Miocene deformation front propagation and strain partitioning within the fold-and-thrust belt of the Central Betics

The External Zones of migrating orogenic arcs can be deformed as fold-and-thrust belts where the advance of the deformation front toward the foreland is contemporary to the arc-lengthening. The Sierra de Cabra, in the Central Betics, is made up of Subbetic units surrounded by synorogenic, Middle to Upper Miocene rocks. The combined data from surface and seismic profiles show the presence of partially coetaneous structures during the Middle Miocene: (i) a NNW-verging thrust system detached within Triassic evaporites accommodating arc-perpendicular shortening, (ii) N-S, NW-SE and NNE-SSW normal faults accommodating WSW-ENE stretching and (iii) WSW-ENE normal faults. These results allow us to interpret the Sierra de Cabra as the Langhian Betic fold-and-thrust belt front. Additionally, the WSW-ENE stretching contributes to the structural and topographic segmentation along-strike the Betics. The Miocene strain partitioning here proposed is similar to that found in the Western Betics.