Colorado Geology Through Time

In the Pennsylvanian period the Ancestral Rockies, Frontrangia and Uncompahgria, started to form. Rivers carried the sediments, consisting mostly of feldspar-rich gravels and sand that will be the source of red color of future rock reds, from the Ancestral Rockies and today we could see the deposits near the Red Rocks Park known as a Fountain Formation. Huge Lycophytes trees that reached up to 30 m (100 feet), ferns, and horsetails were the most common plants. Oxygen level reached 35% and it allowed invertebrates to reach enormous sizes. With more terrestrial landscape appeared in Pennsylvanian, reptiles evolved an amniotic egg which allowed to reproduce on land and explore more territories. 

End-Permian Mass Extinction vanished over 90% of all species on Earth. Stromatolites created by photosynthetic cyanobacteria formed layered mineral “microbial mats”.

In the Cretaceous Period, about 100 MA, Colorado was a coastline of the Western Interior Seaway, a large inland sea that split the continent into Laramidia and Appalachia. The Dakota Sandstone was deposited along this coast and preserved many plants and numerous of dinosaur tracks on the Cretaceous east side of Dinosaur Ridge. 

The Front Range of the Rocky Mountains had formed. Denver Formation was deposited during this time. This formation produce a great variety of vertebrate fossils such as Tyrannosaurus rex, Triceratops, Edmontosaurus, Pachycephalosaurus. Huge Triceratops tracks could be seen at the Dinosaur Ridge sites. 

By 64 million years ago, swampland had given way to a tropical rainforest in the Front Range, life emerged and Colorado was covered with tall trees and vines. An interesting mammal, wombat-looking Stylinodontine taeniodont (teeny-o-dont), was excavated from a Castle Rock Rainforest site along with enormous leaves and many plants. 

Dawson Arkose, multi-colored layers of clay, formed by 37 million years ago, today could be seen at the Paint Mines Interpretive Park. During this time a great volcanic eruption took place in the Collegiate Range and covered the landscape in molten hot ash that instantly torched and consumed everything across the landscape. Titanotheres, relatives to rhinos and horses, browsed the Colorado landscape. Later in time Florissant Formation formed, it produces petrified wood and the fossilized plants and animals.

In the latest Pleistocene Epoch during the Ice Age camels, mammoth and mastodon, horses and giant sloths lived in the grasslands of Highlands Ranch Open Space. Mount Evans, the highest peak in the Front Range of the Rocky Mountains of North America is seen behind the plain and pine forests. There were glaciers in the Rocky Mountain but not much ice in the Colorado.