Crossbedding in de Chelly Sandstone.

The de Chelly (de shay) sandstone is a unit with large-scale crossbedding, inferred to be of dune origin, like the Navajo Sandstone of Zion and Glen Canyon. It's considerably older, though, being Permian, some 150 million years or so before the late Jurassic. It forms both Canyon de Chelly and the buttes in Monument Valley. It's correlative with the Coconino Sandstone of the Grand Canyon.
On the trail to White House ruin.