Structure and Tectonics of the Sierra Madre Oriental Fold-Thrust Belt Near Monterrey, Northeastern Mexico

Abstract

The Monterrey salient was examined using Landsat TM and MSS images to determine factors controlling the development, distribution, and exposure of Laramide structures. Lateral Mesozoic facies changes influence structural styles and distribution. Exposure of deep foreland structures north of Monterrey is partly related to the location of the Cupido reef trend. Structure along the front of the salient changes abruptly from tectonic wedging to normal overthrusting where deltaic clastics of the Difunta Group grade into incompetent Mendez shale. Salt thickness is an important factor controlling structural development. Areas without evaporites are usually persistent basement highs characterized by less severe deformation. Areas with thin evaporites have complex structural styles, depending on stratigraphy, depth of exposure, and distance from the Sierra Madre thrust front. Thick salt, apparently in a Jurassic rift beneath the salient, facilitated the northward transport of thrust sheets. Late Cretaceous salt movement influenced stratigraphy in La Popa basin where limestone lenses developed in the clastic Difunta Group. Basement topography is the major factor controlling development, style, distribution of structures, and areal distribution of salt and lateral facies changes. The authors propose a tectonic model that explains the large scale structural styles in the region. The Coahuila basement-high block actedmore » as a buttress during Laramide shortening, limiting northward progression of deformation west of Saltillo. East, in the Monterrey salient, the effect of deeper basement and thick salt permitted thrusts to transport material much farther north, resulting in development of a north-south zone of distributed left-lateral shear in the region of Saltillo.« less