Contourite sands in the Gulf of Cadiz : characterisation, controls and wider implications for hydrocarbon exploration

Abstract

This study uses an extensive data‐set from a sand‐rich contourite depositional system located in the Gulf of Cadiz. Newly acquired data, targeting a modern contourite sandy depositional system in the eastern Gulf of Cadiz, has been integrated with historical data, including a seismic survey over a Pliocene mixed system in the northern Gulf of Cadiz. Seismic, core and sediment analysis has been used to assess the controls on the system, and characterise the sediments. The presented study gives a new complete view of past circulation of the Mediterranean Outflow Water and contourite deposition in the eastern Gulf of Cadiz over the upper, mid and lower slope. It also identifies a mixed system in the Pliocene section of the northern Gulf of Cadiz. This allows us to make the following contributions to the field; 1. A new model from Quaternary evolution of the eastern sandy contourites, and Pliocene evolution of a sandy mixed system the northern Gulf of Cadiz. 2. A detailed examination of the sand facies and sediment of the Gulf of Cadiz and a new set of contourite sand facies models proposed. 3. A thorough examination of the controls on contourite formation, and their integration in a sequence stratigraphic framework. 4. A review of the hazards bottom currents pose to deep water exploration, and the reservoir potential of contourite sands and other facies. The Gulf of Cadiz provides a good modern day analogue for contourite sands. They show various facies and sedimentological characteristics that are tied to depositional processes. They are also highly cyclic in nature, on a variety of time scales. If they can be positively identified in the subsurface, they have the capacity to make potential hydrocarbon reservoirs. The facies and sedimentological models presented here, and their integration into a sequence stratigraphic model will aid the positive identification of these deposits in the future.