Geology at James M Robb - Colorado River
The Colorado River cut through Cretaceous sandstone and shale formations in the upper one-third of the corridor; those exposed at Island Acres include Mancos shale and the Mesa Verde group, sandstone and coal layers of the Mount Garfield, Sego Sandstone and Hunter Canyon Formations.
Tertiary sandstone, siltstone and shales of the Wasatch and Ohio Creek formations are exposed along the Book Cliffs. Landslides are common in this area, leaving debris below cliffs that is eroded, carried down-river and redeposited across the floodplain.
The spectacular Navajo and Mesa Verde sandstone formations of Colorado National Monument are highly visible from all parts of the Fruita section.