New Mexico Geological Society Annual Spring Meeting — Abstracts

Triassic strata of eastern New Mexico and west Texas have long been identified as the Dockum Group. Recently, use of the term Dockum Group has been abandoned in eastern New Mexico, and instead a variety of new stratigraphic terms have been proposed for these strata. However, physical tracing of the beds in outcrop, petrographic study, and paleocurrent analysis indicate that the Triassic strata in eastern New Mexico are identical to those in west Texas. Contrary to opinions expressed by others, the term Dockum Group is properly defined and should be retained for these strata. The Triassic strata in west Texas and eastern New Mexico are contiguous in exposure, and do not occupy separate depocenters. The Santa Rosa Sandstone of New Mexico is present in the Canadian River valley and northern caprock escarpment of west Texas. These strata were formerly identified as the basal sandstone of the Tecovas Formation in Texas. Recent use of the term Camp Springs Conglomerate for the basal sandstone of the Tecovas Formation is incorrect. The Camp Springs Conglomerate is identical to the previously named Trujillo Formation. The Tecovas Formation is the same unit as that recently named the Garita Creek Formation in New Mexico. The name Tecovas Formation has clear priority, and the name Garita Creek Formation should be abandoned. The Trujillo Formation can be recognized throughout west Texas, the Canadian River valley, and the Pecos River valley in New Mexico. Overlying the Trujillo is a unit recently named the Bull Canyon Formation, however, the same strata were previously given the name Cooper Member (now formation). The name Bull Canyon Formation should be abandoned. The highest unit in the Dockum Group, the Redonda Formation, is only exposed in New Mexico. Together, the Santa Rosa, Tecovas, Trujillo, Cooper, and Redonda formations comprise the Dockum Group. All units except the Redonda can be recognized in the type area of the Dockum. The Dockum Group is equivalent to, but should be separated from, the Chinle Group of the Colorado Plateau. The Dockum Group occupies a depocenter discrete from the Chinle, and has a different provenance. Moreover, the term Dockum (1890) has priority over Chinle (1917). Dockum Group unconformably overlies older Triassic strata of the Anton Chico Formation in New Mexico and its equivalent in Texas, or Permian strata. The Dockum Group is unconformably overlain by Jurassic and younger strata.