[1] The formation also records the progressive unroofing of nearby mountainous uplifts during the Laramide orogeny.

The formation consists of interbedded gray to red sandstone and mudstone with minor conglomerate with a total thickness of 730 meters (2,400 ft).

[2] In the vicinity of Sierra Blanca, the formation is intruded by dikes with K-Ar ages of 47.7 +/-2.9 Ma (million years ago).

The composition of the upper beds records progressive unroofing of nearby mountainous uplifts during the Laramide orogeny, with decreasing amounts of sandstone fragments and increasing amounts of basement rock fragments.

[4] Spencer G. Lucas and his coinvestigators disagreed on the basis of fossil evidence, placing the formation in the Eocene.