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

摘要

The existence in the Alpujarride Complex (Betic Cordillera, southern Spain) of a relatively continuous extensionalevent (following crustal thickening) is based on detailed structural studies and is consistent with the P-T paths andgeochronological data established for the Alpujarride rocks. According to our research, the Alpujarride Complexcontains two large-scale shear zones accommodating early Miocene extension. The shear zones contain km-scalerecumbent folds, some with sheath fold geometry, and megaboudinage structures, and are closely associated withdetachment faults.Large-scale folds and boudins cause dome-like undulations in the detachments, which are inferred to overlap intime 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 directionof shear, possibly related to a change in the subduction direction in space and time.