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.