Structural evidence of post-Messinian reverse faulting in the northern limb of the Sierra Alhamilla antiform (southeastern Betics, SE Spain)

Resumen

The North Alhamilla reverse fault is the western strand of the dextral transpressive Polopos fault zone, a fault system conjugate to the sinistral Palomares fault zone in the southeastern Betics. We present new structural and mapping data that suggest its recent activity after the late Pleistocene (> 70 ky). This fault bounds the entire northern limb of the Sierra Alhamilla antiform and has a reverse NNW-wards displacement forming the contact between the metamorphic basement and the Neogene sedimentary cover of the Sorbas-Tabernas basin. The main fault cuts through early Tortonian turbidites and the Quaternary alluvial fans at the Sierra Alhamilla mountain front (400-70 ky) forming a fault-propagation fold structure. During the Pleistocene until present the reverse displacement along the North Alhamilla reverse fault migrated westwards, where faults have propagated forward into the sedimentary basin cutting the Pleistocene alluvial fan surfaces. The North Alhamilla reverse fault is locally segmented by NW-SE oriented dextral transfer fault segments like the Turrillas fault.