DMNS-Ancient Denvers

70 million years ago (Late Cretaceous)

Find the clickable hot spots for details and evidence, or follow the links below. (Click to see larger image)

Description: Colorado is literally at the bottom of the sea—not a mile high, but a tenth of a mile deep! The nearest shoreline is hundreds of miles to the west. Here and there, the surface of the water is broken by the spouts of air-breathing marine reptiles. In other places, schools of fish are chased to the surface, drawing the attention of soaring pterosaurs. But landing on the water can be dangerous in a sea full of sharks, toothy fish, and mighty marine lizards known as mosasaurs.

Formation: Pierre Shale

Artist: Donna Braginetz

Best Viewing Spots:

Rooney Road near Dinosaur Ridge
Garden of the Gods Park and Visitor Center
Fountain Creek Nature Center
Valmont Dike

The Pierre Shale is a relatively soft rock, so it rarely forms outcrops. This roadcut on Rooney Road south of Golden is a place where the Pierre Shale has been tilted from its original horizontal orientation to a nearly vertical position. You can see thin, resistant ledges of sand. When this was a muddy seafloor, the thin layers of sand were deposited during storms.

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