Kinematic evolution of the continental active triple junction of the western Mexican Volcanic Belt.

Microtectonic measurements were carried out in the area of the triple junction of the western Mexican Volcanic Belt. Fault motions were of left-lateral type during the Late Miocene-Early Pliocene and of right-lateral type during the Late Pliocene-Quaternary along the NW-SE arm. Late Miocene-Early-Pliocene left-lateral faulting and Late Pliocene-Quaternary left-lateral transtension characterize the E-W arm. The third arm is a Plio-Quaternary NNE graben. The data presented in this work allow us to propose a block fragmentation of the southern margin of the North American Plate. The block evolution is coherent with the tectonic history of the Gulf of California and of the Middle American Trench. -from Authors