Deformation History of the Sierra Madre Oriental, Mexico, and Associated Hydrocarbon Generation-Preservation

Mario Aranda, D. F. Gary Prost, Randall Marrett, Samuel Eguiluz, Jose G. Galicia, Javier Banda, Jaime Patino

The Sierra Madre Oriental fold and thrust belt is a single large salient about 600 km wide between Torreon, Coahuila and Tamazunchale, San Luis Potosi. It projects into the foreland a maximum of 250 km near Monterrey, Nuevo Leon. Kinematic and paleomagnetic data together with field relationships suggest that the salient is best understood using a critical-wedge mechanics model recognizing that the distribution of evaporite decollements controls the map pattern of the Sierra Madre salient The critical-wedge model provides a coherent explanation incorporating the distribution of evaporites, the geometry of the mountain front, the style of the cover and basement deformation, the variation in shortening, and the position of the hinterland.

The Sierra Madre folded thrust belt developed during the Upper Cretaceous-Eocene Laramide Orogeny. Most structures are presently breached to the Cretaceous reservoir level, and some folds are breached to the Jurassic level Buried structures may exist intact at or below the northern and eastern mountain fronts (frontal thrusts) along the entire length of the Sierra Madre from Torreon to the trans-Mexican volcanic belt.

Most of the Sierra Madre Oriental appears to be in the gas window today and would have generated hydrocarbons prior to or during the Laramide deformational event However, source rock maturity appears to decrease near the mountain front in the southernmost part of the Sierra Madre, and it is possible that hydrocarbons were generated here after the Laramide. Unfortunately, most of the structures in this part of the mountains are deeply eroded.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995