Geometry and Late-Miocene to the Recent evolution of the western Betics external orogenic wedge

Abstract

The external zones of orogens are frequently deformed into fold-and thrust belts. Fold-and-thrust belts depict wedges in crosssection defined by the α angle, which is the slope of the syn-orogenic topography, and β angle, which is the basal detachment’s dip. The aim of this work is to study the geometry and evolution of the western Betics wedge and to compare with the Central Betics. To do that, geological cross-sections, interpretation of seismic profiles and well data were used. The overall α angle is 1.34º, however, a sharp topographic drop coincides with a change in the structural style within the fold-and thrust belt. Both fold-and-thrust belt segments analysed separately yield α angles lower than 0.6º. The angle β at the external wedge is ca. 3º. There are no evidences of steps in the basement top topography. Consequently, the western Betics wedge probably propagated since the Early Miocene to Recent without significant stagnation during its front propagation, unlike the central Betics wedge. Recent propagation of the deformation accreted the internal parts of the foreland basin (Serravallian to Quaternary sediments) to the Betics fold-and-thrust belt.