Impact of syndepositional faulting on gravity current behaviour and deep-water stratigraphy: Tabernas-Sorbas Basin, SE Spain

Seabed faulting can have a significant impact on the routeing and behaviour of gravity currents depositing sand on deepwater basin floors. The Neogene El Cautivo Fault in the Tabernas-Sorbas Basin, SE Spain, is a rare example of a fault that demonstrably propagated through to the seabed during turbidite deposition, allowing the interplay between deepwater sedimentation and tectonics to be explored. The fault is associated with a wide (up to 350 m) gouge zone that varies significantly in thickness along its length, reflecting upward expansion towards the original seabed and progressive burial as fault activity ceased. Kinematic and stratigraphic evidence indicate that the fault was a dextral oblique strike-slip fault that accommodated an area of deeper ponded bathymetry (a ‘mini-basin’) and accelerated subsidence on its southern flank. Active faulting controlled the routeing of turbidity currents (revealed by changing provenance across the structure), rates of seabed deformation (resulting in differential subsidence and ‘growth’ of the stratigraphy), and the behaviour of the ponded currents (producing distinctive bipartite beds when deposition was in localized ponded depressions). The seabed expression of the fault varied from a forced fold, which warped the surface causing local wedging and onlap in the vicinity of the structure, and an unstable scarp that locally collapsed. The fault gouge fabrics and vein arrays are consistent with faulting of soft, water-rich sediment close to the seabed.