Geometría y Cinemática de Fallas recientes en el margen septentrional del mar de Alborán (sector de Maro, provincia de Málaga)

Resumen

The more recent structures in the northern continental margin of the Alboran Sea are NW-SE high-angle normal faults, oblique to the present coastal line and also to the actual crustal thinning pattern. The geometry and kinematics, with particular emphasis on the fault linkage patterns, of two of these recent faults with a preserved fault-scarp, the Las Alberquillas (av. 136/69° SW) and the Maro (av. 149/58° NE) faults, have been studied. The Maro fault is formed by several, small, and non-cylindrical fault segments (< 500 m length) frequently displaced by transfer faults, whereas the Las Alberquillas fault is formed by two long and planar fault segments (total length~ 3800 m), linked by a narrow en-echelon step, thus suggesting a major displacement in this master fault (estimated total displacement of the fault= 38 m). The maximum displacement in the Las Alberquillas fault occurs near its SE tip line, therefore suggesting the overlapping interference with a close and related synthetic normal fault in relay towards the SE in the Alboran Sea. Kinematic data on fault surfaces indicate a normal oblique sense of movement of these faults (rake of the main striae > 60°), being dextral and sinistral in the Las Alberquillas and the Maro faults, respectively. Other, secondary striae, with a right- or left-lateral sense of displacement occurs also locally near major corrugations in these faults. Average fault plane solution in both faults results in a NNE-SSW subvertical compression (P ax/s= 66/033° and 77/232°) and subhorizontal extension (T axis= 23/231° and 13/060°). Last fault slip occurred probably during the lower Pleistocene (-800 ka), on the basis of the geometrical relationships with alluvial-fan deposits and radiometric data