Abstract: Paleogeography, Mechanical Stratigraphy, and Deformation Styles in the Sierra Madre Oriental, Mexico

PROST, GARY, RANDALL MARRETT, JAVIER MENESES, ; MARIO ARANDA, SALVADOR ORTUNO

The Sierra Madre Oriental (SMO) fold-thrust belt extends from northwest of Torreon to south of Veracruz, Mexico. Development of the Laramide-age SMO can best be understood using a critical-wedge model recognizing that the strength of the decollement controls the geometry of the mountain front, the deformation style of the thrust sheets, and the variation in shortening across the fold belt.

Movement vectors derived from field observations in the SMO suggest a regional northeast-directed tectonic transport, but change to perpendicular to the mountain front as one nears the foreland. Shortening typically is about 50% above clastic or carbonate decollements and about 30% above evaporite decollements.

Paleogeography had a significant influence on the development of the SMO. The basin of the "Mar Mexicano" accumulated Upper Jurassic evaporites that played a major role in the deformation of the SMO. Lower Cretaceous platform evaporites also affected deformation style.

Structural styles vary dramatically along the SMO, depending on the lithology of the dominant decollement. Evaporite decollements are typically associated with large upright, tight to isoclinal box or fan folds with no preferred vergence and few emergent thrusts. Deformation produced imbricate thrusting, fault-bend and fault-propagation folds that verge toward the foreland in areas with detachment in clastic, carbonate, or metamorphic rocks.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria