Late extensional shear zones and associated recumbent folds in the Alpujarride subduction complex, Betic Cordillera, southern Spain


  • M. OROZCO Departamento de Geodinámica, I.A.C.T., Universidad de Granada-CSIC 18071 Granada, Spain.
  • F. M. ALONSO-CHAVES Departamento de Ciencias de la Tierra, Facultad de Ciencias Experimentales, Universidad de Huelva 21071 Huelva, Spain.
  • J. P. PLATT Department of Earth Sciences, University of Southern California, Los Angeles CA 90089-0740, USA.


Extensional shear zone, Recumbent folds, Alpujarride Complex, Betic Cordillera


The existence in the Alpujarride Complex (Betic Cordillera, southern Spain) of a relatively continuous extensional event (following crustal thickening) is based on detailed structural studies and is consistent with the P-T paths and geochronological data established for the Alpujarride rocks. According to our research, the Alpujarride Complex contains two large-scale shear zones accommodating early Miocene extension. The shear zones contain km-scale recumbent folds, some with sheath fold geometry, and megaboudinage structures, and are closely associated with detachment faults.

Large-scale folds and boudins cause dome-like undulations in the detachments, which are inferred to overlap in time with the deformation in the shear zones. One shear zone in the eastern part of the orogen is top-N; the other, in the western part, is top-E. The change in the shear direction may represent a temporal evolution in the direction of shear, possibly related to a change in the subduction direction in space and time.