Structure and kinematics of the Ayora-Cofrentes Diapir (eastern Betics). Role of basement faulting in the salt and suprasalt deformation of the Mesozoic cover

Abstract

The Ayora-Cofrentes Diapir is a 34 km long N-trending salt wall cutting the Valencian Domain that is made by Middle to Upper Triassic salt. On both sides, it is flanked by parallel half grabens offsetting the subtabular strata of the Jurassic to Cretaceous suprasalt carbonate successions. Based on detailed geological mapping and cross-sections, one of them supported by a new magnetotelluric profile, this study analyses the structure and kinematics of this salt wall with the purpose of establishing the role played by the subsalt structure in its development; and, thus, help in the interpretation of diapirs currently incorporated in fold and thrust belts. In this regard, the study evidences the presence of a subsalt basement fault (the Ayora Fault), active as extensional during the Early Jurassic, and reactivated with a reverse throw sometime between the latest Cretaceous and middle Miocene. Both motions are older than the salt wall growth (middle-late Miocene). This strongly suggest that the Ayora-Cofrentes Diapir was not triggered by the vertical motion of the underlying Ayora basement fault but by thin-skinned processes for which this pre-existing basement fault appears to have played a crucial role as salt/suprasal strain localizer.