Límites temporales de la deformación por acortamiento Laramide en el centro de México

Abstract

In central and northern Mexico, sets of rocks deformed by shortening between the Late Cretaceous and early Cenozoic have been considered the result of the Laramide orogeny. This orogeny is mentioned when reference is made to the sedimentary sequences of central, eastern and southern Mexico. The “Laramide deformation” is the youngest shortening event, because the only recognized overprinted tectonic structures are associated with lateral an extensional events. The main objective of this study is to establish the temporal evolution of shortening deformation related to the Laramide orogeny in central Mexico, on the basis of geochronological data (U/Pb in zircon) and (40Ar/39Ar in biotite and muscovite) from pre-, syn-, and post-deformation units. Additionally, structural levels and metamorphic facies were determined in the study regions. The main effects of the Laramide deformation are shortening, uplift and metamorphism, gravitational collapse and exhumation. The event began between ca. 105 Ma in the west and culminated at ca. 55 Ma in the east. Likewise the variation in the lifetime of the deformation event of ca. 20 m.y. in the west, and ca. 4 m.y. in the east is documented, in the zone where the shortening was established.