Neogene evolution of the Sorbas basin (SE Spain) determined by paleostress analysis

Abstract

The Neogene subsidence history of the Sorbas basin, situated in the Internal Zone of the Betic Cordilleras of southeastern Spain, is strongly controlled by strike-slip deformation. The sedimentary sequence of the basin offers a good control on the timing of separate phases of fault activation. The southern border of the Sorbas basin is formed by a major east-west trending fault zone (the Gafarillos fault zone) which consists of intermixed slivers of pre-Neogene basement blocks and Neogene basin sediments. Fault patterns and paleostress analysis both indicate that major displacement along this fault zone was dextral with a N310E-oriented maximum principal stress axis. Strike-slip movement along the east-west-oriented faults ended during the earliest Messinian after a minimum of 6 Ma of activation. Paleostress analysis indicates a subsequent phase of strike-slip fault movement present in sites of up to Early Pliocene age. The maximum principal stress axis orientation is N350E for this phase. This deformation is synchronous with sinistral displacement along the Palomares fault zone situated directly to the east of the study area. Subsequently, our paleostress analysis indicates an extensional regime during the Late Pliocene to Quaternary. However, extensional tensors were calculated at a number of sites possibly representing local stress regimes coexisting with the main strike-slip deformation and Sorbas basin subsidence. Folding of Tortonian sediments points out that local compressional deformation took place as well during the Neogene basin history. Observed wide ranges for the ellipsoid shapes of the calculated tensors support the existence of lateral stress variations.