The Conservancy has acquired the Sunset Ranch Petroglyphs, which are located thirty miles southeast of El Paso and a few miles north of the Mexican border in west Texas. Developer Alan Erickson has donated over 300 acres in four lots ranging in size from twenty to 120 acres, all of which are within a 300-square-mile rural subdivision. These lots contain tens of thousands of petroglyphs that are concentrated on huge boulders scattered along the slopes of a series of mesas that are part of an eroding formation of Cox Sandstone.
The mesas were formed from marine sediments when most of West Texas was covered by a shallow sea during the Early Cretaceous period more than 100 million years ago. As rain, sunlight, and oxygen interact with minerals in the stone over time, the light brown sandstone surfaces of the boulders oxidize, creating a thin dark patina on the exposed exterior surfaces that serve as a blank canvas for a petroglyph gallery. The patina covering the rock was carefully pecked away with a harder stone, exposing the unoxidized buff color of the sandstone underneath to create the petroglyphs. The images range from geometric to zoomorphic to anthropomorphic forms, and they have been stylistically associated with rock art images at sites in the region that date to the Archaic and Formative periods.