Dinosaur discovery reveals ancient Alaska's warm, lush landscape

In the remote expanse of northwestern Alaska, the discovery of ancient dinosaur tracks, alongside fossilized plants and tree stumps, has offered unprecedented insights into the lush and wet environments of prehistoric era when dinosaurs freely roamed between Asia and North America.

This significant find dates back approximately 100 million years ago. It illuminates new aspects of the climate and animal migration patterns of that era. This discovery provides a clearer picture of the ancient world that once existed in this region.

The study was led by Anthony Fiorillo from SMU and Paul McCarthy of University of Alaska Fairbanks (UAF), and UAF graduate student Eric Orphys, was published in the journal Geosciences.

Unraveling Alaska’s ancient climate secrets

For over two decades, Fiorillo and McCarthy have explored Alaska’s prehistoric landscapes. They have been striving to integrate geological and paleontological data to reconstruct ancient climates.

“We’ve had projects for the last 20 years in Alaska trying to integrate sedimentology, dinosaur paleontology and the paleoclimate indicators,” McCarthy said. “We’ve done work in three other formations — in Denali, on the North Slope and in Southwest Alaska — and they’re about 70 million years old.”

Bering Land Bridge and the Nanushuk Formation

Their recent focus on the Nanushuk Formation has unveiled fascinating details about the Cretaceous period. This includes insights into the Bering Land Bridge, which served as a vital connection between the continents.

Fiorillo, who now works at New Mexico Museum of Natural History and Science, highlighted the significance of this era in ancient Alaska.

“What interested us about looking at rocks of this age is this is roughly the time that people think of as the beginning of the Bering Land Bridge — the connection between Asia and North America,” he said. “We want to know who was using it, how they were using it and what the conditions were like.”

Their research provides insights into contemporary climate change. According to the team, studying ancient climates helps us comprehend the challenges of our warming planet.

“The mid-Cretaceous was the hottest point in the Cretaceous,” McCarthy noted. “The Nanushuk Formation gives us a snapshot of what a high-latitude ecosystem looks like on a warmer Earth.”

Treasure trove of prehistoric life

The Nanushuk Formation spans the central and western North Slope and is a rich source of evidence. It dates back to the mid-Cretaceous, around the time when the Bering Land Bridge first emerged.

Fieldwork conducted between 2015 and 2017 in the Coke Basin area revealed about 75 fossil tracks. These findings and other remnants indicate a vibrant, riverine ecosystem in ancient Alaska.

Their findings included diverse dinosaur tracks and numerous fossilized tree stumps, some measuring up to 2 feet in diameter. This painted a vivid picture of a lush, prehistoric environment. The researchers’ analysis of these tracks revealed a predominance of bipedal plant-eating dinosaurs. These constituted 59% of the total tracks found.

Moreover, the abundance of bird tracks unearthed suggests the warm paleoclimate of the area may have attracted avian species during the Cretaceous. This role mirrors how it attracts North America’s shorebirds today.

“We were at a spot where we eventually realized that for at least 400 yards we were walking on an ancient landscape,” Fiorillo said. “On that landscape we found large upright trees with little trees in between and leaves on the ground. We had tracks on the ground and fossilized feces.”

Ancient Alaska was wet, warm and lush

Through carbon isotope analysis of wood samples, the team determined that the region received approximately 70 inches of annual precipitation. This supports the theory of a significantly warmer and wetter climate during the mid-Cretaceous compared to present-day conditions.

Fiorillo likened the ancient climate to modern-day Miami, highlighting the significant differences in temperature and rainfall.

“The temperature was much warmer than it is today, and what’s possibly more interesting is that it rained a lot,” Fiorillo said. “The samples we analyzed indicate it was roughly equivalent to modern-day Miami. That’s pretty substantial.”

Environmental implications and future study

McCarthy’s expertise in fossil soils allowed the team to reconstruct the ancient landscape of Alaska. They identified river channels, flood deposits, and other environmental features. These features provided a habitat for diverse dinosaur species.

“We can say here’s a river channel, here’s a flood deposit, here’s a levee, here’s the floodplain, here’s a swamp,” McCarthy said. “And so if we’re able to find tracks in that section, then you can sometimes say that a group of dinosaurs seems to have really liked being here as opposed to there.”

Fiorillo insists that there’s much more work to be done. “This puts a new dot on the map and tells us there’s a lot here, and it fits into the bigger picture,” he concluded. “The big picture is we’re trying to get better resolution on what life was like in the high latitudes back at the time the dinosaurs were roaming around.”

Modern climate lessons learned from ancient Alaska

This important work by Fiorillo, McCarthy and their team in northwestern Alaska unveils a captivating glimpse into the prehistoric world, bridging the gap between past and present climates.

By uncovering a trove of dinosaur tracks, fossilized plants, and evidence of a rich ecosystem dating back 100 million years, the study enriches our understanding of the Earth’s geological history and offers valuable insights into the effects of climate change.

The findings from the Nanushuk Formation highlight the dynamic interplay between flora, fauna, and climate during the mid-Cretaceous period, underscoring the importance of continued exploration and study to fully grasp the complexities of our planet’s past and its implications for our future.

The full study was published in the journal Geosciences.

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