Stratigraphic Controls on the Structural Evolution of the Sierra Madre Oriental Fold-thrust Belt, Eastern Mexico
Wolfe, Zachary 1978-
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Late Cretaceous–Paleogene Laramide shortening within the Sierra Madre Oriental fold-thrust belt (SMO) along the western margin of the Gulf of Mexico is the product of shallow subduction of the Farallon plate beneath the western margin of Mexico. Changes in detachment strengths during this thin-skinned shortening episode created alternating salient and recesses along the 1500-km strike of the SMO that include the ~200-km-long Potosi recess located southwest of the city of Ciudad Victoria. I propose that the observed orogenic curvature of the SMO is controlled by evaporite remobilization by the Laramide thrust detachment evaporates. Salients of the SMO are underlain by evaporates while areas like the Potosi recess lack underlying evaporites. In addition to these stratigraphic controls of the SMO, the linear frontal thrusts of SMO were influenced by inversion of a linear, pre-existing rift of Jurassic age and by thrusting of weak Upper Cretaceous shales. In this study I used previously published geologic maps, well data, and new interpretations of satellite and magnetic data to provide insights into the formation of the Potosi recess. Results of this study include the following: 1) Frontal thrusts along the leading edge of SMO dominantly occur along weak Upper Cretaceous shales and are located above a partially inverted and linear Jurassic rift system related to the opening of the Gulf of Mexico; 2) Salients north and south of the Potosi recess are controlled by the presence of two salt bodies known from well data compiled in this thesis; 3) Topographic variation and previous thermochronologic studies along the leading edge of the SMO suggest that a late stage (30-40 Ma), thick-skinned Laramide event inverted the Jurassic rift system at differing amounts along its strike.