Crustal structure of the central sector of the Betic Cordillera (SE Spain)

Abstract

Deep seismic reflection, gravimetric, and magnetometric data allow the main features of the deep structure of the central sector of the Betic Cordillera to be established. The Moho is horizontal or dips slightly toward the S below the mountain chain, and its morphology has no direct relationship with the region's topography. The deep reflectors are not deformed by the Neogene kilometric‐scale folds that produced the main topographic features, probably due to the existence of detachment levels in the crust. The crust is slightly thickened in the Betic Cordillera (almost 35 km) and has an abrupt transition to the thin crust of the Alborán Sea (15 km in the central Alborán Sea) along an E‐W oriented narrow band, subparallel to the coast line, where the Moho dips more than 60°N. The Neogene evolution of the mountain chain caused compressive deformation in the External Zones. In the Internal Zones, pre‐Tortonian low‐angle normal faults developed after the alpine metamorphism, and later high‐ and low‐angle normal faults and strike slip faults occurred up to the Quaternary. Geophysical and field geology data can be used to establish a geological model for the recent evolution of the crustal deformation. In this model, the recent evolution of the region is probably determined by thrusting of the thin continental crust of the Alborán Sea toward the NW over the southern margin of the Iberian Massif. This deformation could be a consequence of the oblique convergent movement between the African and Eurasian plates, which may have uplifted the entire region, causing regressions in the sedimentary basins and the formation of folds and extensional structures in the upper part of the thickened crust.