The Le Danois Contourite Depositional System: Interactions between the Mediterranean Outflow Water and the upper Cantabrian slope (North Iberian margin)

The Le Danois Contourite Depositional System (CDS), located in an intraslope basin along the Cantabrian margin, is unique with respect to the known sedimentary systems along the upper slope of the Biscay margin. Whereas the steep Biscay slopes are dominated by downslope processes, the Le Danois CDS has been generated by alongslope processes and has a strong potential to contain a record of the Neogene palaeoceanography. This paper will focus on the onset, development and present-day functioning of this system with respect to its unique morphological control and the responsible local oceanographic processes. New bathymetric and seismic reflection data show that the past and present Le Danois CDS is shaped by the Mediterranean Outflow Water, conditioned by seafloor irregularities and two topographic highs; the large Le Danois Bank and the smaller Vizco High. The seismic stratigraphic analysis carried out on the contourite deposits has allowed to identify 3 seismic sequences, separated by 3 major regional discontinuities. Changes in depositional styles, the vertical stacking of seismic units and the nature of the discontinuities suggest a correlation with the development of the Cadiz CDS and well-known palaeoceanographic events along the NE Atlantic margin. The first clues for bottom-current deposits are identified in the Lower Sequence, which is developed after tentatively the Lower Pliocene. The drift deposits of both the Lower and Middle Sequences were confined into two palaeobasins within the intraslope basin. However, from the Middle Pleistocene Revolution (0.9 Ma) onwards, the contouritic deposition is intensified due to the switch to a “full glacial” mode with 100 ka cyclicity. This has allowed the development of the present-day depositional and erosive features, such as respectively elongated mounded and separated drifts, plastered drifts, moats and slide scars.