The impact of internal waves on upper continental slopes: insights from the Mozambican margin (southwest Indian Ocean) |
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Authors: | Elda Miramontes Gwenael Jouet Estelle Thereau Miguel Bruno Pierrick Penven Charline Guerin Pascal Le Roy Laurence Droz Stephan J. Jorry F. Javier Hernández-Molina Antoine Thiéblemont Ricardo Silva Jacinto Antonio Cattaneo |
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Affiliation: | 1. UMR6538, CNRS-UBO, IUEM, Laboratoire Géosciences Océan, Plouzané, France;2. IFREMER, Unité Géosciences Marines, Plouzané, France;3. CACYTMAR, Universidad de Cádiz, Puerto Real, Cádiz, Spain;4. UMR 6523 CNRS, IFREMER, IRD, UBO, Laboratoire d'Océanographie Physique et Spatiale, Plouzané, France;5. Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, UK;6. Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, UK TOTAL, R&D Frontier Exploration Programme, Pau, France |
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Abstract: | Evidences of sedimentation affected by oceanic circulation, such as nepheloid layers and contourites are often observed along continental slopes. However, the oceanographic processes controlling sedimentation along continental margins remain poorly understood. Multibeam bathymetry and high-resolution seismic reflection data revealed a contourite depositional system in the Mozambican upper continental slope composed of a contourite terrace (a surface with a gentle seaward slope dominated by erosion) and a plastered drift (a convex-shape sedimentary deposit). A continuous alongslope channel and a field of sand dunes (mainly migrating upslope), formed during Holocene, were identified in the contourite terrace at the present seafloor. Seismic reflection data of the water column show internal waves and boluses propagating in the pycnocline near the upper slope. The channel and the dunes are probably the result of the interaction of the observed internal waves with the seafloor under two different conditions. The alongslope channel is located in a zone where intense barotropic tidal currents may arrest internal solitary waves, generating a hydraulic jump and focused erosion. However, upslope migrating dunes may be formed by bottom currents induced by internal solitary waves of elevation propagating landwards in the pycnocline. These small-scale sedimentary features generated by internal waves are superimposed on large-scale contouritic deposits, such as plastered drifts and contourite terraces, which are related to geostrophic currents. These findings provide new insights into the oceanographic processes that control sedimentation along continental margins that will help interpretation of palaeoceanographic conditions from the sedimentary record. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd |
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Keywords: | contourite sediment drift bedform sedimentary processes tide internal solitary waves bottom currents |
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