This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Imagine the Western Plains of North America, from Texas to Alaska, submerged under a broad, shallow seaway. To the west lay the ancestral Rocky Mountains.
To the east were low-lying plains traversed by large, sluggish rivers. This was the landscape of North America in the mid-Cretaceous period—a geological age spanning 105–75 million years ago—when the global sea level was around 100 meters (328 feet) higher than it is now. A high concentration of atmospheric carbon dioxide, due to massive volcanism, created a "greenhouse" climate such that Earth lacked significant polar ice caps.
Alaska and Antarctica enjoyed temperate climates. The record of dinosaur bones and tracks from this time in North America is sparse, especially from the Coniacian age—a substage of this Cretaceous period spanning 89.75–86.5 million years ago. We have discovered the first Canadian dinosaur tracks from this Coniacian age in the Tumbler Ridge area of northeastern British Columbia.
One of us, Guy Plint, first noticed these tracks in 1988. However, the remote nature of the site, best accessed by helicopter, delayed further investigation until 2022, when we were able to begin a more comprehensive study together. The findings were recently published in Historical Biology.
North America has yielded an abundant record of dinosaurs, including both skeletal material and tracks. Because dinosaur tracks can only be made and preserved in nonmarine, terrestrial sediments, most North American tracks are found in sedimentary rocks laid down by rivers that drained the Rocky Mountains. Their sediment load gradually built deltas and coastal plains along the western margin of the Interior Seaway.
Over millions of years, sea level slowly rose and fell, alternately narrowing and widening the coastal plain. The late Cenomanian, Turonian, Coniacian and Santonian stages of the Cretaceous period—between about 95 and 84 million years ago—were times of exceptionally high sea levels, when shorelines were pushed westward, lapping against the foothills of the Rocky Mountains. In western Canada, Coniacian rocks are entirely marine, with the exception of the small Tumbler Ridge area of northeastern British Columbia.
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