Large scale structures in the Nevado-Filabride Complex and crustal seismic fabrics of the deep seismic reflection profile ESCI-Béticas2

Abstract

The ESCI-Béticas 2 deep seismic reflection profile cuts across the Albarán Domain, an allocthonous composite terrane that has undergone complex orogenic evolution. After the development of several crustal thickening episodes, it was severely thinned during the Early and Middle Miocene and later folded. Two large-scale anticlines coinciding with the Sierra Nevada and Sierra de los Filabres mountain ranges have been identified. The anticlines are open and North-vergent and developed in the Late Tortonian. An analysis of the geometry of these folds and comparison with the seismic image of the upper crust in the ESCI-Béticas2 profile has led us to conclude that these structures are related to flat and ramp contractional faults. The reflection Moho found between 10.5 and 11 s TWT is continuous and nearly flat. A prominent Mid-Crustal Reflector (MCR), located variously from 5.5 to 6.5 s TWT, separates two crustal levels with different reflectivity patterns. The crust above the MCR is nearly transparent, although locally there are bands of high reflectivity. The most notable of these bands is the UCR (Upper Crustal Reflector), interpreted as a mylonitic band. The deep crust, in contrast, is highly reflective and shows broad domains of laminated crust, possibly due to pervasive ductile shearing. The deep crustal reflectors are cut by less reflective, SSW-dipping bands, with a geometry that can be interpreted as extensional shear zones.