Structural evolution of the Sierra Madre Oriental fold-thrust belt, east central Mexico

Sierra Madre Oriental (SMO) fold-thrust belt is a northwest-southeast trending contractional belt that spans nearly the entire length of Mexico. The research is directed toward determining its structural style, kinematics, deformation sequence and tectonic setting. Field mapping, structural analysis and well data are used to provide insights into the structural architecture and the nature of the detachment underlying the SMO foldthrust belt. Deformation in the SMO is characterized by two phases of deformation: an early thin-skinned phase and a late thick-skinned phase. Structural windows and borehole data show that a dominant detachment occurs at the base of Jurassic Zuloaga Formation, and that eastward advance of the fold-thrust belt along the detachment was facilitated by two weak layers. One is evaporite of late Jurassic age (Minas Viejas Formation), and the other is Jurassic red beds (La Joya Formation). Shortening above the detachment is absorbed by a variety of structures that are genetically related to each other. Initial deformation in the cover sequence has been taken up by layer-parallel shortening. It is followed by detachment folding. With continued deformation, sedimentary rocks in pre-SMO rift basins were translated upward, and rift-related normal faults may have been reactivated as reverse faults.; Regional field mapping shows contrasting structural styles between the western (hinterland) and eastern (foreland) portions of the Sierra Madre Oriental fold-thrust belt. The eastern domain is characterized by intense deformation documented by large-displacement thrusts and folds with long wavelength and high amplitude. In contrast, the western domain is weakly deformed. Fold trains display short wavelength and low amplitude. The regional detachment surface at the base of the late Jurassic dips eastward toward the Gulf of Mexico basin during shortening. On this basis, it is proposed that a large portion of the Sierra Madre Oriental fold-thrust belt evolved as a gliding thin-skinned sheet moving down-slope eastward with shortening concentrated in the frontal region and low internal deformation in the hinterland. Two processes assisted in driving gravitational gliding, (1) uplift of the Sierra Madre Occidental and Mesa Central during the Late Cretaceous-early Cenozoic, and (2) Early to Late Cretaceous thermal subsidence along the western margin of the Gulf of Mexico.