generation after the reservoir is decommissioned.
Because of the hurry to keep digging this spring, no public access is being provided to the dig site. A staffed, interpretative display can be found at the Snowmass Mall in Snowmass Village all summer, and on June 18–19, the Snowmass Ice Age Spectacular is planned, featuring unearthed bones and live broadcasts from the dig site.
Johnson said there will be a public talk June 15 at Colorado Mountain College in Glenwood Springs and two public events June 23 at the Aspen Institute.
The water district, town and museum have set a $1 million fundraising goal to help cover excavation, preservation, public outreach and other aspects of the project. With a recent $100,000 donation by the Crown family, which owns the Aspen Skiing Co., $460,000 has been raised to date.
As excited as Johnson is about the discoveries at the site to date, he said one thing noticeably lacking is any carnivore fossils. Scientists still hope to find signs of predators such as wolves, bears or saber-toothed tigers.
“There’s some cool animals that ought to be here that we haven’t seen yet,” he said.