The cliff-forming rocks seen here are eolian sandstones in Dinosaur National Monument, Utah. The unit is locally called the Glen Canyon Sandstone, but it's equivalent to the Navajo Sandstone (elsewhere, it's called the Nugget Sandstone). The Navajo/Nugget/Glen Canyon is a thick quartzose sandstone succession with abundant cross-bedding. Cross-bedding refers to tilted layers between horizontal layers, and forms in a one-directional current by wind or water (in this case, wind). The sandstone is part of a sand dune deposit in an ancient, vast desert, or "sand sea", technically called an "erg".

The reddish-colored, partly vegetated slopes below the Glen Canyon are part of the Upper Triassic Chinle Formation, a multicolored, nonmarine unit consisting of coarse-grained siliciclastics (fluvial channel facies) and fine-grained siliciclastics (floodplain facies). Quartz-permineralized fossil wood is famously common in the Chinle Formation (for example, at Petrified Forest National Park in Arizona).

Stratigraphy: Glen Canyon Sandstone (Upper Triassic-Lower Jurassic) over Chinle Formation (Upper Triassic)

Locality: outcrop near Cub Creek Road, Dinosaur National Monument, northern Uintah County, northeastern Utah, USA

See info. at: <a href="https://en.wikipedia.org/wiki/Dinosaur_National_Monument" rel="noreferrer nofollow">en.wikipedia.org/wiki/Dinosaur_National_Monument</a>

Geologic map of Dinosaur National Monument: