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Canyonlands National Park Seedling in Biological Soil Crust
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Canyonlands National Park
Morrison Formation
photo: Dinosaur fossil in the Morrison Formation, Dinosaur National Monument
Dinosaur fossil in the Morrison Formation, Dinosaur National Monument
 

The Morrison Formation is composed of three members (listed from youngest to oldest): Brushy Basin, Salt Wash and Tidwell. Each has different characteristics due to changes in the depositional environment. This layer does not occur in Canyonlands.

Deposited
Late Jurassic (144 to 208 million years ago)

Depositional Environment
Varied between river, tidal flat and shallow marine

Appearance
Brushy Basin: multicolored Bentonite clays (volcanic ash)
Salt Wash: Light-colored, ledge-forming sandstone.
Tidwell: red marine sandstones frequently containing chert.

Notes
The Salt Wash Member is a source of Uranium which was mined throughout the Moab area. Dinosaur tracks and fossils also appear in the Morrison Formation.

Example
Visible in the northern parts of Arches (Salt Valley) and along Highway 191 north of Moab.

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Last Updated: July 01, 2011 at 10:07 MST