The Laramide Orogeny in Mexico: An Updated Revision

Different styles of Laramide deformation present in the Mexican part of the North American Cordillera, as well as their spatial and temporal distribution, are succinctly described in this work. Contrasting characteristics in styles and deformational mechanisms are observed in northwestern, northeastern, and southern Mexico suggesting that mechanical heterogeneity of the lithosphere played an important role in transferring and accommodating deformation. In northwestern and mainly in southwestern Mexico, thick-skin tectonics is suggested by the vertical uplift of basement blocks; whereas in eastern Mexico, thin-skin deformation along multiple decollement surfaces predominates. In Sonora and Sinaloa, major boundaries of basement blocks appear to run E-W, whereas in southern Mexico, they are oriented N-S. Recent structural data suggest also that the geometry of important features in northeastern Mexico, such as the Monterrey curvature, are influenced by basement inversion during the late stages of deformation as well as the Sabinas basin (e.g., San Marcos Fault). The temporal distribution of magmatic activity in the past 140 Ma is a key element to date the deformation pulses and to infer the interactions between the plates in the Pacific basin and the western portion of the United States and northern Mexico. Based on this and using information derived from studies on active orogenic belts, the hypotheses proposed previously on the origin of the Laramide deformation (i.e. horizontal compression vs. vertical tectonics) are analyzed. Our observations confirm that the Laramide orogen in Mexico is far from being a sequential and progressive eastward deformation, and that any model explaining its origin must take into account the mechanical heterogeneity of the Mexican continental lithosphere.