 |
|
 |

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 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.
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.
|
|
 |