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Fossil Discovery Makes History: Studying a Prehistoric Climate and Ecosystem in Colorado

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Detailed Description

A trio of USGS scientists has been involved in the excavation and study of a major animal and plant fossil discovery in Snowmass Village, Colo., which provides more than 100,000 years of vegetation and climate records for the area. This recent find includes Columbian mammoths, mastodons, extinct bison, Ice Age deer, and a 9-foot ground sloth, and the USGS team is studying fossil-bearing sediments to determine the age of the fossils and the environment in which the prehistoric organisms lived. Jeff Pigati, a scientist on the USGS team which also includes Tom Ager and Paul Carrara, discusses this Denver Museum of Nature and Science-coordinated project.




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[Intro Music]

Marisa Lubeck: Welcome, and thanks for listening to this episode of USGS CoreCast. I’m Marisa Lubeck. A trio of USGS scientists has been involved in the excavation and study of a major animal and plant fossil discovery in Snowmass Village, Colorado.

This recent find includes Columbian mammoths, mastodons, extinct bison, Ice Age deer, and a 9-foot ground sloth, and the USGS team is studying fossil-bearing sediments that appeared encompass more than 100,000 years of prehistoric time.

Coordinated by the Denver Museum of Nature and Science, the project has been a unique experience for the USGS team. I’m here with USGS scientist, Jeff Pigati, who along with his colleges is working to determine the age of the fossils and the environment in which these animals and plants lived. Thanks for talking with us Jeff.

Jeff Pigati: Thanks Marisa. Thanks for having me.

Marisa Lubeck: Jeff, what was it like being part of the Snowmass crew and seeing these fossils first hand on the site? What was the atmosphere like?

Jeff Pigati: It was very exciting Marisa. I’ve never been in a site quite like this. The site was probably the size of a football field or so. There were people working everywhere and at incredible speeds, we knew that snow was coming in soon, so we were trying to get as much work done as we could. And to see the bones emerging from the ground, was kind of like a dream.



There were bones just pouring out of the ground. We were finding bones at the rate of maybe, a bone every few minutes. And we had people working all over the place with bulldozers and scientists from the museum that we kind of directing things. And it was an incredible, incredible experience.

Marisa Lubeck: What’s the significance of these fossils in terms of their utility for USGS science? Why are sediments preserved from 130,000 years ago relevant today?

Jeff Pigati: The fossils are not the only part of the story. A couple of our missions here at the Survey are to, one, reconstruct climate of the past—particularly drier parts in the Western US, more elevated areas like we’re working at at Snowmass. And the reason we’re interested in these places is that they are very sensitive to climate change.



And so if we understand how the climate changes there in the past, then perhaps we can get a better handle of what we might expect in the future. Another part of our mandate at the USGS is to better understand how ecosystems work.

We have very little information on what it was like in the past at that high elevation. Records like the one that we’re working at the Snowmass simply don’t exist. We’re looking at 50 to 100,000 years of sediments. And in these sediments, there is a number of different types of information that are available.

We can look at things like pollen and plant macrofossils to reconstruct what the vegetation was like in the past. We can look at things like ostrocod and other types of microfauna. These are very small invertebrates that live in lakes. And they can tell us something about the water itself; the water chemistry, the temperature and so on and so forth.

The Snowmass site is about 8900 feet in elevation, so we can get a glimpse into this window of what it was like in the past up at high elevation where we really don’t have any information that exists today.

Marisa Lubeck: And Jeff, what preliminary findings have you observed so far?

Jeff Pigati: When we were out in the field, our main task was to describe the stratigraphy, the sediments that are present at the site. We want to understand how old these sediments are. What types of fossils that are in there. We want to understand what kind of vegetation was present. So the sediments act kind of as a book, kind of as an archive of these different pieces of information.



So we described and we measured the different sections. There are very large changes at the Snowmass site in terms of color of the sediments, the types of sediments, the grain size, the amount of organic matter. It’s particularly unique in that it’s a pretty small area. But the changes that we see in the sediments are very, very large. There’s really striking contrast between the amount of let’s say organic matter in certain parts of the deposits versus elsewhere.

So what that tells us is that there were very large changes most likely in climate and certainly in the vegetation around the lake in the past. And so while we’re at the site, we measure the section. We describe it. We collect samples for things like radio-carbon dating, pollen and plant microfossils, grain size, chemistry. And what we want to do in this first round of research is to understand where we at in time, understand where we’re at in terms of vegetation, and put together a framework from which we can do the further studies which will commence again next May.



Marisa Lubeck: And in these coming months, what sort of information will you be looking for and what methods will you apply? For example, what information do you expect the carbon-14 dating and pollen analyses to provide?

Jeff Pigati: We found that the entire section is greater than what we can actually reach with radio-carbon dating in terms of age. Which means, these sediments are at least 45- or 50,000 years old. So we’ve got to turn to other methods for additional dating—things like luminescence and uranium series—different techniques that can push the time range back further.

What we’ll do over the next few months is take some of these preliminary samples that we’ve collected. We’ll take some of the bones that we’ve collected and will actually start dating them directly. The other thing that we’ll be doing is pollen analysis. We’ll look at the types of vegetation that were present throughout the section.

And what we did in this first round of collection is to simply take representative samples of each one of the different units that are present. We’ll get a broad idea of the different types of vegetation. But the next step, going back in May and in June of next year, will be to collect continuous samples. We’ll take several cores. We’ll take more sediment from the exposures that are available. And we’ll do a more detailed inspection of both the vegetation and the climate and as it changed through time.



Marisa Lubeck: This excavation was coordinated by the Denver Museum of Nature and Science. Why and how did the USGS become involved in this project?

Jeff Pigati: We’ve got a lot of different folks that have worked in what we call the Quaternary. This is the last two, maybe two and a half million years or so. We’ve got a lot of expertise on our team and in the USGS in general working on reconstructing vegetation and climate in this timeframe. The museum folks, Ian Miller and Kirk Johnson, the guys that are in charge of this, work a little bit deeper in time.

Ian for example works in the cretaceous, which is the time of dinosaurs. So, we’re talking about tens to hundreds of millions of years ago. It’s a different approach to science. There’s this more of a hard rock type of approach whereas as we study loose sediments, dirt, things like that to get information on the last couple of million years.

So when the museum was contacted about excavating the first mammoth that was found, they realized pretty quickly that the site was very special in terms of the type of megafauna that were being produced. And they wanted to get a good handle on the climate and the vegetation history of this timeframe. And they knew that they needed people to bring in their expertise to work on this kind of thing.



Marisa Lubeck: How long will your research last? And when will you have more concrete results or findings?

Jeff Pigati: Typically, research is kind of an open-ended thing. We go to the site, we come back with samples, we work on them, we go back to the site and we repeat this process until we kind of have a story to tell. This is a little bit different because the site was initially discovered when the reservoir was drained and is being enlarged.

This reservoir provides water to the village of Snowmass and a little bit of water to the ski area for making snow. This reservoir actually has to be refilled by early November of next year, which basically means we have one summer. We’ve got one summer to do the entire project. All of the fieldwork that can be had has to be done by early next summer, so that they can start to fill this reservoir again.

So research is going on at a breakneck speed across many disciplines all at the same time. And we’ll go back again in late May and then stay probably through June after the snow melts. And we expect to have the entire thing wrapped up by 2013, about two years to do the entire project,which is an incredibly short amount of time for the amount of work and the amount of information that is available at the site.



Marisa Lubeck: Was there a specific moment or event during your time on site that especially resonated with you?

Jeff Pigati: I can’t tell you how many times we would catch ourselves looking at each other and smiling and just saying, “I can’t believe this place.” We were pulling out tusks several feet long. They pulled out a 7-foot tusk at one point. And the bones and the tusks are so beautifully preserved that you can literally wipe off the dirt and see your reflection in the ivory.

This kind of thing just doesn’t happen. And similarly we found seeds and beetle parts and insects, and all kind of plant macrofossils. They look like these plants were alive yesterday. And at one point, we took some of the material and opened it up. And not only were there plant remains, there were actually plants present. These are 40 and 50-thousand-year-old plants that were still green.

The one moment that really resonated with me though is that the people out there, they were very excited to be there. Their enthusiasm was infectious. And at one point, I was working on one of the outcrops, it was cold and kind of nasty out there, and there was another guy—he was a volunteer with the museum who’s been doing casting of bones for something like 17 years now.



And at one point, I look over and he’s lying down in his ditch that he had dug for himself to kind of stay out of the wind. On his side, lying in the mud working on this tusk. And it’s snowing sideways. It’s cold. He catches my eye and he gives this huge grin and yells across the wind, “This is awesome.” It was that kind of atmosphere which after a while you can smile to yourself, and you think, “You know what, this really is awesome.”

Marisa Lubeck: Well, thanks again for taking the time to share your experience with us Jeff.

Jeff Pigati: You’re certainly welcome Marisa. Thanks very much.

Marisa Lubeck: This podcast is a product of the US Geological Survey, Department of the Interior. I’m Marisa Lubeck. Thanks for listening.



Show Transcript