This Permian Terrestrial deposit was formed as a dune eolian deposit, and exhibits the typical crossbedding and sandy texture of such deposits. With an age of 270 - 275 million years old, several very different lithologies are represented.
Fossils are very scarce in the redbeds, sometimes worm burrows and plant impressions can be found.
The Schnebly Hill formation is divided in two by the Fort Apache Limestone. This represents a marine transgression onto the dune fields for a short time period. The lowest member in the formation is called the Rancho Rojo member. This bright red sand wave deposit was formed when dune sands enter the marine enviorment by blowing wind. The resulting subsurface sand forms low rolling waves which have a unique lithology.