Stratigraphy of the Paleogene Chuska Sandstone, New Mexico-Arizona
— Spencer G. Lucas and Steven M. Cather

The Chuska Sandstone is a Paleogene, sandstone-dominated stratigraphic unit exposed along and around the crest of the Chuska Mountains in Arizona-New Mexico. The Chuska Sandstone consists of two members. The lower Deza Member is fl uviatile in origin, as much as 81 m thick, and consists of ripple-laminated, trough-crossbedded and massive arkosic sandstone with signifi cant interbeds of siltstone and claystone. The upper Narbona Pass Member, up to 535 m thick, is almost exclusively crossbedded arkosic sandstone of eolian origin. The only fossils known from the Chuska Sandstone are shell fragments of emydid turtles in the Deza Member that are indicative of perennial water, but, with an emydid stratigraphic range of Eocene-Recent, they are of little biostratigraphic signifi cance. Radioisotopic data indicate that deposition of the Chuska Sandstone began ~35 Ma (late Eocene) and ended in the early Oligocene.