Westward-Vergent Thrusting in Northern Sierra de Pena Blanca, Chihuahua, Mexico

P. C. Goodell, R. Chavez A., I. Reyes C.

The Chihuahua trough was a major basinal feature in northern Mexico during the Mesozoic. Deformation of Mesozoic sediments during the Laramide orogeny occurred in Arizona, New Mexico, and west Texas on the eastern border of the trough. Where present, overthrusting is usually vergent to the northeast or east. Westward-vergent over-thrusting occurred on the western margin of the Chihuahua trough.

The northern Sierra de Pena Blanca is composed of Cretaceous sediments and two major sequences of Tertiary ash flow tuffs and their clastic derivatives. The lower of these sequences has been asymmetrically overthrusted to the west and is unconformably overlain by the younger sequence. This younger sequence is also present at the Pena Blanca uranium deposit several kilometers to the south.

Laramide compression is interpreted to have caused westward-vergent thrusting in the northern Sierra de Pena Blanca, against a more continental buttress to the west.

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