Evolución geológica desde el Mioceno del sector noroccidental de la Depresión de Granada (Cordilleras Béticas)

Resumo

The Granada Depression is one of the largest depressions located in the central Betic Cordilleras. In the studied area, the Neogene and Quaternary rocks lie unconformably over the carbonated units of the Subbetic. Three tectonic units separated by low angle faults compose the subbetic basement. The middle and lower tectonic units are separated by a fault that shows two stages of translation with top-to-the SW and N sense of motions. The contact between the middle and upper units only shows the latest stage of translation. The structures that individualise the Granada Depression have a post-Tortonian age. The two most relevant faults are normal and have an approximate E-W strike and middle to low southward dips. Seismic reflection profiles reveal two main stages of normal activity in the southern fault with an intermediate compressional event. The wedge shape of the sedimentary fill of the Granada Depression, thickening towards the N, may have been produced by the activity of this fault system. However, Plio-Quaternary rocks are affected by new compressional and extensional deformations that have been revealed by the study of striated pebbles, vertical joints and normal faults. The alternance of compressional and extensional focal mechanisms in the area also indicates that the present-day stress field has the same features. The tectonic evolution model should take into account the alternance of these extensional and compressional deformations that have not been taken into account in the previous models proposed for the area.