The role of tectonics and diapirism in deep-water depositional systems’ evolution: a case study of contourite features in Gulf of Cadiz

The influence of tectonic activity on deep-water sedimentation has long been recognized. The Gulf of Cadiz located in the proximity to the Azores-Gibraltar Fracture Zone and western front of the Betic–Rif provides a remarkable setting for the investigation of the evolution of deep-water depositional systems in an active tectonic setting. Furthermore, extensive diapiric activity. These include an extensive contourite depositional system, down-slope turbidite and mass transport deposits, and pelagic/hemipelagic. The contourite depositional system has been established along the continental slope of the SW Iberia. In the southern Gulf of Cadiz (NW Morocco), contourites features are less developed. These depositional systems were investigated using a regional 2D and 3D seismic reflection and parasound dataset, complemented by multibeam bathymetry, well information and an earthquake compilation.
Tectonic activity influenced depositional processes and sedimentary architecture of deposits. Changes from contourite to turbidite or mass transport deposits indicate periods of increased sedimentary instability due to tectonic activity, while homogeneous and continuous sedimentation suggests the decrease of tectonic activity. It was also recognised that the size and geometries of contourite deposits depend on the accommodation space (i.e., subsidence or uplift), local changes in depocenter volume due to diapiric control and on the presence of morpho-structural highs or lows and diapirs.
The long-term evolution of the SW Iberia and NW Morocco contourite deposits reveal the influence of tectonic and diapiric events interacting with oceanographic processes as i) the availability of depositional space, ii) the bottom-current circulation and iii) the sediment supply.
The evolution of the depositional systems developed in the Gulf of Cadiz was marked by the complex interplay of tectonic, oceanographic and climatic factors since the late Miocene. This work demonstrates that contourite deposits constitute a valuable high-resolution archive for the recognition of regional and local tectonic events at regional and local scales.