Structural evolution of the early Miocene in the eastern Betic internal-external zone boundary (SE Spain)

Abstract

Abstract The Internal-External Zone boundary (IEZB) in the eastern Betic Cordillera partially coincides with the Cadiz-Alicante Accident, mainly a major transcurrent fault of N060E direction. The study of an area located along the IEZB at a point where it separates from the Cadiz-Alicante accident has provided details concerning the geodynamic evolution of the cordillera at the moment of its structuration. Here the Internal Zone, consists of rocks assigned to the Malaguide Complex, dating its last sedimentation to the Aquitanian, and deposits assigned to the Vinuela Group (early-middle Burdigalian). The nappes of the Internal Zone were emplaced during the latest Aquitanian and the Vinuela Group (here the El Nino Formation) sealed it but was afterwards affected by the collision with the External Zone. On the other side of the boundary, the External Zone comprises two tectonic units: the Penarrubia Unit (late Cretaceous-middle Burdigalian), which is made up mainly of limestones and marls, and the El Frances Chaotic Complex composed by a set of different lithologies, all from the External Zone in a marly matrix that could be interpreted as a collisional melange formed in the early-middle Burdigalian. The contact between the two domains corresponds to a backthrust of the External Zone over the Internal Zone which occurred in the middle Burdigalian. The deposits sealing the IEZB are dated by calcareous nannofossils and planktonic foraminifera as late Burdigalian, and comprise clasts from both domains.