SYNTECTONIC SEDIMENTATION IN A NEOGENE STRIKE-SLIP BASIN CONTAINING A STACKED GILBERT-TYPE DELTA (SE SPAIN)

The Pliocene sedimentation in the Cerro Blanco/El Barranquete subbasin (CBB subbasin) that forms part of the larger Almeria-Nijar-Carboneras basin (ANC basin) is controlled by a releasing overstep and a restraining zone in the NE-trending Serrata strike-slip fault zone. The sedimentary development of this subbasin can be considered in three stages of a fault-kinematic model. During Stage I a wave-influenced shoaling zone was present in front of an emergent Serrata cape to the NE, with a basin to the SW and W. Uplift of the shoaling zone in a restraining N080E-trending Cerro Blanco fault zone (CB fault zone) is evidenced by the following syn-tectonic sedimentary phenomena: (a) a rotational unconformity towards the NW; (b) four deepening pulses in the shallow-water zone; (c) massflow deposits originating from a near-coastal zone possibly triggered by tectonic pulses. During Stage II the uplifted zone became increasingly shallow and finally emerged. Quartz pebbles in the sediments that indicate a land connection between the Serrata cape and the metamorphic basement in the north, differentiate this stage from the previous one. Prograding shoreline deposits marked the outbuilding of the Serrata cape towards the SW. An episodically subsiding zone due to a releasing overstep between the sinistral N040E-trending NW Serrata boundary fault (NWSB fault) and B fault during Stage IIa is indicated by a southwestward outbuilding fandelta. During this stage there was only one depocentre. During Stage IIb the depocentre of the subsiding zone split up. This shifting of depocentres is explained according to the releasing overstep model by an increase of the overlap between the NWSB fault and the B fault. During Stage III the CBB subbasin became continental and was inverted as demonstrated by its present-day relief. The area was severely faulted by N040E-trending R and Y shears on a metre-scale, which led to an estimated cumulative sinistral displacement of 2 km since fandelta deposition. The present-day activity of the NWSB fault is shown by sinistrally deflected stream courses and pressure ridges.