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1. Changes in marine sedimentation patterns in the northeastern South China Sea in the past 35,000 years

Author

Kuan-Ting Chen, Shu-Kun Hsu, Andrew Tien-Shun Lin, Chih-Chieh Su, Nathalie Babonneau, Gueorgui Ratzov, Serge Lallemand, Pi-Chun Huang, Lien-Kai Lin, Hsiao-Shan Lin, Ching-Hui Tsai, Jing-Yi Lin, and Song-Chuen Chen

Subjects
Geology, QE1-996.5, Environmental sciences, GE1-350
Abstract

Abstract In the continental margin of the northeastern South China Sea, the sea level fluctuations since the Last Glacial Maximum have profoundly impacted the sedimentary environment. Our sub-bottom profiler data show a sedimentation process change from deposition to erosion during the Last Glacial Maximum. After the widespread erosion, the sedimentation process returned depositional throughout the Holocene, probably due to the rise of the sea level. This sedimentary process results in a widespread sedimentary unconformity in the continental slope, providing a benchmark for the end of the Last Glacial Maximum. Analyzing the sediment cores, we affirm that the change in current intensity is the primary factor controlling the sedimentary environments. The current intensities strengthened during the eustatic lowstand and weakened during the highstand periods, leading to alternating erosional and depositional processes. The widespread distribution of the erosive surface represents a regional-scale change in the sedimentary environment instead of a local event.

Published
2024
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2. Changes in the particulate organic carbon pump efficiency since the Last Glacial Maximum in the northwestern Philippine Sea

Author

Pierrick Fenies, Maria-Angela Bassetti, Natalia Vazquez Riveiros, Sze Ling Ho, Yuan-Pin Chang, Ludvig Löwemark, Florian Bretonnière, Nathalie Babonneau, Gueorgui Ratzov, Shu-Kun Hsu, and Chih-Chieh Su

Subjects
Bottom, Pore water oxygenation, Paleoproductivity, Typhoon, Benthic foraminifera, Monsoon, Geography. Anthropology. Recreation, Archaeology, CC1-960
Abstract

Changes in bottom and pore water oxygenation over glacial – interglacial cycles have influenced the ocean's capacity to store particulate organic carbon regardless of its source, either the marine primary productivity or the continent-to-ocean transfer of terrestrial organic matter. In the Philippine Sea, east off Taiwan, despite being currently oligotrophic, the enhanced East Asian Winter Monsoon during the Last Glacial Maximum and the Heinrich Stadial 1 might have altered the nutrient budget in surface waters by providing nutrients from the Eurasian loess dust and deepening the vertical mixing, bringing nutrients from the nutrient-enriched Kuroshio Current subsurface waters to the surface. During the deglaciation, previous studies also suggest an overall weakening of the marine biological pump during the Heinrich Stadial 1, and the rise in sea level is expected to have led to a global significant decline in the ability of continents to bury their particulate organic carbon in marine sediments. However, changes in the continent-ocean transfer of terrestrial organic matter and on the marine biological pump around Taiwan remain poorly constrained.In the present study, we have thus aimed to reconstruct bottom – pore water oxygenation, past marine primary productivity and continental-ocean transfer of terrestrial particulate organic carbon to the ocean since the end of the Last Glacial Maximum, in order to better constrain the ability of marine sediments to capture atmospheric carbon over the past 20,000 years. To this end, sediment core MD18-3523 has been recovered from a levee of Hoping Canyon, north-east of Taiwan, in the Ryukyu forearc basin. The reconstructions were made possible by the application of multivariate statistics and transfer functions on benthic foraminiferal assemblages, by the measurement of total organic carbon concentration and by the investigation of chemical element ratios obtained from X-ray fluorescence (XRF).We observed a transition across the Bølling–Allerød and the Younger Dryas from suboxic-dysoxic bottom – pore waters during Heinrich Stadial 1 to oxic-suboxic during the Holocene, and revealed an increase in marine primary productivity during Heinrich Stadial 1 in all probability due to intensified East Asian Winter Monsoon winds. We have also identified periods of enhanced terrestrial particulate organic carbon transfer to the ocean driven by short-lived extreme events, most likely typhoons, during the Bølling–Allerød, at the beginning of the Early Holocene and the end of the Late Holocene, when the typhoon dynamics affecting Taiwan were intensified. Overall, these findings suggest an enhanced marine biological pump during the Heinrich Stadial 1 and an efficient carbon turbidity pump during the Bølling–Allerød, the Early and Late Holocene, contrasting with the western coast of Taiwan.

Published
2024
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3. Contourite on the Limpopo Corridor, Mozambique margin: Long‐term evolution, facies distribution and Plio‐Quaternary processes

Author

Nathalie Babonneau, François Raisson, Adrien Genêt, Ugo Lopes, Ruth Fierens, Elda Miramontes, Sidonie Révillon, Marina Rabineau, Laurence Droz, Deborah Belleney, Maryline Moulin, Daniel Aslanian, Geo-Ocean (GEO-OCEAN), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), TotalEnergies, Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Université de Brest (UBO)-Université de Rennes 2 (UR2)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes Université (Nantes Univ)-Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN), Nantes Université - pôle Humanités, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Humanités, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN), and Nantes Université (Nantes Univ)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Bottom current, calcarenite, drift, Stratigraphy, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, General Earth and Planetary Sciences, Geology, contourite, moat, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Mozambique, General Environmental Science
Abstract

Bottom currents are key processes that contribute to the shaping of submarine slopes, with the redistribution of sediments in contourite systems. Despite numerous recent studies on contourite systems, the complexity and diversity of these sedimentary systems are still not fully understood and often underestimated. Their understanding requires comprehensive works integrating all scales from seismic architecture to microfacies. This paper focuses on a contouritic ridge located between 2000 m and 2500 m water depth on the Mozambique margin. Bathymetry, seismic data and piston cores collected during the PAMELA-MOZ3 cruise allow a multi-scale study from large depositional geometries to sedimentary facies. At the seismic scale, the contouritic ridge show three stages of evolution with: (i) initiation and development of the drift/moat system; (ii) an intermediate stage with successive incisions and aggradations; and (iii) moat infill and drift erosion during the Plio-Quaternary. Plio-Quaternary deposits are composed of hemipelagic, turbiditic and contouritic facies filling the moat. Coarse-grained contouritic facies, dominated by planktonic foraminifera, are identified on the western flank of the ridge between the moat infill and the erosional area at the top of the ridge. They consist of condensed deposits, with sedimentation rate about 0.3 cm/ka, indicating a strong and stable bottom current that winnows away the fine-grained component. This facies could be present more generally in intermediate position between erosion and depositional areas in contourite systems. At present, the contourite system is located at the transition depth between North Atlantic Deep Water and Antarctic Intermediate Water. Trajectories of bottom currents are complex and interact with sporadic turbidity currents and anti-clockwise eddies that participate in reshaping the sea floor morphology. Although Plio-Quaternary depositional geometries indicate the end of drift/moat development, the moat filling and drift erosion are also related to bottom currents and constitute atypical contouritic sedimentation.

Published
2023

4. Sedimentary evolution and effects of structural controls on the development of the Zambezi mixed turbidite-contourite system (Mozambique channel, southwest Indian Ocean) since the Oligocene

Author

Ruth Fierens, Laurence Droz, Gwenael Jouet, Marina Rabineau, François Raisson, Nathalie Babonneau, Cécile Robin, Stephan J. Jorry, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), TotalEnergies, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and PAMELA (IFREMER)

Subjects
Zambezi turbidite system, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Stratigraphy, Late Cenozoic, Geology, Mozambique Channel, Tectonic, Oceanography, Turbidite, Contourite, Geophysics, Late cenozoic, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Economic Geology, Multichannel seismic profiles
Abstract

International audience; High-resolution multichannel seismic reflection data that spans significant parts of the Mozambique margin offshore the Zambezi River permits the study of the Oligocene to present architectural evolution of the Zambezi turbidite system. In this time frame, five major depositional units are recognized that evidence a widespread spatial and temporal occurrence of both turbiditic and contouritic sedimentation. They indicate that the sedimentary regime within the turbidite system changed from dominantly aggradational during the Oligocene to mainly erosional during Miocene to an interplay of erosional and depositional processes during the Plio-Quaternary. Different episodes of incision, linked with the Serpa Pinto, Angoche and Zambezi valleys, are recognized in the upstream portion of the Zambezi Fan and highlight a westward (anticlockwise) shift of feeding axes. The central portion of the Zambezi Valley was affected by a progressive structural doming during the Miocene. The dominance of long-lasting erosional processes generated by the continuous rise of the seabed led to a deep entrenchment of the Zambezi Valley. This tectonically-controlled over-incision is believed to be the cause of the absence of Miocene levees, and has played an important role in the stabilization of the valley at its current position. Finally, our study revealed a quasi-constant development of contourite accumulations since the Late Miocene that occur most often synchronous with turbiditic sedimentation. The present study offers unique insight into the controls and stages of development of one of the largest turbidite systems in the world and demonstrates especially its susceptibility to structural activity.

Published
2022

5. Foraminifera as a tool for the reconstruction of paleobathymetry and geohazard: A case study from Taiwan

Author

Raúl Tapia, Sicheng Le, Sze Ling Ho, Maria Angela Bassetti, In-Tian Lin, Hui-Ling Lin, Yuan-Pin Chang, Kuo-Tung Jiann, Pei-Ling Wang, Jheng-Kuan Lin, Nathalie Babonneau, Gueorgui Ratzov, Shu-Kun Hsu, and Chih-Chieh Su

Subjects
%P, downslope sediment transport, geohazard, foraminifera, Taiwan, paleobathymetry
Abstract

The calcite tests of foraminifera are an important biogenic component of marine sediments. The abundance of foraminiferal tests in marine sediments broadly varies with bathymetry, thus has been used to reconstruct paleobathymetry. It is also promising as a tracer for downslope transport triggered by earthquakes and typhoons, especially if the displaced material from shallow locality contrasts strongly with the background autochthonous sediments in terms of foraminiferal abundance, such as the ratio of benthic and planktic foraminifera termed %P. However, its applicability in sediments off Taiwan has not been assessed. Taiwan is located in the path of typhoons and at tectonic plate margins, where typhoons and earthquakes may trigger submarine geohazards. This, combined with the fact that its seafloor spans a large bathymetric range, render this region an ideal natural laboratory to evaluate the applicability of %P as a proxy for tracing submarine geohazards and bathymetry. Here we report foraminiferal abundance, %P, grain size and elemental data from 148 surface sediment samples off 6 sectors off Taiwan, namely Southern Okinawa Trough, Hoping-Nanao-Hateruma Basins, Taitung-Hualien, Hengchun Ridge, Gaoping, and Changyun Sand Ridge. Of all the hydrographic and sedimentological parameters assessed, seafloor bathymetry is the major driver of foraminiferal abundance and %P in these regions. Notably, several data points deviate from the regional %P-water depth relationship. Based on sedimentological parameters and previous studies, we posit that these outliers may have to do with local sedimentation setting. These processes include earthquake-induced sediment transport via submarine canyon in the Southern Okinawa Trough, typhoon-triggered sediment flushing in Gaoping Canyon, cross-shelf and northward advection of planktic foraminifera on the Gaoping shelf, and carbonate dissolution in deep Hateruma Basin. Off Taiwan, the %P value in sediments increases exponentially with bathymetry (R2 = 0.72), and agrees well with the global calibration obtained by combining 827 data from several regions of the global ocean. The regional %P-water depth relationship may be useful for reconstructing paleobathymetry here, albeit with an uncertainty of ~400 m that increases with bathymetry especially >2000 m. Our results also highlight the potential of the %P index as a tracer for downslope transport and lateral advection in the water column. The downcore application of %P therefore has the potential to reconstruct past geohazard events while also identify autochthonous sediment sequences that are suitable for paleoceanographic reconstruction.

Published
2022

6. Clay-mineral distribution in recent deep-sea sediments around Taiwan: Implications for sediment dispersal processes

Author

Shu Kun Hsu, Andrew Lin, Kuo-Fang Huang, Prabodha Das, Zhifei Liu, Radha Krishna Pillutla, Gueorgui Ratzov, Kalyani Nayak, Nathalie Babonneau, Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])

Subjects
Provenance, Turbidity current, 010504 meteorology & atmospheric sciences, Geochemistry, Taiwan, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, engineering.material, 010502 geochemistry & geophysics, River-fed turbidity currents, 01 natural sciences, Deep sea, chemistry.chemical_compound, Chlorite, 0105 earth and related environmental sciences, Earth-Surface Processes, Kuroshio current, Sediment, Turbidite, Clay minerals, Geophysics, chemistry, Luzon, [SDU]Sciences of the Universe [physics], Illite, engineering, Geology
Abstract

International audience; Clay-mineralogy study of Taiwanese river-mouth sediments, recent deep-water seafloor sediments around Taiwan, along with sediments collected from the Tainan shelf edge, have been investigated to access the source and transport of detrital fine-grained sediments. We determined the clay mineralogy in both hemipelagites and turbidites in the top 50 cm of the deep-sea sediment cores to infer how sediments are dispersed through river-fed turbidity currents, hypopycnal plumes, and oceanic currents. Our results show that the clay mineral assemblages in both hemipelagites and turbidites of different provinces change gradually between two major end-members: illite+chlorite and smectite. They are predominantly sourced from Taiwan and Luzon, respectively. The relative abundances of clay minerals in turbidites and hemipelagites are quite similar in most of the cores. Therefore, we argue that the adjacent turbidites and hemipelagites of a core share common detrital clay sources. We found that smectite is relatively abundant around Taiwan, indicating that the Kuroshio Current is an important transportation system, which brings smectite from Luzon. Besides, the river-related canyon systems consist dominantly of illite and chlorite, and less smectite, indicating that the smectite brought about by the Kuroshio Current is diluted by river-fed hyperpycnal and hypopycnal flows. This also implies that flood-induced turbidity currents are efficient agents for transporting Taiwan-derived sediments into the neighboring deep-sea basins.

Published
2021

7. Width variation around submarine channel bends: Implications for sedimentation and channel evolution

Author

Tania Marsset, Tim J. Wright, David M. Hodgson, Jeff Peakall, Bernard Dennielou, Nathalie Babonneau, Ricardo Silva Jacinto, and Franziska A. Palm

Subjects
Monsoon, 010504 meteorology & atmospheric sciences, Bank pull, Flow (psychology), Geology, Geometry, Lateral expansion, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Seafloor spreading, Quaternary, South Atlantic, Congo, Geochemistry and Petrology, Passive margin, Aggradation, Submarine channel, Channel morphology, Channel bank, Sedimentation, Bank erosion, 0105 earth and related environmental sciences, Communication channel
Abstract

Submarine-fan channels can build the largest sediment accumulations on Earth, but our understanding of flow and sedimentation processes related to channel evolution remains limited. Results from physical and numerical modelling predict dominantly downstream channel bend migration. However, observations and evolutionary models for aggradational submarine channels on passive margins suggest that bends are dominated by lateral expansion. This paradox may be due to limitations induced by the use of constant width channels in process studies. Constant width has been used for two reasons: partly because this is the simplest possible case, but primarily because the width variation around submarine channel bends is unknown. Channel width variations are examined from an active channel reach with 49 bends and three inactive but unfilled channel reaches with a total of 35 bends from the Congo Fan. Each bend was divided into 13 cross-sections, and for each cross-section, channel width was measured for the channel base, and at 10 m vertical increments up to the height of the channel banks. The results indicate that channels are typically wider around bend apices than around inflections. We argue that this morphology suggests that channels are controlled by bank-pull (outer bank erosion), with later deposition at the inner bend, similar to many rivers. The implications of these spatial changes in channel width around bends for sedimentation and channel evolution are explored, and we suggest that such changes may account for the contradictions between physical and numerical modelling, and seafloor observations. Integration of these channel width data with the known climate history of the Congo Fan, further suggests that the magnitude of channel width variation at bend apices may be controlled by allogenic forcing, with larger flows associated with greater width variations around bends.

Published
2021

8. Late Quaternary geomorphology and sedimentary processes in the Zambezi turbidite system (Mozambique Channel)

Author

Steven Landurain, Ruth Fierens, Stephan J. Jorry, Samuel Toucanne, Elda Miramontes, François Raisson, Nathalie Babonneau, Laurence Droz, Gwenael Jouet, Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), 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 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), Centre scientifique et Technique Jean Feger (CSTJF), TOTAL FINA ELF, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), and Unité de recherche Géosciences Marines (Ifremer) (GM)

Subjects
Zambezi turbidite system, Turbidity current, 010504 meteorology & atmospheric sciences, North Atlantic Deep Water, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Late Quaternary, 010502 geochemistry & geophysics, 01 natural sciences, Turbidite, Sedimentary depositional environment, Thalweg, Paleontology, [SDU]Sciences of the Universe [physics], Facies, Sub-bottom seismic profiles, Overbank, Sedimentary rock, Multibeam bathymetry, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 14. Life underwater, Geology, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract

International audience; The morphology and present-day sediment distribution of the Zambezi turbidite system was investigated using new bathymetric and sub-bottom profiler data as part of the PAMELA research project. The Zambezi turbidite system is composed of two depositional systems: a channelized fan (the Zambezi Fan) and a semi-confined fan (in the Intermediate Basin). The Zambezi Fan includes the Zambezi Valley, which is deeply incised in the Mozambique Channel and is more than three times as large and deep as the great Tanzanian and North Atlantic Mid-Ocean channels. The erosion in the Zambezi Valley is evidenced by its V-shaped morphology and the existence of a U-shaped thalweg affected by several generations of incisions. Based on echo facies and cores from literature, sediments of the Zambezi Fan are dominantly coarse-grained and fine-grained overbank deposits are infrequent. The distal portion of the Zambezi Fan is a main depositional area where typical transparent wedged-shape seismic bodies are interpreted as terminal lobes. Seismic facies in the Intermediate Basin are thought to represent mostly fine-grained turbidites intercalated with infrequent coarse-grained sheet-like turbidites. Hydrodynamic circulation (from surface eddies to the deep circulation of NADW) appears to have a great impact on the Mozambique Channel sedimentation and is suggested (1) to be involved in the delivery of the Zambezi River sediments along the Mozambique margin, (2) to entrain the upper suspended load of turbidity currents, contributing to the absence of fine-grained sedimentation and (3) to contribute to the erosion of the valley flanks leading to the exceptionally great dimensions of the valley

Published
2019

9. Shallow gas hydrates off southwest Taiwan and their mechanisms

Author

Ching Hui Tsai, Gueorgui Ratzov, Yuan-Pin Chang, Yin Sheng Huang, Shiao Shan Lin, Serge Lallemand, Andrew Lin, Jing Yi Lin, Kuo-Yen Wei, Nathalie Babonneau, Neng Ti Yu, Chih-Chieh Su, Shu Kun Hsu, Pai Sen Yu, Pi Chuen Huang, National Central University [Taiwan] (NCU), Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)

Subjects
010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Clathrate hydrate, Geochemistry, Of SW Taiwan, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Unconformity, Methane, chemistry.chemical_compound, MD core, Geochemistry and Petrology, Hydrate dissociation, 14. Life underwater, 0105 earth and related environmental sciences, Shallow gas hydrate, Pockmark, Authigenic, Seafloor spreading, Geophysics, chemistry, 13. Climate action, Off SW Taiwan, Ridge (meteorology), Upwelling, Geology
Abstract

We have collected two shallow gas hydrate samples at two sites having different geological settings off southwest Taiwan during the cruise MD214 in 2018. The first core site, MD18-3542, is on the South Yuan-An East Ridge at ~ 1200 m water deep, where a structural unconformity covered by fine-silt sediments appears at ~ 5.5 m below the seafloor. The second core site, MD18-3543, is close to the Good-Weather Ridge at ~ 1100 m water deep, where a gas-related pockmark structure and authigenic carbonates are present at shallow strata with fine-silt sediments near the seafloor. Sediment properties of core MD18-3542 are distinctively different above and below the layer corresponding to the unconformity. Both cores show obvious gaps or voids in the lower core halves. The core features could be linked to the dissociated methane upward migrating from deep strata. Core site settings with upwelling methane would favor the formation of shallow gas hydrates. At site MD18-3542, the shallow hydrate could be formed due to high concentration methane kept beneath the unconformity covered by fine-silt sediments. At site MD18-3543, the shallow hydrate could be formed due to an extremely high flux of upwelling methane trapped either beneath the authigenic carbonates or fine-silt sediments.

Published
2021

10. Paleoenvironmental changes, climate and anthropisation in the Western Mediterranean Sea during the 4.2 Kyr event along a North-South Transect

Author

Nathalie Combourieu-Nebout, Vincent Coussin, Yannick Miras, Aurélie Penaud, Sandra Picard Casal, Odile Peyron, Bassem Jalali, Marie-Alexandrine Sicre, Nathalie Babonneau, Antonio Cattaneo, Histoire naturelle de l'Homme préhistorique (HNHP), Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Variabilité de l'Océan et de la Glace de mer (VOG), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Unité de recherche Géosciences Marines (Ifremer) (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Université de Perpignan Via Domitia (UPVD), Université de Brest (UBO)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), and Géosciences Marines (GM)

Subjects
[SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 14. Life underwater, 15. Life on land, ComputingMilieux_MISCELLANEOUS
Abstract

The 4.2 ka event is considered a key-period of the Mediterranean climate because of its potential impact on human societies over the Holocene. Numerous records provide a detailed description on its expression in continental and marine archives (e.g. Bini et al, 2019). They generally indicate cold/dry conditions, although not uniformly expressed across the Mediterranean, and summer dryness reinforced by dry winters. Palynological data from the central Mediterranean basin show a complex response of the vegetation during this climatic event that seems to be more pronounced in the southern sites.In this study, we developed a multidisciplinary approach on two sequences collected in the Western Mediterranean Sea to insight the response of the W-Mediterranean forest along a North-South transect. The two marine records, KSGC-31 (43°N - 3°17.9’E; 60 m water depth, Gulf of Lion margin at 20 km from the coast) and MD04-2801 (36°30.99’ N - 0°30.03’ W, 2067 m water depth, 12km from the Algerian coast) were used to document regional changes in the basin between 5 and 3 kyr BP at a multi-decadal to centennial scale temporal resolution.Information derived from palynological (pollen, spores, dinocysts, microalgae and non-pollen palynomorphs) and marine proxy data (alkenone-derived SSTs, isotopes...) are combined to evaluate environmental and hydrological changes and how this relate to human activities. Our findings highlight coherent climatic patterns and time-lags along a South-North transect in the Western Mediterranean during the establishment of droughts. They also reveal the first indications of human impact in the two areas. Overall, our study shows the effectively of our approach based on cross-analysis of continental palynological and marine evidences to decipher the chronology of sequence of events embedded in multiproxy records.Bini, M., Zanchetta, G., Perşoiu, A., et al. : The 4.2 ka BP Event in the Mediterranean region: an overview, Clim. Past, 15, 555–577, https://doi.org/10.5194/cp-15-555-2019, 2019.

Published
2020

11. The Last Glacial Maximum Balearic Abyssal Plain megabed revisited

Author

Jeffrey Poort, Sebastien Garziglia, Gwenael Jouet, Sébastien Migeon, Massimo Bellucci, Cristina Caradonna, Marina Rabineau, Shray Badhani, Bernard Dennielou, Germain Bayon, Michael A. Clare, Nathalie Babonneau, Grigorii Akhmanov, Antonio Cattaneo, Laurence Droz, Estelle Leroux, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), University of Trieste, Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), Lomonosov Moscow State University (MSU), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), National Oceanography Centre [Southampton] (NOC), University of Southampton, Università degli studi di Trieste = University of Trieste, Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Abyssal plain, Sediment, Geology, Ocean Engineering, Last Glacial Maximum, Structural basin, 010502 geochemistry & geophysics, 01 natural sciences, Deep sea, Paleontology, Mediterranean sea, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Facies, Sedimentary rock, 14. Life underwater, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Water Science and Technology
Abstract

Megabeds are thick sedimentary layers extending over thousands of square kilometres in deep-sea basins and are thought to result from large slope failures triggered by major external events. Such deposits have been found in at least three areas of the Mediterranean Sea. Although their discovery dates back to the early 1980s, many questions remain concerning their initiation, source area, extent and the nature of their emplacement. One of the largest previously documented megabeds was emplaced during the Last Glacial Maximum across the Balearic Abyssal Plain, with a thickness of 8–10 m in water depths of up to 2800 m. New 3.5 kHz sub-bottom profiles and sediment cores provide greater constraints on the lateral variability of the megabed and allow it to be mapped beyond previous estimates, with a revised areal extent of 90 000– 100 000 km 2. The megabed terminations show a gradual pinchout to the west and an abrupt eastward termination against the steep Sardinia margin. The megabed presents, in seismic profiles and sediment cores, a tripartite subdivision, which most likely corresponds to the changes in flow regimes across the basin, with a central area of sandy facies and an erosional base oriented NNE–SSW; this allows renewed discussions about the sources and triggers of the megabed.

Published
2020
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12. Tectonic expression of an active slab tear from high-resolution seismic and bathymetric data offshore Sicily (Ionian Sea)

Author

Aaron Micallef, Yann Le Faou, Nathalie Babonneau, Luis M. Pinheiro, Flora Gallais, Marc-André Gutscher, Bernard Mercier de Lépinay, Stéphane Dominguez, Marzia Rovere, Giovanni Barreca, and Antonio Cattaneo

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Subduction, Active fault, Fault (geology), Sedimentary basin, 010502 geochemistry & geophysics, Strike-slip tectonics, 01 natural sciences, Seafloor spreading, Tectonics, Geophysics, Geochemistry and Petrology, Lithosphere, 14. Life underwater, Geology, Seismology, 0105 earth and related environmental sciences
Abstract

Subduction of a narrow slab of oceanic lithosphere beneath a tightly curved orogenic arc requires the presence of at least one lithospheric scale tear fault. While the Calabrian subduction beneath southern Italy is considered to be the type example of this geodynamic setting, the geometry, kinematics and surface expression of the associated lateral, slab tear fault offshore eastern Sicily remain controversial. Results from a new marine geophysical survey conducted in the Ionian Sea, using high-resolution bathymetry and seismic profiling reveal active faulting at the seafloor within a 140 km long, two-branched fault system near Alfeo Seamount. The previously unidentified 60 km long NW trending North Alfeo Fault system shows primarily strike-slip kinematics as indicated by the morphology and steep-dipping transpressional and transtensional faults. Available earthquake focal mechanisms indicate dextral strike-slip motion along this fault segment. The 80 km long SSE trending South Alfeo fault system is expressed by one or two steeply dipping normal faults, bounding the western side of a 500+ m thick, 5 km wide, elongate, syntectonic Plio-Quaternary sedimentary basin. Both branches of the fault system are mechanically capable of generating magnitude 6–7 earthquakes like those that struck eastern Sicily in 1169, 1542, and 1693.

Published
2016

13. The Congolobe project, a multidisciplinary study of Congo deep-sea fan lobe complex: Overview of methods, strategies, observations and sampling

Author

Nicolas Gayet, Karine Charlier, Mélanie Raimonet, Olivier Ragueneau, Philippe Noel, J. Le Saout, Christophe Rabouille, Florence Savignac, Laurent Toffin, Gilles Vétion, Ming-Yi Sun, Lucie Pastor, Perrine Cruaud, S. Bourgeois, Anne Godfroy, Françoise Lesongeur, F. Toussaint, Julie Tourolle, François Baudin, Olivier Mouchel, Elsa Stetten, Philippe Rodier, Audrey M. Pruski, Martine Bez, Cecile Cathalot, Martial Taillefert, Sophie Arnaud-Haond, Lara Pozzato, Rudolph Corvaisier, Laurence Méjanelle, N. Tisnerat-Laborde, Claire Croguennec, Christophe Brandily, Philippe Martinez, Jean-Claude Caprais, Arunima Sen, Bernard Dennielou, Bruno Bombled, Sandrine Bessette, C. Senyarich, Alexis Khripounoff, Karine Olu, Laurence Droz, M. Lesaout, Marie Picot, Stéphane Hourdez, Jordon S. Beckler, J. Le Bruchec, Johann Schnyder, Patricia Pignet, Nathalie Babonneau, Livio Ruffine, M. Rabiller, J.L. Reyss, P. Michalopoulos, J.-M. Jouanneau, C. Bayle, Carole Decker, Sara Teixeira, B. Ruesch, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Océan et Interfaces (OCEANIS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire Environnement Profond (LEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Evolution et Modélisation des Bassins Sédimentaires (EMBS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), Unité de recherche Géosciences Marines (Ifremer) (GM), Laboratoire de microbiologie des environnements extrêmophiles (LM2E), Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-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), School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], Laboratoire d'Ecogéochimie des environnements benthiques (LECOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Adaptation et Biologie des Invertébrés en Conditions Extrêmes (ABICE), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Hellenic Centre for Marine Research (HCMR), Department of Marine Sciences [Athens], University of Georgia [USA], Centre of Marine Sciences [Faro] (CCMAR), University of Algarve [Portugal], Géochrononologie Traceurs Archéométrie (GEOTRAC), TOTAL-Scientific and Technical Center Jean Féger (CSTJF), TOTAL FINA ELF, ANR-11-BS56-0030,CONGOLOBE,Transfert de carbone organique et fonctionnement des écosystèmes dans les lobes terminaux de l'éventail sous-marin du Congo(2011), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Etudes des Ecosystèmes Profonds (EEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Adaptation et diversité en milieu marin (ADMM), Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre scientifique et Technique Jean Feger (CSTJF), and 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)

Subjects
Turbidity current, Continental-Margin, 010504 meteorology & atmospheric sciences, Fine sediment, Sedimentation rate, Transport, Submarine canyon, Vesicomyidae, 010502 geochemistry & geophysics, Oceanography, Turbidite, 01 natural sciences, Deep sea, Particulate Materials, Guaymas Basin, 14. Life underwater, Congo deep-sea fan, Chemosynthetic habitats, Turbidity-Current, 0105 earth and related environmental sciences, Canyon, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, ACL, Organic-Carbon Accumulation, Particle Fluxes, Estuary, Seafloor morphology, 15. Life on land, M Water Depth, 13. Climate action, Mud Volcano, [SDE]Environmental Sciences, Chemosynthetic Ecosystems, Submarine pipeline, Sedimentary rock, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Geology
Abstract

The presently active region of the Congo deep-sea fan (around 330,000 km(2)), called the terminal lobes or lobe complex, covers an area of 2500 km(2) at 4700-5100 m water depth and 750-800 km offshore. It is a unique sedimentary area in the world ocean fed by a submarine canyon and a channel-levee system which presently deliver large amounts of organic carbon originating from the Congo River by turbidity currents. This particularity is due to the deep incision of the shelf by the Congo canyon, up to 30 km into the estuary, which funnels the Congo River sediments into the deep-sea. The connection between the river and the canyon is unique for major world rivers. In 2011, two cruises (WACS leg 2 and Congolobe) were conducted to simultaneously investigate the geology, organic and inorganic geochemistry, and micro- and macro-biology of the terminal lobes of the Congo deep-sea fan. Using this multidisciplinary approach, the morpho-sedimentary features of the lobes were characterized along with the origin and reactivity of organic matter, the recycling and burial of biogenic compounds, the diversity and function of bacterial and archaeal communities within the sediment, and the biodiversity and functioning of the faunal assemblages on the seafloor. Six different sites were selected for this study: Four distributed along the active channel from the lobe complex entrance to the outer rim of the sediment deposition zone, and two positioned cross-axis and at increasing distance from the active channel, thus providing a gradient in turbidite particle delivery and sediment age. This paper aims to provide the general context of this multidisciplinary study. It describes the general features of the site and the overall sampling strategy and provides the initial habitat observations to guide the other in-depth investigations presented in this special issue. Detailed bathymetry of each sampling site using 0.1-1 m resolution multibeam obtained with a remotely operated vehicle (ROV) shows progressive widening and smoothing of the channel-levees with increasing depth and reveals a complex morphology with channel bifurcations, erosional features and massive deposits. Dense ecosystems surveyed in the study area gather high density clusters of two large-sized species of symbiotic Vesicomyidae bivalves and microbial mats. These assemblages, which are rarely observed in sedimentary zones, resemble those based on chemosynthesis at cold-seep sites, such as the active pockmarks encountered along the Congo margin, and share with these sites the dominant vesicomyid species Christineconcha regab. Sedimentation rates estimated in the lobe complex range between 0.5 and 10 cm yr(-1), which is 2-3 orders of magnitude higher than values generally encountered at abyssal depths. The bathymetry, faunal assemblages and sedimentation rates make the Congo lobe complex a highly peculiar deep-sea habitat driven by high inputs of terrigenous material delivered by the Congo channel-levee system. (c) 2016 Elsevier Ltd. All rights reserved. ZAIANGO ANR Congolobe (ANR Blanc SIMI5-6) [11 BS56 030] IFREMER CEA through LSCE U.S. National Science Foundation [OCE-0831156] info:eu-repo/semantics/acceptedVersion

Published
2017

14. Evidence and age estimation of mass wasting at the distal lobe of the Congo deep-sea fan

Author

Julie Le Bruchec, François Baudin, Jean-Claude Caprais, Germain Bayon, Christophe Brandily, Claire Croguennec, Christophe Rabouille, Claire Bollinger, Livio Ruffine, Vivien Guyader, Nathalie Babonneau, Laurence Droz, Bernard Dennielou, Yoan Germain, Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Evolution et Modélisation des Bassins Sédimentaires (EMBS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Environnement Profond (LEP), Etudes des Ecosystèmes Profonds (EEP), 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 des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Unité de recherche Géosciences Marines (Ifremer) (GM), Département des Environnements Profonds, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)

Subjects
chemistry.chemical_classification, Turbidity current, 010504 meteorology & atmospheric sciences, Sediment, Mass wasting, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Diagenesis, Sedimentary depositional environment, chemistry, 13. Climate action, Anaerobic oxidation of methane, [SDE]Environmental Sciences, Organic matter, Sedimentary rock, Geology, 0105 earth and related environmental sciences
Abstract

International audience; On continental margins, sulfate reduction occurs within the sedimentary column. It is coupled with the degradation of organic matter and the anaerobic oxidation of methane. These processes may be significantly disturbed by sedimentary events, leading to transient state profiles for the involved chemical species. Yet, little is known about the impact of turbidity currents and mass wasting on the migration of chemical species and the redox reactions in which they are involved. Due to its connection to the River, the Congo deep-sea fan continuously receives huge amount of organic matter-rich sediments primarily transported by turbidity currents, which impact on the development of the associated ecosystems (Rabouille et al., 2016). Thus, it is well suited to better understand causal relationships between sedimentary events and fluid flow path, with consequences on the zonation of early diagenesis sequences. Here, we combined sedimentological observations with geochemical analyses of pore-water and sediment samples to explore how sedimentary instabilities affected the migration of methane and the distribution of organic matter within the sedimentary column. The results unveiled mass wasting processes affecting recent turbiditic and pelagic deposits, and are interpreted as being slides/ slumps and debrites. Two slides were responsible for the exhumation of an organic matter-rich sedimentary block of more than 5 m thick and the movement of a methane-rich sedimentary block, while turbidity currents enable the intercalation of sandy intervals within a pelagic clay layer. The youngest slide promoted the development of two Sulfate Methane Transition Zones (SMTZ), and may have possibly triggered a lateral migration of methane. Numerical simulation of the sulfate profile indicates that the youngest sedimentary event has occurred around a century ago. Our study emphasizes that turbidity currents and sedimentary instabilities can significantly affect the transport paths and the distribution of both methane and organic matter in the terminal lobe complex, with consequences on geochemical zonation of the sequential early diagenetic processes within the sedimentary column.

Published
2017

15. Turbidite chronostratigraphy off Algiers, central Algerian margin: A key for reconstructing Holocene paleo-earthquake cycles

Author

Gueorgui Ratzov, Abdelkarim Yelles-Chaouche, Tassadit Lateb, Nathalie Babonneau, Roza Si Bachir, Antonio Cattaneo, Jacques Déverchère, 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), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Astronomie Astrophysique et Géophysique (CRAAG), IFREMER Centre de Brest (IFREMER), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and 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)

Subjects
Turbidity current, 010504 meteorology & atmospheric sciences, Algerian margin, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Paleoseismology, Active fault, 010502 geochemistry & geophysics, Oceanography, Turbidite, 01 natural sciences, Geochemistry and Petrology, 14. Life underwater, Chronostratigraphy, Holocene, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Continental shelf, Geology, Marine paleoseismology, 13. Climate action, Facies, Seismology
Abstract

International audience; Northern Algeria is threatened by moderate to large magnitude earthquakes resulting from the slow convergence between the African and European plates. Main active faults are located offshore along the Algerian coast, as exemplified by the 2003 Mw 6.8 Boumerdès earthquake. This event triggered numerous and widespread turbidity currents over ∼ 150 km along strike in the Algerian basin (reaching 2800 m of water depth) and demonstrates the multi-source and multi-path characteristics of earthquake-triggered turbidity flows along this margin segment.We rely on the sedimentological analysis of five cores located at the toe of the Algiers margin, close to the 2003 cable break sites, to explore the potential for Holocene turbidite paleoseismology. Radiocarbon measurements provide age models for hemipelagic sediments. Based on sedimentary facies identification, analysis of depositional sequences (stacking pattern) and a stratigraphic framework established by age models, a first correlation of turbidites between the 5 cores is attempted. The number of turbidites is constant at the base of the continental slope and decreases seawards (over 80 km away from the coast). From turbidite correlations, 36 synchronous events are identified along the Algiers margin segment over the last 9 kyr, and are tentatively interpreted as seismically triggered, providing a 250 yr mean recurrence interval.The main historical earthquakes in the Algiers area (2003, 1716 and 1365 CE) reasonably correlate with three out of the four last turbidites, strengthening the hypothesis that turbidites are suitable markers for Holocene paleoseismology. Recurrence intervals of turbidites range between 50 and 900 yr, defining quiescence periods exceeding 450 yr. Three quiescence periods lasting about 800, 1400 and 500 yr (7–6.2 ka BP, 5.4–4 ka BP, and 1.5–1 ka BP, respectively) support irregular earthquake cycling. Earthquake-triggered turbidites are more frequent in the study area than in the western adjacent margin segment (offshore El Asnam). This higher frequency could arise from the close location of the seismogenic faults beneath the continental slope, whereas they are located several tenths of kilometers onland in the El Asnam area, implying less instabilities of the submarine slope.

Published
2017

16. Origin and chronology of the Augias deposit in the Ionian Sea (Central Mediterranean Sea), based on new regional sedimentological data

Author

Nathalie Babonneau, Marc-André Gutscher, Antonio Cattaneo, L. San Pedro, Laboratoire Géosciences Océan (LGO), Université de Brest (UBO)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Inconnu, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Seiche, Turbidity current, 010504 meteorology & atmospheric sciences, Augias deposit, Submarine canyon, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Sedimentary depositional environment, Paleontology, Mediterranean sea, Geochemistry and Petrology, Homogenite, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, 14. Life underwater, Geomorphology, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Continental shelf, Abyssal plain, Geology, Ionian Sea, Megaturbidite, Submarine paleoseismology, Sedimentary rock, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology
Abstract

In the Ionian Sea (Central Mediterranean Sea), several thick acoustically transparent layers are present including the Augias deposit. The Augias deposit is the most recent, thick layer covering the entire floor of the Ionian Abyssal Plain with an average thickness of 10–12 m and a maximum thickness of up to 24 m in the Sirte Abyssal Plain. This deposit has also been observed in several adjacent smaller basins in waters deeper than 3000 m. Its estimated volume is > 65 km3. There are multiple plausible hypotheses regarding its age and triggering event, which include the 1600 BC Santorini volcanic caldera collapse, the 365 AD Crete M 8.5 earthquake and other smaller earthquakes such as the 374 AD Calabria M 6.3 earthquake and the 361 AD Sicily M 6.6 earthquake. Understanding the cause of this mass-transport deposit is crucial for improving the natural hazard assessment of a vast area between southern Italy and western Greece. In this study, we propose a new interpretation of the Augias deposit in terms of sedimentary processes and origin, based on sediment cores collected in the NW Ionian Sea during the CIRCEE cruise onboard R/V Le Suroit in October 2013. The sedimentological analysis of seven piston cores reveals three sedimentary facies corresponding to the Augias deposit: 1) “homogenite”, 2) “megaturbidite” and 3) “thick sandy turbidite”. These sedimentary facies are distributed within specific morpho-tectonic regions as defined by newly acquired bathymetric data, indicating a strong control by transport and depositional processes. Sixteen radiocarbon dates obtained above and below the Augias deposit indicate a possible time window of about 500 years. This means that we cannot definitively prove a link to the 365 AD Crete earthquake, but we regard it as the most likely trigger. Other depositional models may be plausible, but here we propose a sequence of events as follows: (1) earthquake shock and possible triggering of submarine mass flow in the eastern part of the Ionian Sea (western Hellenic subduction zone); (2) tsunami waves amplified by the confined morphology of the Sicily and Calabria continental shelves inducing an intense re-suspension of fine-grained sediment and massive destabilization at the heads of submarine canyons triggering turbidity currents; (3) gravity driven downslope transport of suspended sediment toward the deep basin and decantation; and (4) a final stage of decantation from seiche waves forming the majority of the homogenite facies in the Ionian Abyssal Plain.

Published
2017

17. Morphology, structure, composition and build-up processes of the active channel-mouth lobe complex of the Congo deep-sea fan with inputs from remotely operated underwater vehicle (ROV) multibeam and video surveys

Author

Cédric Bonnel, Martine Bez, Bruno Savoye, Laurence Droz, Morgane Le Saout, Yohan Saout, Christophe Rabouille, Marie Picot, Nathalie Babonneau, Céline Jacq, Karine Olu, Bernard Dennielou, Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Domaines Océaniques (LDO), 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), Géoazur (GEOAZUR 7329), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Fluides Complexes et leurs Réservoirs (LFCR), TOTAL FINA ELF-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Unité de recherche Géosciences Marines (Ifremer) (GM), Département d'information médicale [Montpellier], Centre Hospitalier Régional Universitaire [Montpellier] (CHRU Montpellier), TOTAL S.A., TOTAL FINA ELF, Laboratoire Environnement Profond (LEP), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Océan et Interfaces (OCEANIS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), IFREMER, 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), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Centre scientifique et Technique Jean Feger (CSTJF), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), 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), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Etudes des Ecosystèmes Profonds (EEP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-TOTAL FINA ELF, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)

Subjects
Turbidity current, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Mass wasting, Turbidite, Seismic, 010502 geochemistry & geophysics, Oceanography, Debrite, 01 natural sciences, Abyssal zone, medicine, River mouth, Angola basin, Lobe, Bathymetry, Slide, 14. Life underwater, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Congo deep-sea fan, Lobe complex, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Slump, Abyssal plain, Channel, Sediment core, medicine.anatomical_structure, Angola Basin, ROV, [SDU]Sciences of the Universe [physics], [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Channel-Lobe Transition Zone, Geology
Abstract

The detailed structure and composition of turbiditic channel-mouth lobes is still largely unknown because they commonly lie at abyssal water depths, are very thin and are therefore beyond the resolution of hull-mound acoustic tools. The morphology, structure and composition of the Congo turbiditic channel-mouth lobe complex (90×40 km; 2525 km 2 ) were investigated with hull-mounted swath bathymetry, air gun seismics, 3.5 kHz sub-bottom profiler, sediment piston cores and also with high-resolution multibeam bathymetry and video acquired with a Remote Operating Vehicle (ROV). The lobe complex lies 760 km off the Congo River mouth in the Angola abyssal plain between 4740 and 5030 m deep. It is active and is fed by turbidity currents that deposit several centimetres of sediment per century. The lobe complex is subdivided into five lobes that have prograded. The lobes are dominantly muddy. Sand represents ca. 13% of the deposits and is restricted to the feeding channel and distributaries. The overall lobe body is composed of thin muddy to silty turbidites. The whole lobe complex is characterized by in situ mass wasting (slumps, debrites). The 1-m-resolution bathymetry shows pervasive slidings and block avalanches on the edges of the feeding channel and the channel mouth indicating that sliding occurs early and continuously in the lobe build-up. Mass wasting is interpreted as a consequence of very-high accumulation rates, over-steepening and erosion along the channels and is therefore an intrinsic process of lobe building. The bifurcation of feeding channels is probably triggered when the gradient in the distributaries at the top of a lobe becomes flat and when turbidity currents find their way on the higher gradient on the lobe side. It may also be triggered by mass wasting on the lobe side. When a new lobe develops, the abandoned lobes continue to collect significant turbiditic deposits from the feeding channel spillover, so that the whole lobe complex remains active. A conceptual lithostratigraphic model is proposed for five morpho-sedimentary environments: lobe rims, lobe body, distributaries, levees, feeding channel. This study shows that high-resolution bathymetry ROV observations are necessary to fully understand the build-up processes of modern channel-mouth lobes.

Published
2017

18. 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

19. 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

20. Seismic stratigraphy of the NW Moroccan Atlantic continental shelf and Quaternary deformation at the offshore termination of the southern Rif front

Author

Brigitte Van Vliet Lanoe, Pascal Roy, Marc-André Gutscher, Mohamed Sahabi, Nissrine Maad, Marina Rabineau, M. Hssain, and Nathalie Babonneau

Subjects
Global and Planetary Change, geography, geography.geographical_feature_category, Outcrop, Continental shelf, Fault (geology), Neogene, Nappe, Tectonics, General Earth and Planetary Sciences, Sequence stratigraphy, Quaternary, Geology, Seismology
Abstract

A recent high resolution seismic survey was carried out along the North-West Moroccan Atlantic continental shelf to perform sequence stratigraphy and to better understand the link between the onshore observations across the western termination of the Rif front and the multibeam bathymetric data previously collected across the Gulf of Cadiz. Seismic interpretation clearly shows evidence of deformation affecting the Pleistocene sedimentary cover. This is mainly located between the Lalla Zahra ridge and the Neogene nappes that outcrop at the seabed to the North of Larache, where the identified structures bound the upper part of a gravitationally spreading lobe and are interpreted to be developed by activation of the major tectonic structures located at the southern front of the Rif Cordillera. The offshore extension of the Lalla Zahra Ridge is characterised by an east-west trending major folded and faulted corridor. This structure marks the active front of Prerifan area and corresponds to a major Quaternary kinematic boundary in the western prolongation of the ENE-WSW trending Jebha fault.

Published
2010

21. Holocene turbidites record earthquake supercycles at a slow-rate plate boundary

Author

Antonio Cattaneo, Nathalie Babonneau, Jacques Déverchère, K. Yelles, Gueorgui Ratzov, Françoise Courboulex, Rabah Bracene, 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), Unité de recherche Géosciences Marines (Ifremer) (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Centre de Recherche en Astronomie Astrophysique et Géophysique (CRAAG), Sonatrach Exploration, Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), European Project: ENV2013 6.4-3,ASTARTE, Géosciences Marines (GM), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Plate tectonics, Seismic hazard, 13. Climate action, Interplate earthquake, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Slow rate, Geology, Sedimentary rock, Holocene, Seismology, Historical record, Turbidite
Abstract

Maradja and Prisme cruises; International audience; Ongoing evidence for earthquake clustering calls for records of numerous earthquake cycles to improve seismic hazard assessment, especially where recurrence times overstep historical records. We show that most turbidites emplaced at the Africa-Eurasia plate boundary off west Algeria over the past ∼8 k.y. correlate across sites fed by independent sedimentary sources, requiring a regional trigger. Correlation with paleoseismic data inland and ground motion predictions support that M ∼7 earthquakes have triggered the turbidites. The bimodal distribution of paleo-events supports the concepts of earthquake supercycles and rupture synchronization between nearby faults: 13 paleo-earthquakes underpin clusters of 3–6 events with recurrence intervals of ∼300–600 yr, separated by periods of quiescence of ∼1.6 k.y. without major events on other faults over the study area. This implies broad phases of strain loading alternating with phases of strain release. Our results suggest that fault slip rates are time dependent and call for revising conventional seismic hazard models

Published
2015

22. Morphogenesis of Congo submarine canyon and valley: implications about the theories of the canyons formation

Author

Stéphane Raillard, Jean-Noël Ferry, Nathalie Babonneau, Thierry Mulder, and Olivier Parize

Subjects
Canyon, geography, geography.geographical_feature_category, Turbidity current, Submarine canyon, Turbidite, West africa, Sedimentary depositional environment, Paleontology, Sequence (geology), Geophysics, Geomorphology, Geology, Earth-Surface Processes
Abstract

The bottom and edges of the Congo submarine canyon are made of deposits which show morphologies of superposed terraces associated with lense side slope. Using 3D seismic, 3.5 kHz acoustic profiles and core datas, these geometries are interpreted as being mainly the result of the polyphase processes due to the activity of turbidity currents. All the turbidite deposits located below the canyon floor and the actual Congo fan belong to a unique depositional sequence which begun at the early Pliocene. Probably, this sequence has been initiated by an important uplift of the West Africa margin.

Published
2004

23. Volcaniclastic sedimentation on the submarine slopes of a basaltic hotspot volcano: Piton de la Fournaise volcano (La Réunion Island, Indian Ocean)

Author

Francky Saint-Ange, Stephan J. Jorry, Laurent Michon, Nathalie Babonneau, Patrick Bachèlery, Geological Survey of Canada [Dartmouth] (GSC Atlantic), Geological Survey of Canada - Office (GSC), Natural Resources Canada (NRCan)-Natural Resources Canada (NRCan), Department of Oceanography [Halifax] (DO), Dalhousie University [Halifax], Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), 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), 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 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), Ifremer 'sedimentary systems' project (PJ2207), Université de La Réunion (UR)-Institut de Physique du Globe de Paris, 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), Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)

Subjects
landslide, La Réunion Island, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Pyroclastic rock, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Paleontology, Geochemistry and Petrology, La Reunion Island, Hotspot (geology), [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, 14. Life underwater, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Geomorphology, 0105 earth and related environmental sciences, Basalt, geography, geography.geographical_feature_category, Volcanic arc, debris avalanche, Geology, erosion, volcano, Volcano, 13. Climate action, Subaerial, Facies, Sedimentary rock, turbidites
Abstract

International audience; Volcaniclastic successions are well-described in volcanic arc setting but rare in hotspot environments. The present work proposes a facies model of volcaniclastic sedimentation related to basaltic hotspot volcanoes as exemplified by the Piton de la Fournaise volcano (La Réunion Island). The facies model is based on a multi-scale approach combining high-resolution multibeam and backscatter data, deep-water photographs, side scan imagery and Kullenberg piston cores. Data show that a wide range of gravity flows and erosional features develop in the active volcaniclastic sedimentary system. Coastal and submarine instabilities are the main processes shaping the volcano's submarine morphology. Meanwhile, the evolution and dynamics of the sedimentary system are strongly linked with the morpho-structural evolution of the subaerial part of the volcano. The proposed model is characterized by a cyclic succession of stages: (1) a growing stage during which sedimentary activity is mainly restricted to proximal and mid-slope areas; (2) a collapse stage that entirely reshapes the morphology of the submarine slopes; and (3) an erosional stage related to a slow down of volcanic activity, enabling the development of large deep-sea fans.

Published
2013

24. 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

25. Searching for the seafloor signature of the 21 May 2003 Boumerdès earthquake offshore central Algeria

Author

Jacques Déverchère, A. Boudiaf, Antonio Cattaneo, B. Mercier de Lépinay, G. Dan-Unterseh, K. Yelles, Gueorgui Ratzov, Rabah Bracene, Nathalie Babonneau, Unité de recherche Géosciences Marines (Ifremer) (GM), 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), FUGRO FRANCE, FUGRO, Centre de Recherche en Astronomie Astrophysique et Géophysique (CRAAG), Sonatrach Exploration, Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université des Sciences, Université Montpellier 2 - Sciences et Techniques (UM2), ANR-05-CATT-0005,ISIS,ISIS : Instabilité des pentes sous-marines dans les zones de forte activité sisimique : rupture et courant de turbidité(2005), Géosciences Marines (GM), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Turbidity current, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Paleoseismology, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], 010502 geochemistry & geophysics, Fault scarp, 01 natural sciences, lcsh:TD1-1066, margin, northern algeria, lcsh:Environmental technology. Sanitary engineering, turbidity current, lcsh:Environmental sciences, zemmouri earthquake, 0105 earth and related environmental sciences, sedimentary processes, lcsh:GE1-350, geography, geography.geographical_feature_category, cascadia subduction zone, gps, Continental shelf, lcsh:QE1-996.5, lcsh:Geography. Anthropology. Recreation, western mediterranean sea, Seafloor spreading, boundary, Turbidite, lcsh:Geology, lcsh:G, submarine landslides, 13. Climate action, General Earth and Planetary Sciences, Submarine pipeline, Geology, Seismology, Submarine landslide
Abstract

Shaking by moderate to large earthquakes in the Mediterranean Sea has proved in the past to potentially trigger catastrophic sediment collapse and flow. On 21 May 2003, a magnitude 6.8 earthquake located near Boumerdès (central Algerian coast) triggered large turbidity currents responsible for 29 submarine cable breaks at the foot of the continental slope over ~150 km from west to east. Seafloor bathymetry and backscatter imagery show the potential imprints of the 2003 event and of previous events. Large slope scarps resulting from active deformation may locally enhance sediment instabilities, although faults are not directly visible at the seafloor. Erosion is evident at the foot of the margin and along the paths of the numerous canyons and valleys. Cable breaks are located at the outlets of submarine valleys and in areas of turbiditic levee overspilling and demonstrate the multi-source and multi-path character of the 2003 turbiditic event. Rough estimates of turbidity flow velocity are not straightforward because of the multiple breaks along the same cable, but seem compatible with those measured in other submarine cable break studies elsewhere. While the signature of the turbidity currents is mostly erosional on the continental slope, turbidite beds alternating with hemipelagites accumulate in the distal reaches of sediment dispersal systems. In perspective, more chronological work on distal turbidite successions offshore Algeria offers promising perspectives for paleoseismology reconstructions based on turbidite dating, if synchronous turbidites along independent sedimentary dispersal systems are found to support triggering by major earthquakes. Preliminary results on sediment core PSM-KS23 off Boumerdès typically show a 800-yr interval between turbidites during the Holocene, in accordance with the estimated mean seismic cycle on land, even if at this stage it is not yet possible to prove the earthquake origin of all the turbidites.

Published
2012

26. Morphology and sedimentary architecture of a modern volcaniclastic turbidite system: The Cilaos fan, offshore La Réunion Island

Author

Bruno Savoye, Béatrice de Voogd, E. Sisavath, Francky Saint-Ange, Christine Deplus, Patrick Bachèlery, Stephan J. Jorry, Nathalie Babonneau, 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), 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), Geological Survey of Canada [Dartmouth] (GSC Atlantic), Geological Survey of Canada - Office (GSC), Natural Resources Canada (NRCan)-Natural Resources Canada (NRCan), Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Modélisation et Imagerie en Géosciences - 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), 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), and 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)

Subjects
010504 meteorology & atmospheric sciences, volcaniclastic, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Hemipelagic sediment, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Paleontology, Geochemistry and Petrology, La Reunion Island, 14. Life underwater, Geomorphology, 0105 earth and related environmental sciences, Canyon, geography, geography.geographical_feature_category, Alluvial fan, Abyssal plain, Sediment, Geology, Turbidite, turbidite, deep-sea fan, Sedimentary rock, Submarine landslide
Abstract

Recent oceanographic surveys revealed the existence of five volcaniclastic deep-sea fans off La Reunion Island. The Cilaos fan is a large volcaniclastic submarine fan, connected to rivers that episodically experience torrential floods through a narrow and steep shelf-slope system. New piston cores presented in this study together with echosounder profiles give new insight into the evolution, of this extensive and sand-rich turbidite system. The Cilaos fan extends over 15,000 km(2) on an abyssal plain and is compartmentalized by topographic highs. Located southwest of the island, the sedimentary system consists of a canyon area and a deep sea fan divided into a proximal and a distal fan. The proximal fan is characterized by its wide extent and coarse-grained turbidites. The distal fan is characterized by elongated structures and fine-grained turbidites. A detailed morphological study of the fan which includes the analysis of swath bathymetry, backscatter, echosounder, and piston core data shows that the Cilaos fan is a complex volcaniclastic deep-sea fan, highly influenced by preexisting seafloor irregularities. The canyons and the slope area show a complex and evolving sediment feeding system with a direct sediment input by the river and irregular sediment supply by submarine landslide. Three main construction stages are identified for this system: (1) an old incision phase of the channels forming wide turbidites extending over the entire distal fan; (2) a period of no or low activity characterized by a thick layer of hemipelagic mud; and (3) a local reactivation of the channel in the proximal fan. Each stage seems to be linked to a different sediment source with a progressively increasing contribution of hemipelagic sediment and mud in younger stages. (C) 2011 Elsevier B.V. All rights reserved.

Published
2011

27. Self-similar long profiles of aggrading submarine leveed channels: Analytical solution and its application to the Amazon channel

Author

Gary Parker, Benoît Spinewine, Tao Sun, Nathalie Babonneau, Fonds de la Recherche Scientifique and Institute of Mechanics, Materials and Civil Engineering, Université Catholique de Louvain = Catholic University of Louvain (UCL), Exxon Mobil Exploration Co, 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), Civil and Environmental Engineering [Illinois] (CEE), University of Illinois at Urbana-Champaign [Urbana], University of Illinois System-University of Illinois System, and Department of Geology

Subjects
Atmospheric Science, Turbidity current, 010504 meteorology & atmospheric sciences, Flow (psychology), Soil Science, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Initial value problem, Geotechnical engineering, Geomorphology, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, geography, geography.geographical_feature_category, Ecology, Paleontology, Submarine, Forestry, Geophysics, Space and Planetary Science, Potential flow, Levee, Sediment transport, Geology, Communication channel
Abstract

International audience; Many submarine fans are coursed by well-defined leveed channels constructed by turbidity currents. The channels aggrade in time, typically accumulating sandy deposits in their beds and muddy deposits in their levees. Periodic channel avulsion acts to build up the fan as a whole. Here a first theory for the long profile of leveed channels is offered. The theory is based on the assumption that there exists a time period, well after channel initiation but before incipient avulsion, during which the channel and its levees are in a quasi-equilibrium state, concurrently aggrading and prograding onto the surrounding fan. The currents are assumed to deposit sand on the channel bed and mud on the levees. The formulation uses a steady uniform flow assumption and a sediment transport relation inherited from rivers and yields a partial differential equation for the evolution of the channel starting from any initial condition. For the ideal case of a channel forming on an initially unchannelized sloping fan, the theory predicts self-similar long profiles for the down-channel variation of channel bed slope, bed elevation, and width, as well as flow discharge and sand/mud discharges. The time evolution of the channel then amounts to a simple rescaling of the self-similar profile as it aggrades and progrades down fan. The theory, when tested against data from the Amazon channel of the Amazon Submarine Fan, shows encouraging comparisons. The generality and shortcomings of the model assumptions are discussed based on a comparative study of mud-rich and relatively sand-rich submarine fan systems.

Published
2011

29. Tectonic inheritance and Pliocene-Pleistocene inversion of the Algerian margin around Algiers: Insights from multibeam and seismic reflection data

Author

Jacques Déverchère, Bernard Mercier de Lépinay, Antonio Cattaneo, Azzedine Boudiaf, A. Domzig, K. Yelles, Pierre Strzerzynski, and Nathalie Babonneau

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Subduction, Continental shelf, Inversion (geology), Transform fault, 010502 geochemistry & geophysics, 01 natural sciences, Salt tectonics, Tectonics, Geophysics, Continental margin, Geochemistry and Petrology, Thrust fault, Geology, Seismology, 0105 earth and related environmental sciences
Abstract

[1] The Algerian margin has originated from the opening of the Algerian basin about 25–30 Ma ago. The central margin provides evidence for large-scale normal faults of Oligo-Miocene age, whereas transcurrent tectonics characterizes the western margin. A set of NW–SE oriented dextral transform faults was active during basin opening and divided the 600 km long central margin into segments of ∼120–150 km. The upper Miocene, Plio-Quaternary, and present-day tectonic setting is, however, compressional and supports the occurrence of a margin inversion, a process still poorly documented worldwide. We show that the central Algerian margin represents a rare example of inverted margin, where the process of subduction inception is particularly well expressed and helps understand how extensional and transtensive structures are involved in margin shortening. Using multibeam bathymetry and multichannel seismic reflection sections from the MARADJA 2003 and 2005 cruises, we evidence Pliocene-Pleistocene shortening with contrasting styles along the margin between west (Khayr Al Din bank) and east (Boumerdes-Dellys margin) of Algiers. Pre-Miocene structures such as basement highs and transform faults appear to control changes of the deformation pattern along this part of the margin, resulting in different widths, geometries, and relative positions of folds and faults. Plio-Quaternary and active blind thrust faults do not reuse Oligo-Miocene normal and transform faults during inversion, but instead grow within the continental margin (as testified for instance by the 21 May 2003 Mw 6.8 Boumerdes-Zemmouri earthquake), at the foot of the continental slope and at the northern sides of basement highs interpreted as stretched continental blocks of the rifted margin. The inherited structures of the margin appear, therefore, to determine this deformation pattern and ultimately the earthquake and tsunami sizes offshore. The complex geometry of the fault system along the Algerian margin suggests a process of initiation of subduction in its central and eastern parts.

Published
2010

30. Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Author

Bruno Savoye, Bernard Dennielou, Martine Bez, Nathalie Babonneau, Laboratoire Géodynamique et enregistrement Sédimentaire - Geosciences Marines (GM-LGS), 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), Université européenne de Bretagne - European University of Brittany (UEB), Centre scientifique et Technique Jean Feger (CSTJF), and TOTAL FINA ELF

Subjects
Canyon, geography, geography.geographical_feature_category, Turbidity current, 010504 meteorology & atmospheric sciences, Continental shelf, Sediment, Context (language use), 010502 geochemistry & geophysics, Oceanography, Turbidite, 01 natural sciences, Clastic rock, Sedimentary rock, Congo Angola margin, 14. Life underwater, Congo channel, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Geology, 0105 earth and related environmental sciences, Congo–Angola margin, Sedimentary deposits
Abstract

International audience; The Congo deep-sea fan is one of the largest fans in the world still affected by presently active turbidity currents. The present activity of deep-sea sedimentary processes is linked to the existence of a direct connection between the Congo River estuary and the Congo canyon head that allows relatively continuous sediment feeding of the deep-sea environment, in spite of a wide continental shelf (150 km). Because of this important activity in terms of sedimentary processes, the deep-sea environment of the Congo–Angola margin presents major interests concerning physical, chemical and biological studies near the seafloor. The main aim of this paper is to present the initial geological context of the BioZaire Program, showing a synthesis of the major results of the ZaïAngo Project including (1) the brief geological setting of the Congo–Angola margin, (2) the structure of the modern Congo deep-sea fan, (3) the sedimentary architecture of the recent Congo turbidite system (from the canyon to the distal lobes) and (4) the recent and present turbidite sedimentation. In order to provide useful information and advice relevant to biological and geochemical studies across the Congo sedimentary system, this article is particularly focused on the present sedimentary processes and the present activity of turbidity current along the Congo canyon and channel.

Published
2009

31. Direct observation of intense turbidity current activity in the Zaire submarine valley at 4000 m water depth

Author

Philippe Crassous, Annick Vangriesheim, Bruno Savoye, Alexis Khripounoff, Bernard Dennielou, and Nathalie Babonneau

Subjects
Turbidity current, 010504 meteorology & atmospheric sciences, Particle flux, Sediment trap (geology), 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Geomorphology, 0105 earth and related environmental sciences, Total organic carbon, Hydrology, geography, geography.geographical_feature_category, Submarine, Particle composition, Geology, Mooring, Debris, 6. Clean water, Current (stream), West equatorial Africa, Channel (geography), Zaire channel
Abstract

A large turbidity current was detected in the Zaire submarine valley at 4000 m water depth. Current meters, turbidimeter and sediment trap deployed on a mooring located in the channel axis, although they were damaged, recorded the signature of a very high energy event. An average velocity of more than 121 cm s−1 was measured 150 m above the channel floor. Coarse sand and plant debris were collected at 40 m height. The turbidity current clearly overflowed the edges of the valley as demonstrated by the large quantity of turbiditic material (464 mg organic carbon m−2 d−1) found in the sediment trap moored 13 km south from the channel axis.

Published
2003

32. THE KRAMIS DEEP-SEA FAN OFF WESTERN ALGERIA: ROLE OF SEDIMENT WAVES IN TURBIDITIC LEVEE GROWTH

Author

Nathalie Babonneau, Antonio Cattaneo, Bruno Savoye, Guy Barjavel, Jacques Déverchère, Karim Yelles, 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 Environnements Sédimentaires - Géosciences Marines (GM/LES), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Centre de Recherche en Astronomie Astrophysique et Géophysique (CRAAG), and UnivBrestBU, AdminHAL

Subjects
010504 meteorology & atmospheric sciences, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, Algerian margin, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 14. Life underwater, scours, 010502 geochemistry & geophysics, 01 natural sciences, turbidity currents, sediment waves, 0105 earth and related environmental sciences
Abstract

International audience; The Kramis deep-sea fan extends over 45 km at the base of the western Algerian continental slope between 2000 and 2550 m water depth and covers an area of approximately 1200 km2. The Kramis Fan was initiated after Messinian time, evolved during the Plio- Quaternary, and, is still active, as proved by submarine cable breaks during the 1954 Orléansville earthquake. The Kramis Fan is fed by two perpendicular canyons: the Kramis Canyon and the Khadra Canyon, merging in a single E-W-oriented channel confined at the foot of the slope. It is strongly asymmetric with a super-developed levee on the right-hand side of the channel, the Kramis Ridge. Based on recent multibeam, side-scan sonar, and sediment core data (Maradja, 2003 and 2005, Prisma, 2004, and Prisme, 2007 cruises), we describe the morphology and internal structure of the fan and particularly the sediment ridge, showing marked lateral changes in the sediment-wave morphology and their association with a series of large scours in the intermediate part of the ridge aligned in the continuity of the Khadra Canyon direction. Overall, the Kramis Ridge is formed by turbidity currents overspilling the ridge crest, which is 100 m above the channel floor, with two exceptions. In the distal part of the ridge the subdued ridge-crest height probably causes continuous overspill, testified by sediment waves migrating parallel to the channel. The scours occur in the intermediate part of the ridge where the ridge height is only 50-60 m; scours are interpreted as the result of cyclic steps due to flow stripping of currents provided by the intersection of the Khadra Canyon with the Kramis Canyon and Channel system. The scours probably postdate the main growth of the Kramis Ridge and induce the local erosion of the ridge, which could correspond to a new channel initiation cutting the ridge. The superposition or the interaction of flows with different directions is responsible of the amplification of the size of the sediment waves with erosional downside flanks and their transformation in scours. The Kramis Fan provides a clear example of flow interaction to explain the presence of large sediment waves and scours on modern submarine fans.

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