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1. A honeycomb seafloor morphology in carbonate sediment of the Carnegie Ridge (offshore Ecuador): Formation and potential geodynamic significance

Author

L. de Min, Hugo Pouderoux, G. Loayza, Jean-Noël Proust, A. Khaoulani, Jean-Frederic Lebrun, François Michaud, Alexandre Dano, M.J. Hernández, Y. Stoll, Jean-Yves Collot, Gueorgui Ratzov, 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 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), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Université des Antilles (UA), Escuela Superior Politécnica del Litoral (ESPOL), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), and 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])

Subjects
010504 meteorology & atmospheric sciences, Subduction, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Drilling, Geology, 010502 geochemistry & geophysics, 01 natural sciences, Deep sea, Seafloor spreading, chemistry.chemical_compound, Basement (geology), chemistry, Ridge (meteorology), Carbonate, Bathymetry, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 14. Life underwater, 0105 earth and related environmental sciences
Abstract

International audience; Based on swath bathymetry, two-dimensional, high-resolution seismic reflection profiles, and Ocean Drilling Program/Deep Sea Drilling Project (ODP/DSDP) data, we describe a seafloor honeycomb pattern and propose a model for its formation in Pliocene–Miocene carbonate deposited on the uneven oceanic basement of the Carnegie Ridge (offshore Ecuador). Hydrothermal fluids derived from the basement aquifer fractured and dissolved carbonate sediment, creating seafloor pits above basements highs. Fluids expelled along polygonal faults may have assisted the nucleation of seafloor depressions. At the Pliocene-Pleistocene boundary, strong bottom currents scoured previously damaged sediments, enlarging the initial depressions and producing the seafloor honeycomb pattern. This regional erosive episode was contemporaneous with the final closing of the Isthmus of Panama and the clogging of the Ecuador Trench by the subduction of the Carnegie Ridge, so that the honeycomb pattern may be viewed as a regional marker of these two geodynamic events.

Published
2018
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2. Frequency and triggering of small-scale submarine landslides on decadal timescales: Analysis of 4D bathymetric data from the continental slope offshore Nice (France)

Author

Alfredo Taboada, Sébastien Migeon, Emmanuel Tric, Alexandre Dano, Françoise Couboulex, Maëlle Kelner, Thomas Lebourg, Géoazur (GEOAZUR 7329), 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)-Université Côte d'Azur (UCA), 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 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, 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
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Continental shelf, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Sediment, Geology, Landslide, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Deposition (geology), 13. Climate action, Geochemistry and Petrology, Erosion, Bathymetry, Submarine pipeline, 14. Life underwater, Geomorphology, 0105 earth and related environmental sciences, Submarine landslide
Abstract

International audience; Time-series bathymetric data acquired from 1967 to 2011 are used to evaluate the morphological evolution of the continental shelf and upper continental slope off the city of Nice (SE France, Ligurian Sea). Mapping in water depths of 0–300 m was undertaken to identify the changing morphology of landslide scars and their erosive chutes. Quantitative Digital Terrain Model (DTM) comparisons reveal areas of erosion and deposition over intervals of 5–8 years. Sediment remobilization events on the upper slope (above depths of 200 m) are frequent and significant; landslide scars with volumes > 25,000 m3 can occur with frequencies of < 8 years. Shelf break retreat toward the coastline can reach 60 m over 7–8 years where the continental shelf is wider (> 200 m). Periods of quiescence (1980–1990 and 2006–2011) are seen to alternate with periods when rapid retrogressive failure increase sediment volumes eroded from the upper slope-shelf transition by an order of magnitude (1999–2006). Temporal variations in landslide activity were correlated to several potential triggering factors that individually would not induce failures, including earthquake activity, rapid deposition of fine-grained sediments on a steep slope, and rainfall leading to fresh groundwater circulation below the shelf. This 4D bathymetric study suggests that over the last 50 years the most important factor triggering landslides offshore Nice is overpressure due to freshwater outflows.

Published
2016
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4. Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian Margin: Relationship with Active Tectonics and Gas Hydrates

Author

Hugo Pouderoux, Jean-Yves Collot, Maria José Hernandez Salazar, Carlos Martillo, Alexandre Dano, Laure Schenini, Grâce Daniella Guiyeligou, Jean-Frederic Lebrun, Glenda Loayza, François Michaud, Jean-Noël Proust, Gueorgui Ratzov, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 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, 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), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Service de la Géologie de Nouvelle Calédonie, Direction de l'Industrie, des Mines et de l'Energie de Nouvelle Calédonie, 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), 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)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), 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 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, Acoustics, Multibeam, Clathrate hydrate, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Continental margin, Active fault, Subduction, 010502 geochemistry & geophysics, 01 natural sciences, Seepage, Seafloor spreading, Backscatter, Tectonics, Geophysics, Echo sounding, Water column, Geochemistry and Petrology, Ecuador, Fluid, Forearc, Geology, Seismology, 0105 earth and related environmental sciences
Abstract

International audience; With hull-mounted multibeam echosounder data, wereport for the first time along the active Ecuadorian margin,acoustic signatures of water column fluid emissions and seep-relatedstructures on the seafloor. In total 17 flare-shaped acousticanomalies were detected from the upper slope (1250 m) to the shelfbreak (140 m). Nearly half of the flare-shaped acoustic anomaliesrise 200–500 m above the seafloor. The base of the flares is generallyassociated with high-reflectivity backscatter patchescontrasting with the neighboring seafloor. We interpret these flaresas caused by fluid escape in the water column, most likely gases.High-resolution seismic profiles show that most flares occur closeto the surface expression of active faults, deformed areas, slopeinstabilities or diapiric structures. In two areas tectonic deformationdisrupts a Bottom Simulating Reflector (BSR), suggesting thatburied frozen gas hydrates are destabilized, thus supplying free gasemissions and related flares. This discovery is important as it opensthe way to determine the nature and origin of the emitted fluids andtheir potential link with the hydrocarbon system of the forearcbasins along the Ecuadorian margin.

Published
2016
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5. Quaternary sedimentation and active faulting along the Ecuadorian shelf: preliminary results of the ATACAMES Cruise (2012)

Author

Alexandre Dano, M. J. Hernández, François Michaud, César Witt, M. Calderon, L. de Min, G. Loayza, Gueorgui Ratzov, L. Penafiel, L. Schenini, Jean-Frédéric Lebrun, D. Barba, G. Ponce, Carlos Martillo, M. Gonzalez, Hugo Pouderoux, A. Urresta, Jean-Noël Proust, Jean-Yves Collot, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 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, 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), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), 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)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), 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 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
Canyon, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Subduction, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Subsidence, 15. Life on land, Fault (geology), 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Tectonics, Geophysics, Continental margin, 13. Climate action, Geochemistry and Petrology, Sedimentary rock, 14. Life underwater, Sediment transport, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

International audience; Selected high-resolution seismic-reflection profiles and multibeam bathymetry acquired along the convergent Ecuador margin during the ATACAMES cruise on onboard the R/V L’Atalante (Jan.15–Feb.18, 2012) allow a preliminary evaluation of the neotectonic development and stratigraphic evolution of the margin based on the sismo-stratigraphic analysis of Quaternary sediment preserved on the margin shelf and upper slope. We present three major preliminary results. (1) The evolution of the Esmeraldas, Guayaquil and Santa Elena canyons. The head of the Esmeraldas canyon is the location of a continuous significant sediment transport. The Guayaquil canyon shows several episodes of deposition and incision. Aggrading sedimentation pattern in the canyon records several changes in relative sea-level. The subsidence of the Gulf of Guayaquil probably contributes to the good preservation of the canyon filling stages. The Santa Elena canyon is controlled by a SW–NE trending normal fault. (2) Variations of sediment accumulation and relative vertical motions are shown along-strike the shelf edge. Offshore the uplifted Manta peninsula, a pronounced subsidence of the shelf edge is documented by sedimentary clinoforms that have deposited in a morphological reentrant, and have migrated upslope testifying of a local subsidence meanwhile the adjacent La Plata Island area underwent uplift. In the Esmeraldas canyon area, a local uplift of the shelf is documented. (3) Two neotectonic fault systems with a possible transcurrent component are imaged across the shelf edge and upper margin slope offshore Jama, and Cape Galera. This possible transcurrent motion could be related to the reactivation of ancient faults of the upper plate by the subduction. These preliminary results indicate that the ATACAMES data set has a strong potential to evaluate the spatial and temporal contribution of tectonic and climate changes on the structural development and stratigraphic evolution of the Ecuador continental margin.

Published
2015
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6. Recent Morphological Changes of the Nice Continental Slope

Author

Françoise Couboulex, Maëlle Kelner, Thomas Lebourg, Sébastien Migeon, Emmanuel Tric, Alexandre Dano, Alfredo Taboada, Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-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)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 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, 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), Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), 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]), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), 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
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Continental shelf, Lead (sea ice), Sediment, Landslide, Geomorphology, Sedimentation, 010502 geochemistry & geophysics, Fault scarp, 01 natural sciences, Fresh water, 13. Climate action, Bathymetry, 14. Life underwater, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Ligurian sea Geohazards, Geology, 0105 earth and related environmental sciences, Continental slope
Abstract

Time-series bathymetric data acquired between 1991 and 2011 have been used to evaluate the recent morphological evolution of the Nice upper continental slope (SE France, Ligurian Sea). Small-scale landslides lead to a retrogressive evolution of the continental shelf/upper slope transition but their frequency, size and impact are not well known. Mapping was undertaken to identify the morphology of landslide scarps and the location of the shelfbreak. Map comparisons were performed using ArcGIS “raster calculator”. Sediment remobilization on the upper slope (up to depths of 200 m) is fast and significant; landslide scars with volumes greater than 25,000 m3 can appear with a frequency less than 8 years. Shelfbreak migration toward the coastline can reach rates of 60 m over 7–8 years where the continental shelf is over 200 m wide. Furthermore, this quantitative analysis highlights alternations between periods of strongly erosive events and sedimentation periods. On the upper slope, eroded volumes can be multiplied by 10 during periods of enhanced landslide patterns (1999–2006). Such cycle-like landslide activity raises the issue of the triggering processes. On the Nice continental slope thick poorly consolidated beds rapidly deposited on a steep slope, earthquakes and rainfall leading to fresh water circulation below the shelf were identified as potential triggers. Our 4D bathymetric study suggests that over the last 20 years the greatest impacting factor may be freshwater outflows.

Published
2014
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7. Fluid Seepage in Relation to Seabed Deformation on the Central Nile Deep-Sea Fan, Part 1: Evidence from Sidescan Sonar Data

Author

Emmanuelle Ducassou, Sébastien Migeon, Jean-Marie Augustin, Adolpho Herbert Augustin, Jean Mascle, João Marcelo Ketzer, Alexandre Dano, Daniel Praeg, Silvia Ceramicola, Géoazur (GEOAZUR 7329), 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]), Istituto Nazionale di Geofisica e di Oceanografia Sperimentale (OGS), Institut français de recherche pour l'exploitation de la mer (IFREMER), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), CEPAC, Environnements et Paléoenvironnements OCéaniques (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)-Centre National de la Recherche Scientifique (CNRS), 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), 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), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Sediment deformation, 010504 meteorology & atmospheric sciences, Sediment, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Authigenic, 010502 geochemistry & geophysics, 01 natural sciences, Sonar, Deep sea, Fluid seepage, Backscatter, chemistry.chemical_compound, Gas flares, chemistry, Fluid dynamics, Carbonate, 14. Life underwater, Transect, Geomorphology, Seismology, Seabed, Geology, 0105 earth and related environmental sciences
Abstract

International audience; The central Nile Deep-Sea Fan contains a broad area of seabed destabilisation in association with fluid seepage: slope-parallel sediment undulations are associated with multibeam high-backscatter patches (HBPs) related to authigenic carbonates. During the 2011 APINIL campaign, a deep-towed sidescan and profiling system (SAR) was used to acquire high-resolution data along three transects across water depths of 1,700-2,650 m. Three seabed domains are distinguished, all developed within stratified sediments overlying mass-transport deposits (MTDs). Upslope of the undulations (

Published
2014
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8. Fluid Seepage in Relation to Seabed Deformation on the Central Nile Deep-Sea Fan, Part 2: Evidence from Multibeam and Sidescan Imagery

Author

Adolpho Herbert Augustin, Luiz F. Rodrigues, Sébastien Migeon, Jean Mascle, Stéphanie Dupré, João Marcelo Ketzer, Alexandre Dano, Emmanuelle Ducassou, Silvia Ceramicola, Daniel Praeg, Istituto Nazionale di Geofisica e di Oceanografia Sperimentale (OGS), CEPAC, 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), Environnements et Paléoenvironnements OCéaniques (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), IFREMER, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 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]), and 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)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Faults, 010504 meteorology & atmospheric sciences, Carbonates, Sediment, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Deep sea, Backscatter, chemistry.chemical_compound, Slope undulations, chemistry, Carbonate, Evolving systems, Pipes, 14. Life underwater, Fluid seeps, Geomorphology, Geology, Seabed, 0105 earth and related environmental sciences
Abstract

International audience; On the central Nile deep-sea fan, stratified sediments overlying mass-transport deposits (MTDs) are deformed into slope-parallel seabed undulations associated with fluid seepage. The western part of this system, in water depths of 1,950-2,250 m, is examined using multi-frequency data from hull-mounted and deep-towed swath/profiling systems. Sub-bottom profiles show sub-vertical fluid pipes that terminate both at and below seabed, and gas signatures along fault planes bounding the undulations. Fluid seepage is recorded by high- to intermediate-backscatter patches (HBPs, IBPs) that differ in appearance on multibeam imagery (30 kHz, ≤3 m penetration) and sidescan swaths (170/190 kHz

Published
2014
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9. Post-failure Processes on the Continental Slope of the Central Nile Deep-Sea Fan: Interactions Between Fluid Seepage, Sediment Deformation and Sediment-Wave Construction

Author

Silvia Ceramicola, Daniel Praeg, Jean Mascle, Sébastien Migeon, João Marcelo Ketzer, Flore Mary, Emmanuelle Ducassou, and Alexandre Dano

Subjects
geography, Gravity (chemistry), geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Deformation (mechanics), Continental shelf, Sediment, 010502 geochemistry & geophysics, 01 natural sciences, Deep sea, Seafloor spreading, chemistry.chemical_compound, chemistry, Carbonate, Geomorphology, Geology, Seabed, 0105 earth and related environmental sciences
Abstract

Voluminous mass-transport deposits (MTD) have been identified on seismic profiles across the central Nile Deep-Sea Fan (NDSF). The youngest MTDs are buried under 30–100 m of well-stratified slope deposits that, in water depths of 1,800–2,600 m, are characterized by undulating reflectors correlated with slope-parallel seabed ridges and troughs. Seabed imagery shows that, in the western part of the central NDSF, short, arcuate undulations are associated with fluid venting (carbonate pavements, gas flares), while to the east, long, linear undulations have erosional furrows on their downslope flanks and fluid seeps are less common. Sub-bottom profiles suggest that the western undulations correspond to rotated fault-blocks above the buried MTDs, while those in the east are sediment waves generated by gravity flows. We suggest that fluids coming from dewatering of MTDs and/or from deeper layers generate overpressures along the boundary between MTDs and overlying fine-grained sediment, resulting in a slow downslope movement of the sediment cover and formation of tilted blocks separated by faults. Fluids can migrate to the seafloor, leading to the construction of carbonate pavements. Where the sediment cover stabilizes, sediment deposition by gravity flows may continue building sediment waves. These results suggest that complex processes may follow the emplacement of large MTDs, significantly impacting continental-slope evolution.

Published
2013
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11. Failure processes and gravity-flow transformation revealed by high-resolution AUV swath bathymetry on the Nice continental slope (Ligurian Sea)

Author

Etienne Ruellan, Antonio Cattaneo, Aurélie Casedevant, V. Hassoun, Sébastien Migeon, Alexandre Dano, 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), 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), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), 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), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), 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), Laboratoire Environnements Sédimentaires - Géosciences Marines (GM/LES), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 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), and Géoazur, Publications

Subjects
geography, geography.geographical_feature_category, Bedform, 010504 meteorology & atmospheric sciences, Continental shelf, Turbulence, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, Geodesy, 01 natural sciences, Wavelength, Erosion, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, Submarine pipeline, Bathymetry, 14. Life underwater, Geomorphology, Geology, 0105 earth and related environmental sciences, Submarine landslide
Abstract

International audience; The continental slope offshore Nice is a natural laboratory to investigate submarine landslides and gravity-flow processes. Using EM300 bathymetry data (spatial resolution of 25 m), about 250 scars with volume less than 8 × 108 m3 were identified. The AUV bathymetric data (spatial resolution of 2 m) revealed a greater number of scar-related failures with two main morphologies: some scars are affected by retrogressive processes of erosion, suggesting failures were triggered a long time ago, while other scars exhibit no evidence of post-failure erosion, suggesting they could have been triggered recently. Downslope from the scars, there are scattered blocks, on average 5-m high and 40-m wide, and well-developed asymmetrical waves, on average 2-m high and 20-m in wavelength. Such evolution could be evidence for the transformation of the remobilized deposits into cohesive flows then turbulent flows. Such transformation took place over a distance of less than 6-8 km.

Published
2011

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