Neogene-quaternary evolution from transpressional to transtensional tectonics in Northern Central America controlled by cocos: Caribbean subduction coupling change

Abstract

The structural evolution of the western boundary of the Chortis Block, particularly in the Central America Volcanic Arc crossing El Salvador is poorly known. We have done a kinematic analysis from seismic and fault slip data and combined our results with a review of previous regional studies. This approach allowed us to constrain the tectonic evolution and the processes that control the deformation in northern Central America. Along the active volcanic arc we identified active transtensional deformation. On the other hand, we have identified two deformation phases in the back arc region: A first one of transpressional wrenching close to simple shearing (Miocene); and a second one characterized by almost E–W extension coincident with the extensional direction of the Honduras grabens opening. Our results reveal a change from transpressional to transtensional shearing coeval with a migration of the volcanism towards the trench in Late Miocene times. The strain change could be related to a transition from coupled to decoupled interface on the Cocos—Caribbean subduction, which could be caused by a slab roll-back of the Cocos Plate beneath the Chortis Block. The combination of different degrees of coupling on the subduction interface, together with a constant relative eastward drift of the Caribbean Plate, control the deformation style along the western boundary of the Chortis Block.