Echofacies interpretation of Pleistocene to Holocene contourites on the Demerara plateau and abyssal plain

• Published in: Interpretation
• Main Authors: Tallobre, Cédric, Loncke, Lies, Droz, Laurence, Marsset, Tania, Uusõue, Mirjam, Roest, Walter, Fanget, Anne-Sophie, Bassetti, Maria-Angela, Giresse, Pierre, Bayon, Germain
• Other Authors: Laboratoire Géodynamique et enregistrement Sédimentaire (LGS), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire Aléas géologiques et Dynamique sédimentaire (LAD)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU]Sciences of the Universe [physics]; NADW
• Online Access: https://hal.science/hal-04203342; https://doi.org/10.1190/INT-2020-0159.1

Off French Guiana and Surinam, NADW and AABW oceanic currents contour the Demerara marginal plateau, which promotes the formation of contourites. We have studied these contourites thanks to a new compilation of high-resolution sub-bottom profiles calibrated by sedimentary cores. The echo-facies and isopach maps we constructed highlight a sedimentary distribution parallel to the isobaths. The presence of moats along the slope is confirmed by the observation of parallel, elongated, sedimentary depleted zones and echo-facies strongly affected by diffraction hyperbola and transparent echo-facies. We interpret these features to be related to eroded slopes and Mass Transport Deposits. In contrast, the sedimentary drifts we mapped are characterized by elongated and thick slope-parallel depocentres displaying bedded echo-facies with wave-like bedforms. According to our interpretation, they result from interactions between currents and the seafloor. Seismic wipe-outs frequently affect those drifts, possibly resulting from high water or organic contents.