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1. Direct sediment transfer from land to deep-sea: Insights into shallow multibeam bathymetry at La Réunion Island

Author

Nicolas Villeneuve, Anne Deschamps, E. Sisavath, Romain Cancouët, Christophe Delacourt, Nathalie Babonneau, Stephan J. Jorry, Jérôme Ammann, Patrick Bachèlery, Aude Mazuel, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), Laboratoire Environnements Sédimentaires (LES), 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 Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), LabexMer (ANR-10-LABX-19-01), Université de La Réunion (UR)-Institut de Physique du Globe de Paris, Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
canyon head, Turbidity current, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Fluvial, Submarine canyon, Surf zone, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, River mouth, Bathymetry, 14. Life underwater, turbidity current, Sea level, 0105 earth and related environmental sciences, Canyon, geography, geography.geographical_feature_category, Geology, coastal instability, submarine canyon, 13. Climate action, hyperpycnal flow
Abstract

International audience; Submarine canyon heads are key areas for understanding the triggering factors of gravity currents responsible for the transfer of detrital sediment to the deep basins. This contribution offers a detailed picture of canyon heads off La Réunion Island, with high-resolution multibeam bathymetry in the water depth range of 4-220 m. The present feeding of the Cilaos turbidite system, one of the largest modern volcaniclastic systems in the world, is deduced from morphological and sedimentological interpretations of newly acquired data. The study highlights small-scale sedimentary features indicating hydrodynamic and sedimentary processes. A direct connexion between the Saint-Etienne river mouth and submarine canyons is evidenced by the complete incision of the shelf and the presence of canyon heads connected to the modern deltaic bar. This direct connection, supplied by river torrential floods (cyclonic floods every two or three years), suggests the continuity of high-density fluvial flows to submarine gravity flows, forming hyperpycnal flows in the canyon. The initiation of secondary submarine gravity flows by storm waves (large austral waves and cyclonic waves) is also proposed for submarine canyons with large canyon heads developed in the surf zone from a sandy coastal bar. Bedforms in active canyon axis are considered as an indicator of the frequent activity of high-density turbidity currents. Moreover, a morphological record of last glacial and deglacial sea level variations is preserved, and particularly the Last Glacial Maximum sea level with the presence of small vertical cliffs, observed in this bathymetric data, which likely corresponds to a paleo-shoreline or paleo-reefs.

Published
2013

2. Turbidity current activity along the flanks of a volcanic edifice: The Mafate volcaniclastic complex, La Réunion Island, Indian Ocean

Author

Patrick Bachèlery, Stephan J. Jorry, Nathalie Babonneau, Christophe Delacourt, E. Sisavath, Aude Mazuel, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris, Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), Laboratoire Environnements Sédimentaires (LES), Géosciences Marines (GM), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)

Subjects
Turbidity current, La Réunion Island, 010504 meteorology & atmospheric sciences, Stratigraphy, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, Pyroclastic rock, 010502 geochemistry & geophysics, Turbidite, 01 natural sciences, Deep sea, Sedimentary depositional environment, La Reunion Island, Bathymetry, 14. Life underwater, Geomorphology, 0105 earth and related environmental sciences, Deep-sea fan, Sediment, Geology, Late Quaternary, Volcaniclastic, Land-to-sea transfer, 13. Climate action, Sedimentary rock
Abstract

International audience; Recent marine geophysical surveys reveal the existence of well-developed volcaniclastic deep-sea fans around La Réunion Island, Indian Ocean. The Mafate turbidite complex, located in the northwestern part of the island, is a large sedimentary system formed by two coalescent-like volcaniclastic deep-sea fans: the Mafate fan and the Saint-Denis fan. They are both connected to terrestrial rivers supplying sediment produced by erosion on the island, particularly during austral summer cyclonic floods. Through the integration of marine geophysical data (including bathymetry, backscatter multibeam sounder images, TOBI side-scan sonar images and seismic reflection profiles) and piston cores, a submarine morpho-sedimentary map of the surface architecture of the Mafate and Saint-Denis turbidite systems has been established. The systems are divided in three main domains: deep canyons in the proximal area, a channel network in the medial area, and distal depositional lobes on the abyssal sea floor. Two large sediment wave fields also formed as a result of the volcaniclastic turbidity currents. Three piston cores collected along the Mafate complex provide information on the sedimentary processes in this area over the last 25 ka. The record of turbidite events in these cores is interpreted in terms of volcanic and climatic changes that could have controlled the sediment transfer to the deep ocean.

Published
2016

3. Erosion and Volcaniclastic Sedimentation at Piton de la Fournaise: From Source to Deep Marine Environment

Author

Patrick Bachèlery, Aude Mazuel, Nathalie Babonneau, Nicolas Villeneuve, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris, Observatoire Volcanologique du Piton de la Fournaise (OVPF), Institut de Physique du Globe de Paris, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS), Patrick Bachèlery, J.-F. Lenat, Andréa Di Muro, Laurent Michon, Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), Institut de Physique du Globe de Paris (IPG Paris), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Canyon, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Sediment, Submarine canyon, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Coastal erosion, Turbidite, 13. Climate action, Erosion, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Sedimentary rock, 14. Life underwater, Sediment transport, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

International audience; With very high rainfall, steep slopes and young reliefs, La Réunion Island is renowned for its highest erosion rates worldwide. The erosion mainly occurs by rockfalls and landslides in the steep sides of the river canyons. Most sediment is transported from inland to the sea via rivers and streams. River channels are formed by incision into the basaltic pile of lava and breccia constituting the original volcanic shield. Erosion and sediment products in the largest rivers are mainly driven by the recurrence of tropical cyclones. Cyclonic conditions induce heavy rainfalls and torrential floods, causing land erosion and hyperconcentrated sediment loads in the main river mouths. The absence of coastal platform induces no sediment storage in shallow marine environment. Erosion processes onland and sediment transport to the coast, via river systems, induce direct sediment feeding of the upper submarine slope and canyon heads. The morphology of the submarine flanks of Piton de la Fournaise is rough and steep. Different submarine features were identified as debris avalanches deposits, erosive canyons and volcanic constructions. This chapter proposes a synthesis of morphological and sedimentological data on Piton de la Fournaise volcano, onland and offshore, at different scales. It describes the relationships between the main erosional structures onland and major submarine sedimentary systems. Combining onland erosion, sediment transport on the submarine slopes and sediment deposition in the deep-sea allow a better understanding of the transfer of volcaniclastic material on oceanic shield-volcanoes. The morphology of onland and submarine slopes of Piton de la Fournaise suggests two domains, distinguished by the maturity of land-to-sea sediment transfers, directly related to the maturity of hydrological networks onland. The first domain corresponds to limited land-to-sea transfer, with no hydrographic network, as observed on the volcanic rift-zones. The coastal area forms a rocky promontory and only coastal erosion of recent fragmented volcanic rocks, produces sediments in the upper submarine slope. Submarine instabilities, scarps, and local erosional canyons are superficial and discontinuous on the slope. The second domain corresponds to high-efficient land-to-sea sediment transfer, characterised by a direct connection between river mouths and submarine canyon heads (as for “Rivière des Remparts”). The submarine sedimentary systems are well-developed with continuous canyons, feeding deep-sea fans at the base of the slope. These volcaniclastic deep-sea fans are characterised by sandy lobe accumulation fed by small channels and are typically interpreted as the result of turbidite processes and deposits.

Published
2016

4. Processes controlling a volcaniclastic turbiditic system during the last climatic cycle: Example of the Cilaos deep-sea fan, offshore La Réunion Island

Author

Patrick Bachèlery, Marie Salpin, Béatrice de Voogd, E. Sisavath, Samuel Toucanne, Luc Beaufort, Aude Mazuel, Stephan J. Jorry, Laurent Emmanuel, Nathalie Babonneau, Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), Laboratoire Environnements Sédimentaires (LES), 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), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Modélisation et d'Imagerie en Géosciences de Pau (MIGP), Institut national des sciences de l'Univers (INSU - CNRS)-TotalFinaElf-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de La Réunion (UR)-Institut de Physique du Globe de Paris, Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Modélisation et Imagerie en Géosciences - Pau (MIGP), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-TotalFinaElf-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), and Institut de Physique du Globe de Paris-Université de La Réunion (UR)

Subjects
La Réunion Island, 010504 meteorology & atmospheric sciences, Stratigraphy, Pyroclastic rock, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Volcaniclastic system, Sedimentary depositional environment, Paleontology, La Reunion Island, Geomorphology, Indian Ocean, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Cirque, Sediment, Geology, Massif, Late Quaternary, Turbidites, Turbidite, Volcano, 13. Climate action, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy
Abstract

International audience; The present study focused on turbidite sedimentation in the Cilaos turbidite system, a volcaniclastic deep-sea fan recently recognized offshore La Réunion Island. A set of piston cores was collected in order to establish the stratigraphy of this fan and to examine the processes controlling the turbidite sedimentation off the Cilaos cirque (Piton des Neiges volcanic massif) over the last climatic cycle. Two main phases of turbidite activity were identified, during the ca 140-127 ka and 30-0 ka periods, coinciding with the two last glacial-interglacial transitions (i.e., Terminations II and I). In addition to changes in climate and eustatic sea-level, these periods coincide with a low effusive volcanic activity of the Piton des Neiges volcano. The high erosional rates identified in the Cilaos cirque during these intervals of both low effusive volcanic activity and enhanced rainfall level are probably the main driver of sediment supply to the deep‐sea depositional system. These new findings also highlight the important capacity of volcaniclastic turbidite systems to record rapid paleoenvironmental changes.

Published
2012

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