Snowmastodon Fossil Discovery: Mastodons, Mammoths, Camels and Giant Sloths in Alpine Colorado

Near the top of a 9000-foot-high mountain ridge lies a small reservoir dug out of an alpine meadow. Today, the Ziegler Reservoir acts as a water source for the ski village of Snowmass, Colorado, but long before this site was an alpine meadow, it was an ancient lake around whose shores lived mastodons, mammoths, camels—yes camels!—giant bison, and taller-than-human giant sloths. It may be hard to imagine the Rocky Mountains inhabited by these extinct megafauna (large mammals) but the evidence they left behind leaves no doubt of their existence. In fact, these animals didn’t simply represent a small number of wayward migrants that happened to stumble into western North America from their normal home range. Rather, they formed a ubiquitous and established community of fauna that inhabited vast portions of the West.

Since these species no longer are found in Colorado, or anywhere else on earth, one might wonder: when did these animals live in Colorado? How long did they live there and how did they get there in the first place? We will explore these questions below and in two additional articles in our quest to understand the origins of the Snowmastodon megafauna.

A short history of the Snowmastodon fossil site

A 2010 excavation to create a reservoir uncovered hundreds of large bones in  ancient lake sediments. A paleontological salvage effort was quickly arranged that became known as the “Snowmastodon Project.” Over a period of a few months scientists dug trenches and pits to characterize the geology of the region and the collected thousands of fossils before excavators completed the reservoir construction and allowed the site to be flooded.

Location of Snowmass ski village (orange arrow), Colorado just north of Aspen and the high peaks of the Colorado Rockies. The Colorado River lies just to the north. Map from Google Maps, Google Inc.
Ziegler Reservoir at Snowmass showing how the site of this ancient lake sits nearly on top of a mountain ridge. From Pigati et al. 2014 (see references)

In that short period of time they collected several thousand bones of extinct megafauna—elephants, sloths, bears, camels, horses, bison, wolves, sheep, and deer.  I was drawn to the research at this location primarily because of my recent interest in proboscideans, or as I will call them more generally here: elephants. It is the extinct elephants that this Snowmass fossils site is best known for, hence the name: “Snowmastodon.” Mastodons were represented in the collection by over 3000 bones, representing at least 35 individuals. They also collected bones from four Columbian mammoths which are a distant cousin of the mastodon. The collection area represented only a small portion of the original lake basin. Hence, the bones recovered probably only represent a small portion of the individuals that are preserved at this site. From the number of individuals represented by their bones and the distribution of those individuals in multiple layers of sediments in the lake we can confidently infer that many elephants must have lived in this region as a community for many generations.

In addition to the megafauna remains collected in this ancient lake, over 26,000 bones from at least 40 additional  species of smaller vertebrate animals were recovered including snakes, otters, rabbits, beavers, frogs and salamanders. They also collected thousands of plant samples, including wood pieces, shells and other planktonic organisms.

In situ cosmogenic beryllium 10 and aluminum 26, optical stimulated luminescence (OSL), radiocarbon (14C)*, and uranium-series disequilibrium dating were were all performed to establish a chronology of the distinguishable layers of sediments in the ancient lake basin. Taking those dates and by mapping the locations, depths and types of sediments each fossil was found in, paleontologists were able to reconstruct how the environment at this location changed over tens of thousands of years and how the community of organisms that lived in and around this lake changed over that same time. This paleoreconstruction of the history of this lake provides an opportunity to test and compare predictions of past environments made from other locations using similar datasets.

Generalized stratigraphic diagram of the Ziegler Reservoir during excavation. Figure 4 from Miller et. al. 2014 (see references)

A temporal paleoreconstruction of a high alpine lake

The authors’ (see references below) reconstruction of the paleoenvironment of this lake and its surroundings begins with the lake’s origins more than 140,000 years ago. At that time a massive glacier produced by the Illinoian Ice Age filled the valley below the ridge that this lake is now found on top of. That glacier grew so large it overtopped the ridge and left a small moraine—the rocky rubble left when the ice melts leaving the rocks that were in the ice in a pile—on the side of the ridge and a small lake became impounded between the ridge and the moraine. This lake was originally about 30 feet deep.

Pollen and other plant and microorganisms preserved in the sediments reveal that soon after the lake’s formation, the environment warmed considerably, the moraine became forested and animals lived around this lake. Gradually but consistently for some 50,000 to 75,000 years, the lake filled with sediments—mostly from dust blown from the mountains and organic material falling into and growing in the waters of the lake. The fossil evidence suggests that once the lake waters became more shallow it transformed into a bog and wetland that was flooded at times (see figure below) and then eventually became an alpine meadow after 55 thousand years ago. That meadow has persisted from that time (including through the most recent Ice Age—the Wisconsin Ice Age) until the present.

General time line for the formation and filling of this ancient lake. Figure 11 from Pigati et al. 2014 (see references)

During most of the ancient lake and bog’s lifetime animals took up residence, for at least part of the year, along the margins of the lake where periodically individuals died and their bones were preserved in the lake or bog. By the time the lake had transitioned to a meadow about 55,000 years ago, the preserved vegetation record reveals that the region had become much colder than it is today. This colder period correlates with the Wisconsin Ice Age that was affecting most of North America. By this time the lack of megafauna fossils suggests that most of the megafauna were no longer present in the region though Woolly Mammoths may have persisted up until 50,000 years before present.

A problem of megafauna size for young earth creationists

I have presented a brief overview of the consensus view of the history of the snowmastodon fossil site in Colorado. In the next two posts we will use the observations above and explore additional details to demonstrate the monumental task that young earth creationists face as they attempt to interpret this evidence within their highly compressed timeline of earth’s history. For those not familiar, young-earth creationists presume a literal interpretation of Genesis requires that the Earth was created less than 10,000 years ago and that a global catastrophic flood destroyed all breathing land-living animals just 4350 years ago. Though not explicity recorded in Scripture, they are convinced that the earth has experienced a colder climate but they insist there was only a single Ice Age that reached its maximum extent just 4000 years ago.

Given these convictions and assertions, young-earth creationists (YECs) find themselves in the position of having to provide radically different alternatives to conventional scientific understandings of things such as: 1) the origins of the global biogeographic distribution of animal species (e.g. kangaroos in Australia, giant sloths in South America, Mastodons in Colorado, etc.), 2) how thousands of new species formed within hundreds or a few thousand years following departure of common ancestors on Noah’s Ark (i.e. rapid post-flood evolution), 3) how billions of fossils of ostensibly post-flood species that have gone extinct have been preserved without the aid of rapid burial via a global flood, and 4) why they are convinced by historical evidence there has been a recent Ice Age but are unwilling to consider the same forms of evidence that suggests that there have been multiple Ice Ages in Earth’s history.

Over the next two posts I will pose a series of questions related to the challenges listed above along with possible YEC responses, and assess the merits of those responses.

Coming up…

Can YECs find the Time After the Flood to Explain the Origins of a Ancient Fossil Lake Filled with Elephant Bones?
The Elephants in the Room: Migrating from Noah’s Ark


*Radiocarbon dating was performed on some bones found at the site but all samples yielded no radiocarbon above trace amounts indicative of samples that are more than 50,000 years old.  Therefore a number of additional dating methods were employed which are capable of dating objects older than 50,000 years.  As we will see this is relevant because bones that have been preserved in the most recent Ice Age have radiocarbon dates less than 50,000 years.   YECs only believe in a single Ice Age so the fact that these bones do not have radiocarbon in them would not be expected in the YEC understanding of earth history.

Literature used in preparation of this article:

Miller, Ian M., Jeffrey S. Pigati, R. Scott Anderson, Kirk R. Johnson, Shannon A. Mahan, Thomas A. Ager, Richard G. Baker et al. “Summary of the Snowmastodon Project Special Volume: A high-elevation, multi-proxy biotic and environmental record of MIS 6–4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA.” Quaternary Research 82, no. 3 (2014): 618-634.

Pigati, Jeffrey S., Ian M. Miller, Kirk R. Johnson, Jeffrey S. Honke, Paul E. Carrara, Daniel R. Muhs, Gary Skipp, and Bruce Bryant. “Geologic setting and stratigraphy of the Ziegler Reservoir fossil site, Snowmass Village, Colorado.” Quaternary Research 82, no. 3 (2014): 477-489.

Mahan, Shannon A., Harrison J. Gray, Jeffrey S. Pigati, Jim Wilson, Nathaniel A. Lifton, James B. Paces, and Maarten Blaauw. “A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado.” Quaternary Research 82, no. 3 (2014): 490-503.

Fisher, Daniel C., Michael D. Cherney, Cody Newton, Adam N. Rountrey, Zachary T. Calamari, Richard K. Stucky, Carol Lucking, and Lesley Petrie. “Taxonomic overview and tusk growth analyses of Ziegler Reservoir proboscideans.” Quaternary Research 82, no. 3 (2014): 518-532.

Strickland, Laura E., Richard G. Baker, Robert S. Thompson, and Dane M. Miller. “Last interglacial plant macrofossils and climates from Ziegler Reservoir, Snowmass Village, Colorado, USA.” Quaternary Research 82, no. 3 (2014): 553-566.

Miller, Ian M., and Mitchell A. Plummer. “A high-elevation, multi-proxy biotic and environmental record of MIS 6–4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA.” Quaternary Research (New York) 82, no. INL/JOU-14-33813 2014.

Wikepidia entry for the Snowmastodon Project:  

Full collection of research papers published about this site:  

Cover image: Paleoreconstruction of an ancient alpine lake. Denver Museum of Nature & Science.
Editing provided by LC

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