Description of a contourite depositional system on the Demerara Plateau: Results from geophysical data and sediment cores
2016
The Demerara Plateau, belonging to the passive transform margin of French Guiana, was investigated during the IGUANES cruise in 2013. The objectives of the cruise were to explore the poorly-known surficial sedimentary column overlying thick mass transport deposits as well as to understand the factors controlling recent sedimentation. The presence of numerous
bedformsat the seafloor was observed thanks to newly acquired IGUANES bathymetric, high resolution seismic and chirp data, while sediment cores allowed the characterization of the deposits covering the mass transport deposits. Modern oceanographic conditions were determined in situ, using mooring monitoring over a 10-month period. Our data indicate the presence of a
ContouriteDepositional System along the Demerara Plateau, most likely related to bottom current activity of the
North Atlantic Deep Water(NADW). However, at the regional scale, large
longitudinal wavesparallel the NADW flow. Their shape and orientation seem to be inherited from interactions between bottom currents and paleomorphologies expressed at the top of mass transport deposits. Their evolution is possibly driven by the intensity of bottom current activity that might have changed over time. Overall, this work presents an integrated approach combining seismic and
sedimentologicalevidence to study the processes at the origin of
contouriteformation in the Demerara Plateau. Other regional factors, such as local slope values and slope instability, also control sedimentation.
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