Stress pattern evolution in the central sector of the Mexican Volcanic Belt

Stratigraphic studies and detailed field analyses of brittle and plastic deformations allow the reconstruction of the stress pattern and the tectonic evolution of the central sector of the Mexican Volcanic Belt. Several compressional phases affected the metamorphic basement, while the last one also involved the volcanic cover of Early Miocene age. In Middle Miocene-Early Pliocene times and ENE-WSW extensional phase developed, representing the southern protraction of the Basin and Range Province of the western United States. In Pliocene-Quaternary times there then followed the development of a complicated deformational cycle showing the superficial evidence of a sinistral lateral shear zone. At the beginning the area was affected by a NE-SW compression including reverse, dextral and sinistral strike-slip faulting. This was followed by Early Pleistocene sinistral transtension characterized by a NW-SE direction of least principal stress and sinistral normal-slip faulting. During Late Pleistocene-Holocene times the transtension was concentrated along E-W faults. Tectonic control in the distribution of volcanism has also been recognized. The Basin and Range phase controlled the deposition of the Miocene volcanic and clastic units, particularly the effusion of basaltic lavas connected with the latest extensional movements of the same phase. The Mexican Volcanic Belt sequence is strictly linked with the development of a large E-W sinistral lateral shear zone, active from the Pliocene to the Present, which shows the extensional component progressively prevailing over the shear one