Triassic of West Texas

The Dockum series, of Upper Triassic age, overlies much of the oil-producing area in the southern part of the Permian basin, in West Texas and southeastern New Mexico. In the area south of the 33d parallel the Dockum consists of red and non-red conglomerate, sandstone, and shale beds of terrestrial origin. An examination of the series in well samples shows that it is composed of two formations. The names Santa Rosa and Chinle, as used for the Triassic of central New Mexico, are extended to include the equivalent formations in the Texas section. A critical study of the means used for separating the Red-beds of the Triassic and Permian shows that the gravel and non-lithified shales of the Triassic and the thick beds of very fine sandstone and hard shale of the Permian are t e most prominent features.