VOLCANO MADNESS: [Geology2] Science Documents Mammoth Findings CO Site

Monday, November 24, 2014

[Geology2] Science Documents Mammoth Findings CO Site

Science Documents Mammoth Climate Findings at Legendary Snowmastodon Ice Age Site, Colorado

Posted on November 24, 2014 at 9:58 am
Last update 12:11 pm By: Pete Modreski, pmodresk@usgs.gov, Jeff Pigati, jpigati@usgs.gov, Heidi Koontz, hkoontz@usgs.gov, Marisa Lubeck, mlubeck@usgs.gov, Maura O'Neal, Maura.oneal@dmns.org

Mastodon Fossil

Columbian Mammoth Discovery Thrills and Puzzles Scientists

Four years ago, a bulldozer operator turned over some bones during construction at Ziegler Reservoir near Snowmass Village, Colorado. Scientists called to the scene confirmed the bones were those of a juvenile Columbian mammoth, setting off a frenzy of excavation, scientific analysis and international media attention.

"Nothing beats pulling fossils out of the ground," said project scientist Dr. Jeff Pigati of the U.S. Geological Survey. "But this site also lets us see what the Colorado Rockies were like during a period of time that we simply couldn't reach before the discovery."

This dramatic and unexpected discovery culminates next month with the publication of the Snowmastodon Project Science Volume in the international journal Quaternary Research.

Fourteen papers by 47 authors from the United States and abroad collectively represent "a new benchmark for understanding climate change in the American West," said paleontologist Dr. Ian Miller, co-leader of the Snowmastodon Project and chair of the Denver Museum of Nature & Science's Earth Sciences Department.

Historic Finding

The Snowmastodon site was an ancient lake that filled with sediment between 140,000 and 55,000 years ago preserving a series of Ice Age fossil ecosystems. Particularly fortuitous is the high-elevation locale, providing first-time documentation of alpine ecosystems during the last interglacial period between about 130,000 and 110,000 years ago. Because scientists were able to collect and study such a wide range of fauna and flora — from tiny specks of pollen to the bones of giant mastodons — the site emerged as a trove of information that will inspire future research for years to come.

"This project was unprecedented in its size, speed, and depth of collaboration," said excavation team co-leader Dr. Kirk Johnson, formerly with DMNS and now the Sant Director of the Smithsonian's National Museum of Natural History "The science volume now moves beyond the pure excitement of the discovery to the presentation of its hard science and its implications for understanding the biological and climate history of the Rocky Mountain region."

Several key research questions have emerged from study of the site:

What does the site, which is at 8874 feet above sea level, tell us about Pleistocene climate and biota at high elevations in the Ice Age Rockies?
How and when did vegetation and climate change in the past?
Did environmental changes at the site mimic what was happening globally?
How did large mammals respond to changes in vegetation and climate?
What information can we ascertain regarding the life histories of the site's proboscideans (mammoths and mastodons)?

The site's ecosystems — plants, insects, and animals combined — varied dramatically in response to climate change. "In other words, turn the climate dial a little and the ecosystems change considerably," Miller said. "We were surprised to find that certain periods in the record that seem to be cool elsewhere in North America were quite warm in the central Rockies."

The opposite was true as well. Other periods that seem only to be cool elsewhere were extremely cold in the central Rockies. The implication is that alpine ecosystems respond differently to climate change than other, lower elevation ecosystems. These new results have huge implications for predicting present-day climate change in Colorado and beyond.

Thousands of Bones

During a total of 69 days in 2010 and 2011, the scientists pulled 5,000 large bones and more than 22,000 tiny bones representing 50 different species. The site is notable for portions of more than 35 American mastodons that were recovered, representing both genders as well as a variety of ages, from calves to full-grown adults.

"We had no idea that the high Rockies were filled with American mastodons during the last interglacial period," Miller said.

Initially, scientists proposed a hypothesis that many of the mastodons had been trapped in lake sediments that transformed into quicksand during an earthquake or series of quakes. This "shake-kill-shake-bury" theory was covered in a NOVA‐National Geographic program about the project, broadcast in early 2012. "But that initial idea was too simple," said Miller. "As we learned more and studied the bones themselves, some of the mastodons do appear to have died en masse; the cause remains unclear, although a catastrophe is still possible. Other animals seem to have died sporadically. In those cases, we think the animals were simply visiting a favorite watering hole, died of various causes, and then were scavenged."

Climatic Questions and Answers?

Usually fossil sites preserve only snapshots in time. Scientists investigate lots of them and piece together what they learn to understand different time periods in the past. By contrast, the Snowmastodon site captures a nearly continuous 85,000-year time span. As a result, the site provides the best-known record of life and climate at high elevation anywhere in North America.

"We are fortunate that this natural laboratory sits in our backyard," said Pigati. "We look forward to many more years of cooperative research at the site."