Development of Tectonically-Confined Submarine Fans from the Tabernas-Sorbas Basin, SE Spain

Hodgson, David M.¹, Kevin T. Pickering² (1) University of Liverpool, Liverpool, United Kingdom (2) UCL (University Colege London) Earth Sciences Dept, London, United Kingdom

A study of late Tortonian deep-water systems in the Tabernas-Sorbas Basin, SE Spain, has revealed several intrabasinal fold structures that deformed the seabed during sedimentation. The growth of seabed folds was the primary control on the down-slope development of a multiple-sourced channelised submarine slope system. Large volumes of coarse clastic sediment were transported down-slope into a tectonically-confined area referred to as the Sandy System. The presence of seabed topography is highlighted by significant changes in stratigraphic thickness across fold structures. This seabed topography controlled the routeing and storage of sediment and, therefore, the facies distribution, the architecture, and the partitioning of depocentres of different provenance and calibre.

Deposits on the downstream flanks of anticlines are coarse-grained (cobble-grade), with common deep scours surfaces, regular concentrations of (fine-grained) rip-up clasts, and widespread development of steep cross-bedded sediments. Onlap of sandstones onto intrabasinal slopes are also common. In the centre of synclines at the same stratigraphic interval, the sediments are fine-grained, paleocurrents are less focussed, and evidence of rapid deposition (dewatering) is common. The repetition of similar facies associations at similar geographic positions across different structures is interpreted to indicate the occurrence of headward incision through filled up-dip depocentres as sediment-laden flows encountered steeper topography on downstream flanks. This study shows the importance of understanding the impact of seabed topography on sediment-laden density currents in order to aid subsurface exploration.