The impact of internal waves on upper continental slopes: insights from the Mozambican margin (SW Indian Ocean)

Type Article
Date 2020-05
Language English
Author(s) Miramontes Elda1, 2, Jouet Gwenael2, Thereau Estelle2, Bruno Miguel3, Penven Pierrick4, Guerin Charline2, Le Roy Pascal1, Droz Laurence7, Jorry StephanORCID2, Hernández‐molina F. Javier5, Thiéblemont Antoine5, 6, Silva Jacinto Ricardo2, Cattaneo AntonioORCID2
Affiliation(s) 1 : UMR6538, CNRS‐UBO, IUEM, Laboratoire Géosciences Océan Plouzané 29280 ,France
2 : IFREMER, Unité Géosciences Marines Plouzané 29280 ,France
3 : CACYTMAR. Univ. Cádiz, Avda República Saharaui S/N Puerto Real 11510 Cádiz ,Spain
4 : UMR 6523 CNRS, IFREMER, IRD, UBO, Laboratoire d'Océanographie Physique et Spatiale Plouzané 29280, France
5 : Department of Earth Sciences, Royal Holloway University of London Egham Surrey TW20 0EX ,United Kingdom
6 : TOTAL, R&D Frontier Exploration program Avenue Larribau 64000 Pau ,France
7 : UMR6538, CNRS‐UBO, IUEM, Laboratoire Géosciences Océan Plouzané 29280 ,France
Source Earth Surface Processes And Landforms (0197-9337) (Wiley), 2020-05 , Vol. 45 , N. 6 , P. 1469-1482
DOI 10.1002/esp.4818
Keyword(s) contourite, sediment drift, bedform, sedimentary processes, tide, internal solitary waves, bottom currents
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. On the other hand, 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.

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Miramontes Elda, Jouet Gwenael, Thereau Estelle, Bruno Miguel, Penven Pierrick, Guerin Charline, Le Roy Pascal, Droz Laurence, Jorry Stephan, Hernández‐molina F. Javier, Thiéblemont Antoine, Silva Jacinto Ricardo, Cattaneo Antonio (2020). The impact of internal waves on upper continental slopes: insights from the Mozambican margin (SW Indian Ocean). Earth Surface Processes And Landforms, 45(6), 1469-1482. Publisher's official version : https://doi.org/10.1002/esp.4818 , Open Access version : https://archimer.ifremer.fr/doc/00605/71730/