Superposition of extensional detachments during the Neogene in the internal zones of the Betic cordilleras

F. González-Lodeiro (Y) 7 F. Aldaya 7 J. Galindo-Zaldívar A. Jabaloy Departamento de Geodinámica, Universidad de Granada, E-18071 Granada, Spain E-mail: jgalindo6goliat.ugr.es Abstract In the internal zones of the Betic cordilleras, extensional structures have developed from the Upper Oligocene to the present day; they are contemporaneous with compressional structures (folds and thrusts) in the external zones. From the Upper Oligocene to the Aquitanian, extension occurred in the Maláguide/Alpujárride detachment, and related structures show varying kinematics in different sectors. Younger deformations with a top-to-the-N sense of movement have affected Nevado-Filábride (ductile shear zones), Alpujárride (ductile and brittle shear zones) and Maláguide rocks (normal faults). At least from the Late Burdigalian up to the Lower Tortonian, displacements have occurred in the Alpujárride/Nevado-Filábride detachment. Deformations have been generally non-coaxial, with a topto-the-W sense of movement. Stretching lineation trends in the Nevado-Filábride rocks curve from E to W suggesting a progressive variation of the ductileshear-zone kinematics related to the Alpujárride/Nevado-Filábride detachment between the Aquitanian and Lower Tortonian stages. Deformations from the Lower Tortonian to the present day are normal faults, formed in extensional settings in the upper part of the crust, and folds and strike-slip faults which indicate N– S to NNW–SSE shortening directions and E–W to ENE–WSW extension directions.