Work wraps up at one of ‘world’s great fossil sites’ | AspenTimes.com

Work wraps up at one of ‘world’s great fossil sites’

Janet UrquhartThe Aspen TimesAspen CO Colorado

Photo courtesy of the Denver Museum of Nature & Science

SNOWMASS VILLAGE – Ziegler Reservoir appears destined to impress right up until the fossil dig crew lays down its shovels Friday evening.A seven-week push to unearth Ice Age fossils from the spot near Snowmass Village where dam construction will begin next week has yielded 4,517 bones from at least 20 different animals, according to the tally released Thursday by the Denver Museum of Nature & Science.Some 3,000 of them may have come from mastodons, estimated Dr. Kirk Johnson, leader of the excavation team and vice president of the Research and Collections Division at the museum.Given that only three partial fragments of mastodons had been discovered in Colorado’s history before Ziegler, the collection is astounding. Bones have been recovered from very young mastodons to huge adult specimens, and everything in between.”It’s very much become a mastodon story,” Johnson said. “We’re going to have a sample of an entire growth series of mastodons, which is so cool. I don’t think anybody’s ever got that before.”The fossil dig wraps up Friday, and most of the museum staff and volunteers will return home Saturday, but Johnson is apparently unfazed by a month and a half of supervising the dig while juggling media demands and speaking engagements.”I love it here,” he blurted Thursday in a telephone call from the field, where he had just uncovered the giant jawbone of a mastodon.”It’s immense. It’s like 3 feet long,” he gushed.The discovery came on the heels of an upper leg bone that was nearly 4 feet long and took two people to carry.”We’re getting mammoth-sized mastodons,” Johnson quipped. “One of the things we’re noticing is our mastodons are really big. Maybe it’s the Colorado Rocky Mountain air.”Adult Columbian mammoths, evidence of which has also been unearthed at Ziegler, stood about 12 feet high at the shoulder, while American mastodons reached about 10 feet at the shoulder. The Ziegler mastodons are rivaling mammoths in size, Johnson said.The list of fossil finds also includes Ice Age versions of bison, deer, horse, sloth and camel, as well as a host of smaller animals, including an otter, muskrat, bat, rabbit, birds, fish, salamanders and more.Johnson predicts the species list will grow to 30 or 40 once scientists have had time to carefully examine the specimens back at the museum, where Ziegler Reservoir has made the pending construction of a 60,000-square-foot, underground preservation facility all the more timely. The museum will break ground on the facility in September.Along with a more detailed species analysis will come a multitude of scientific conclusions that will result from data collected at the site by 27 experts from around the country and the world. The last of the visiting scientists departed Wednesday.Johnson and his colleagues hope to nail down the exact age of the fossils, currently placed at 50,000 to 150,000 years old, and determine what happened that led to the death of so many animals in one place.Proferred theories include animals dying on the shore of an ancient lake and being picked apart by scavengers, their scattered remains eventually rolling down an underwater slope. Or, they could have gotten stuck and died.”We’re leaning toward some kind of a trap, just given the number of animals, but right now, we’re not able to say what the trap was,” Johnson said. “My gut feeling is, it’s something to do with the nature of the sediments in the lake.”Since we’re getting families (young and adult mastodons together), you can imagine a whole bunch of animals being killed simultaneously. Clearly, this was a dangerous place.”Though the dig officially ends Friday, allowing dam construction to begin Tuesday, a few museum staffers will remain at the site just in case the heavy machinery turns up something more.Over the past seven weeks, a rotating volunteer crew that grew to 50 in number, moved some 7,000 cubic yards of dirt – most of it by hand, with shovels – that Johnson estimates weighed about 7,000 tons. The goal was to prevent the destruction of any fossils on the end of the reservoir where a new, earthen dam will be constructed. Whatever remains in the rest of the reservoir will be back under water by year’s end, but remain protected for the future, Johnson has said.While scientific papers will ultimately result from the study that is yet to be done, Johnson has vowed to write about Ziegler for the general public’s consumption. He is already the author of “Cruisin’ the Fossil Freeway,” illustrated by Ray Troll.”I want to write about this while it’s fresh in my mind,” he said. “The story of the last nine months is a sweet story.”The reservoir, being enlarged by the Snowmass Water and Sanitation District to serve the resort’s future water needs, first emerged as a fossil treasure trove last October, when a bulldozer operator uncovered large, coffee-colored bones that turned out to be those of a Columbian mammoth.It was initially thought to be an isolated find, but more and more bones surfaced in what became a frenzied dig before winter set in. Some 600 bones and bone pieces were recovered last fall, including 15 tusks. The museum crew returned to the site May 15 to resume the effort, with a July 1 deadline.What has transpired earns Ziegler a place in the annals of paleontology, according to Johnson.”It is really one of the world’s great fossil sites,” he said.janet@aspentimes.com