Guadalupe to Boquillas: A 250-Mile Fault Zone (Trans-Pecos Rift?)

Bruce Pearson

From north of the New Mexico-Texas border west of the Guadalupe Mountains southeast to Boquillas, Mexico, on the Rio Grande is a series of fault-bounded basins or grabens: Salt basin, Valentine basin, Marfa basin, and Tornillo basin. Each basin has its own special character, but all are related to the same fault system--one which may be as much as 300 mi long. The Valentine and Marfa basins in the central part of the trend are covered with Tertiary volcanic flows and continental deposits, so the structural outlines of these two basins and their continuity with the others are not obvious at the surface.

Questions that need to be answered are: (1) how this fault zone relates to older regional structural elements of the Texas craton (Precambrian), Diablo platform (Permian), and Coahuila platform (Mesozoic); (2) which type of lateral and extensional displacement occurred, particularly as the result of Laramide and late Tertiary deformation; and (3) is this a rift or a basin-and-range structural system.

AAPG Search and Discovery Article #91034©1988 AAPG Southwest Section, El Paso, Texas, 21-23 February 1988.