million years ago (Late Cretaceous)
Find the clickable
hot spots for details and evidence, or follow the links below. (Click
to see larger image)
Colorado is literally at the bottom of the seanot
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.
- Rooney Road
near Dinosaur Ridge
- Garden of
the Gods Park and Visitor Center
Creek Nature Center
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.