Dinosaur track site in Alaska reveals remarkable details of the past

A team of researchers from the University of Alaska Fairbanks (UAF) has recently unveiled what is possibly Alaska’s largest single dinosaur track site. Nestled in the Denali National Park and Preserve, this remarkable location has been called “The Coliseum” by the scholars.

Spanning an area akin to one-and-a-half football fields, The Coliseum boasts numerous footprints immortalized in rock. This extensive site provides a snapshot of various dinosaur species that roamed what is now Interior Alaska approximately 70 million years ago. 

Walking back in time

“It’s not just one level of rock with tracks on it,” said lead author Dustin Stewart, who conducted this research during his graduate studies in Paleontology at UAF. “It is a sequence through time. Up until now, Denali had other track sites that are known, but nothing of this magnitude.”

To the untrained eye, amidst the vast terrain of the park, this site might appear to be just another multi-layered rocky rise, stretching over 20 stories. But as the experts soon discovered, its significance ran deeper.

“When our colleagues first visited the site, they saw a dinosaur trackway at the base of this massive cliff. When we first went out there, we didn’t see much either,” said senior author Pat Drukenmiller, a curator of the University of Alaska Museum of the North.

Bringing the footprints to light

Upon Stewart’s first visit, after a strenuous seven-hour hike, the track site seemed unimpressive. But as twilight descended and the sunlight hit the rocks just right, a revelation occurred.

“When the sun angles itself perfectly with those beds, they just blow up,” he reported. “Immediately all of us were just flabbergasted, and then Pat said, ‘Get your camera.’ We were freaking out.”

Back in the Late Cretaceous Period (100.5 to 66 million years ago), the cliffs that form The Coliseum were sediment layers near what was most likely a communal watering spot on an expansive floodplain. Earth’s tectonic movements over time caused these flat layers to dramatically shift and stand vertically, bringing the footprints to light.

Remarkable details 

These tracks consist of both fossilized impressions from ancient times and casts formed when sediment filled in these depressions and solidified. “They are beautiful. You can see the shape of the toes and the texture of the skin,” Druckenmiller said.

The site also offered additional findings like ancient plant fossils, preserved pollen, and evidence of ancient freshwater mollusks and invertebrates. According to Stewart, all of these little clues can help us reconstruct what the environment looked like as a whole during that period. 

A dinosaur hotspot

The region was part of a vast river network, with adjacent ponds and lakes. The area’s climate was significantly warmer, reminiscent of today’s Pacific Northwest. Tall coniferous and deciduous trees stood tall, with a dense underbrush of ferns and horsetails.

The footprints suggest that the region was a hub for a wide variety of juvenile and adult dinosaurs that frequented the place over thousands of years. Although herbivorous duck-billed and horned dinosaurs were the most common types of dinosaurs treading these grounds, traces of carnivores like raptors, tyrannosaurs, and some aquatic birds were also documented.

“It’s amazing to know that around 70 million years ago, Denali was equally impressive for its flora and fauna,” Druckenmiller said.

Balancing conservation and exploration

Denny Capps, the park’s geologist, underlined the balance between conservation and exploration. “On one hand, we must protect world-class fossil sites like The Coliseum from disturbance and theft,” he stated. “On the other hand, we encourage visitors to explore for fossils in their geologic context to better grasp the evolution of landscapes and ecosystems through time, while leaving them undisturbed for others to appreciate.”

In future research, Druckenmiller is keen on deepening his collaboration with the National Park Service to further study The Coliseum and similar sites. “Our track research in the park compliments our work on dinosaur bones we collect in northern Alaska, along the Colville River. Denali National Park and Preserve is a world-class area for dinosaur tracks. There is a lifetime of exploring left to do, and I can only wonder what other surprises await.” he concluded.

The study is published in the journal Historical Biology. 

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By Andrei Ionescu, Earth.com Staff Writer

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