Tremors Could Have Deposited Thousands Of Fossils

Just before beginning his weekend on Friday, Dr. Kirk Johnson of the Denver Museum of Nature and Science received some exciting news.

"We found a baby ground sloth," said Johnson, the chief curator at the museum."We found it about an hour ago. It is pretty exciting."

The fossil of the adolescent Jefferson's ground sloth is the first discovered and just one of many discoveries that have come from the Snowmastadon Project.

The Snowmastadon Project began in the summer of 2010 when construction crews excavating earth to enlarge the Ziegler Reservoir outside of the resort town of Snowmass unearthed the bones of a juvenile mammoth.
© Jan Vriesen

Since that small discovery, teams of paleontologists squeezed in two large digs that produced a bevy of fossils that surprised even them.

"This one is so good it's a once-in-a-lifetime find," Johnson said.

Mastodon, Giant Bison, Mammoths And Ground Sloth

Johnson said that scientists have discovered 5,426 bones.

"We don't even know how many animals that is now," he said.

Johnson estimates that they have more than 50 animals representing at least 40 species in their collection. Some of the species represented include mastodon, ground sloth, mammoth, camel, giant bison, horse and deer.

The dig officially ended in June. After the postponement, construction crews went back to work on the reservoir.

"We kept people up there during the construction and found fossils all the way through," Johnson said.

Earthquakes And Quicksand

One of the things that puzzled paleontologists was how they were able to stumble across such a rich and intact find.

"We are finding these beautiful bones that were perfectly preserved," Johnson said. "But they were separated instead of whole skeletons. Then we found these bones in these layers that were debris flows."

Johnson said scientists knew that a prehistoric lake existed at the site around the time when the fossils were buried.

"We were trying to figure out what would kill animals at the edge of the lake," he said.

Johnson said scientists believe that the more than 30 mastodons uncovered at the site were entrapped by quicksand. He said they have seen that sometimes after an earthquake, sediment in riparian areas become like quicksand.

Johnson said that would explain how both adults and children were found at the site.

Johnson said a following earthquake could have then caused another debris flow that would have then buried the remains of the giant prehistoric mammals.

"So we had death, then a period of time, then deposit," Johnson said.

To prove the hypothesis, Johnson said scientists will cut open some of the tusks found. He said they can count the rings in the tusk like a person can count tree rings to determine the age of the animals and when they died.

Displaying The Fossils

Johnson said scientists are still cataloging and determining what fossils they have unearthed. After that process is completed, museum staff will then decide how and what they will display of the remains.

"Do we have entire skeletons?" Johnson said. "These are things we are still trying to determine."