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

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...

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Bibliographic Details
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
Format: Article in Journal/Newspaper
Language:English
Published: Society of Exploration Geophysicists 2021
Subjects:
NADW
Online Access:https://archimer.ifremer.fr/doc/00680/79223/86918.pdf
https://doi.org/10.1190/INT-2020-0159.1
https://archimer.ifremer.fr/doc/00680/79223/
Description
Summary: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.

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