“Bits and Pieces: Ice Age Fossils from Alberta” by: Dr. Chris Jass
One reason The Mammoth Site is exceptional is that many relatively complete skeletons are preserved at the Site. Few such Ice Age fossil localities are known! Most of the sites that we study contain sparse records characterized by fragments of Ice Age vertebrates. That is especially true in Alberta, where much of my fieldwork and research takes place.
In Alberta, the Ice Age fossil record that I study primarily consists of isolated and fragmentary remains that are found along major river drainages. Unlike The Mammoth Site, where so many animals died in one spot, in Alberta we find only scattered, isolated bone fragments that survived the environment of large river systems, which can be very destructive to animal remains and fossils. In a sense, finding Ice Age fossils in Alberta is akin to looking for needles in haystacks—the fossils are relatively rare compared to the volume of sand and gravel that they’re buried in. As a result, my research program at the Royal Alberta Museum works closely with the sand and gravel industry, because the industry’s mining of these geological resources is what uncovers many of the fossils that we study.
We view each fragmentary record that we recover as unique evidence of the Ice Age past. That is, each bit of mammoth, bison, horse, or other Ice Age animal has a unique story to tell. And collectively, those bits and pieces allow us to start piecing together a broader Ice Age history for the area.
We typically only find Ice Age fossils that either pre- or post-date the last major advance of continental ice sheets. Roughly 18,000 years ago, ice sheets advancing from northeastern Canada met up with ice sheets advancing out of the Canadian Rocky Mountains. So between roughly 22,000 years ago and 12,000 years ago, the ice sheets both directly and through their proximity rendered Alberta landscapes uninhabitable. In a sense, the glaciers “cleaned the slate”, and the plants and animals that we see today in Alberta represent an assemblage formed over only the last 12,000 years. That geologic history represents a stark contrast to southwestern South Dakota, where no record of great continental ice sheets exists, and The Mammoth Site represents a point along a continuously changing landscape.
In Alberta, we’ve looked at the abundance of fossils that occur in deposits that pre-date the last glacial advance and compared them to the abundance in “after-the-ice” deposits. Together, these data sets reveal interesting patterns in mammal assemblages in Alberta. During the time leading up to the last advance of continental ice, horses, mammoths, and bison were the most common large animals inhabiting central Alberta. Following the retreat of that ice, we see a significant change: fossils of horse and mammoth are less common relative to bison, meaning that after the ice sheets retreated bison became the most common large mammal on the landscape. In other words, Alberta changed from a horse-dominated landscape to a bison-dominated landscape in a relatively short period of geologic time.
Despite many challenges arising from the nature of the Ice Age fossil record in Alberta, we are slowly piecing together a story that reflects the unique geologic history of the province. Every bit and piece of the fossil record has a story to tell, either individually or collectively!