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Abstract: The Saga of the Dockum Group and the Case of the Texas/New Mexico Boundary Fault

Thomas M. Lehman

The Upper Triassic Dockum Group consists of continental red beds exposed around the southern High Plains of western Texas and eastern New Mexico. Although these strata are contiguous between the two states, different stratigraphic nomenclature is used in Texas and New Mexico. New mapping of the type area in Texas and physical tracing into New Mexico allow recognition of five units in the Dockum Group. A distinctive quartzose conglomeratic sandstone, the Santa Rosa Sandstone, is recognized as the base of the Dockum Group in New Mexico. The informal name "Camp Spring conglomerate" should not be used for this same unit in Texas. The Santa Rosa Sandstone is overlain by multicolored shale of the Tecovas Formation in Texas. The name "Garita Creek formation" should not be used for these same strata in New Mexico. The Tecovas Formation is overlain by cliff-forming lithic sandstone of the Trujillo sandstone. The same unit was later named the "Cuervo sandstone" in New Mexico. Overlying the Trujillo sandstone is a thick sequence of red shale called the Cooper Canyon formation in Texas. These same strata were given the name "Bull Canyon formation" in New Mexico. The Redonda Formation comprises the uppermost unit in the Dockum Group, and it is only present in New Mexico. Use of the name "Chinle formation" or "Chinle group" for part or all of these strata in eastern New Mexico is not appropriate, and ignores the fact that formal names had previously been given to these strata in Texas.

"Stratigraphy can be defined as the complete triumph of terminology over facts and common sense" (attributed to P. D. Krynine by J. Ferm in Burton et al., 1987).

AAPG Search and Discovery Article #90980©1994 AAPG Southwest Section Meeting, Ruidoso, New Mexico, April 24-26, 1994