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9 results on '"Claire Croguennec"'

1. Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

Author

Livio Ruffine, Jean-Pierre Donval, Claire Croguennec, Laurent Bignon, Dominique Birot, Anne Battani, Germain Bayon, Jean-Claude Caprais, Nadine Lantéri, Denis Levaché, and Stéphanie Dupré

Subjects
Geology, QE1-996.5
Abstract

During the scientific expedition GAZCOGNE2 at the Bay of Biscay nine gas seeps were sampled for the first time and their flux was measured using an in situ pressure-preservation sampler (PEGAZ, ©IFREMER). Overall, three sites were investigated to determine the nature and the origin of the gases bubbling at the seafloor and forming acoustic plumes into the water column, as this was the question raised from the first geologic study of the area. This has guided our study and accordingly corresponds to the main purpose of the present article. Thus, the molecular and isotopic (δD and δ13C) analyses revealed that the gas seeps were primarily composed of methane. Both methane and ethane are of microbial origin, and the former has been generated by microbial reduction of carbon dioxide. Heavier hydrocarbons accounted for less than 0.06% mol of the total amount. Despite the microbial origin of methane, the samples exhibit subtle differences with respect to the δ13CCH4 values, which varied between −72.7 and −66.1‰. It has been suggested that such a discrepancy was predominantly governed by the occurrence of anaerobic methane oxidation. The PEGAZ sampler also enabled us to estimate the local gas fluxes from the sampled streams. The resulting values are extremely heterogeneous between seeps, ranging from 35 to 368 mLn·min−1. Assuming a steady discharge, the mean calculated methane emission for the nine seeps is of 38 kmol·yr−1. Considering the extent of the seep area, this very local estimate suggests that the Aquitaine Shelf is a very appropriate place to study methane discharge and its fate on continental shelves.

Published
2017
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2. A GC-SSIM-CRDS System: Coupling a Gas Chromatograph with a Cavity Ring-Down Spectrometer for Onboard Twofold Analysis of Molecular and Isotopic Compositions of Natural Gases during Ocean-Going Research Expeditions

Author

Jean-Claude Caprais, Vivien Guyader, Jean-Pierre Donval, Nolwenn LeCuff, Christophe Brandily, Alexis de Prunelé, Cecile Cathalot, Livio Ruffine, and Claire Croguennec

Subjects
Chromatography, Gas, Analytical chemistry, Natural Gas, Natural gases, Biochemistry, Methane, Analytical Chemistry, Cavity ring-down spectroscopy, Carbon cycle, chemistry.chemical_compound, Natural gas, Environmental Chemistry, Spectroscopy, Packed bed, Stable carbon isotope ratio, Carbon Isotopes, Gas chromatography, business.industry, Spectrum Analysis, Coupled analytical technique, chemistry, Carbon dioxide, Onboard analysis, Isotopes of carbon, Molecular composition, Expeditions, Gases, business
Abstract

Carbon dioxide (CO2) and methane (CH4) are two climate-sensitive components of gases migrating within sediments and emitted into the water column on continental margins. They are involved in several key biogeochemical processes entering into the global carbon cycle. In order to perform onboard measurements of both the molecular and stable carbon isotope ratios (δ13C) of CH4 and CO2 of natural gases during oceanic cruises, we have developed a novel approach coupling gas chromatography (GC) with cavity ring-down spectroscopy (CRDS). The coupled devices are connected to a small sample isotope module (SSIM) to form a system called GC-SSIM-CRDS. Small volumes of natural gas samples (

Published
2021

3. Focused hydrocarbon-migration in shallow sediments of a pockmark cluster in the Niger Delta (Off Nigeria)

Author

Claire Croguennec, Marc Lescanne, Abdulkarim Rabiu, Vivien Guyader, Germain Bayon, Thomas Pape, Gerhard Bohrmann, Nabil Sultan, Vincent Riboulot, E. Cauquil, Yoan Germain, Jean Pierre Donval, Claire Bollinger, Jean Claude Caprais, Alexis de Prunelé, Louis Géli, Livio Ruffine, Carl A. Peters, and Tania Marsset

Subjects
010504 meteorology & atmospheric sciences, Pockmark, Clathrate hydrate, Geochemistry, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Seafloor spreading, chemistry.chemical_compound, Geophysics, Oceanography, chemistry, 13. Climate action, Geochemistry and Petrology, Transition zone, Anaerobic oxidation of methane, Carbonate, Submarine pipeline, Sedimentary rock, 14. Life underwater, Geology, 0105 earth and related environmental sciences
Abstract

The Niger Delta is one of the largest hydrocarbon basin offshore Africa and it is well known for the presence of active pockmarks on the seabed. During the Guineco-MeBo cruise in 2011, long cores were taken from a pockmark cluster in order to investigate the state of its current activity. Gas hydrates, oil and pore-water were sampled for geochemical studies. The resulting dataset combined with seismic data reveal that shallow hydrocarbon migration in the upper sedimentary section was focused exclusively within the pockmarks. There is a clear tendency for gas migration within the hydrate-bearing pockmarks, and oil migration within the carbonate-rich one. This trend is interpreted as a consequence of hydrate dissolution followed by carbonate precipitation in the course of the evolution of these pockmarks. We also demonstrate that Anaerobic Oxidation of Methane (AOM) is the main process responsible for the depletion of pore-water sulfate, with depths of the Sulfate-Methane Transition Zone (SMTZ) ranging between 1.8 and 33.4 m. In addition, a numerical transport-reaction model was used to estimate the age of hydrate-layer formation from the present-day sulfate profiles. The results show that the sampled hydrate-layers were formed between 21 and 3750 years before present. Overall, this work shows the importance of fluid flow on the dynamics of pockmarks, and the investigated cluster offers new opportunities for future cross-site comparison studies. Our results imply that sudden discharges of gas can create hydrate layers within the upper sedimentary column which can affect the seafloor morphology over few decades. This article is protected by copyright. All rights reserved.

Published
2017
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4. Multiple gas reservoirs are responsible for the gas emissions along the Marmara fault network

Author

M. Namık Çağatay, Yoan Germain, Pete Burnard, Mathilde Pitel-Roudaut, Jean-Pierre Donval, Pierre Henry, Laurent Bignon, Claire Croguennec, David Madre, Bernard Marty, Louis Géli, Livio Ruffine, Ludovic Nicolas Legoix, Hailong Lu, Unité de recherche Géosciences Marines (Ifremer) (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Peking University [Beijing], Istanbul Technical University, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Laboratoire Interdisciplinaire de Recherche Impliquant la Géologie et la Mécanique (LIRIGM), Université Joseph Fourier - Grenoble 1 (UJF), Université de Lorraine (UL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Géosciences Marines (GM), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and 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)

Subjects
Sea of Marmara, 010504 meteorology & atmospheric sciences, Methanogenesis, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Structural basin, 010502 geochemistry & geophysics, Oceanography, Molecular and isotopic compositions, 01 natural sciences, Methane, chemistry.chemical_compound, Water column, Continental margin, 0105 earth and related environmental sciences, Abiotic CO2-source, Seeps, Primary and secondary methanogenesis, 15. Life on land, 6. Clean water, Cold seep, Gas bubbles, Petroleum seep, chemistry, [SDU]Sciences of the Universe [physics], 13. Climate action, Thermogenic gases, Environmental science, Sedimentary rock
Abstract

International audience; On continental margins, upward migration of fluids from various sources and various subsurface accumulations, through the sedimentary column to the seafloor, leads to the development of cold seeps where chemical compounds are discharged into the water column. MarsiteCruise was undertaken in November 2014 to investigate the dynamics of cold seeps characterized by vigorous gas emissions in the Sea of Marmara (SoM).A previous paper published by Bourry et al. (2009) presented the gas geochemistry of three seeps sampled along three different segments in the SoM. Their findings showed that the seeps were sourced by three different reservoirs. In this paper, seventeen seeps were investigated to determine the gas sources, unravel reservoir contributions, and estimate their level of mixing. The molecular and stable isotope compositions of the gas compounds were determined to establish the empirical diagrams that usually allow to delineate source domains. The results provide insights into the complexities of source mixing within the sedimentary column of the SoM before emission of the gases into the water column. The seep gases originate from deep thermogenic or microbial hydrocarbon sources, or from a CO2-rich source. Microbial sources producing methane from primary methanogenesis have been identified in the Tekirdağ and the Çınarcık basins. In addition, six different thermogenic reservoirs or six different pathways of migration are responsible for the supply of gas to the seeps on the highs and in the western basin. Five of them are undergoing biodegradation followed by secondary methanogenesis, thereby providing additional sources of microbial methane to the seeps. Overall, the gases emitted by the seventeen seeps consist of variable mixtures of different components from two or three sources.

Published
2018
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5. Pore water geochemistry at two seismogenic areas in the Sea of Marmara

Author

Louis Géli, Livio Ruffine, Jean-Pierre Donval, Christophe Brandily, Claire Bollinger, Alexis de Prunelé, Claire Croguennec, Alina Polonia, Emmanuel Ponzevera, Luca Gasperini, Mathilde Pitel-Roudaut, Yoan Germain, Céline Grall, and Jean-Claude Caprais

Subjects
Strontium, Recrystallization (geology), 010504 meteorology & atmospheric sciences, Geochemistry, North Anatolian Fault, chemistry.chemical_element, 010502 geochemistry & geophysics, 01 natural sciences, chemistry.chemical_compound, Geophysics, Mediterranean sea, chemistry, 13. Climate action, Geochemistry and Petrology, Anaerobic oxidation of methane, Carbonate, Seawater, 14. Life underwater, Sulfate, Geology, 0105 earth and related environmental sciences
Abstract

Within the Sea of Marmara, the highly active North Anatolian Fault (NAF) is responsible for major earthquakes (Mw 7), and acts as a pathway for fluid migration from deep sources to the seafloor. This work reports on pore water geochemistry from three sediment cores collected in the Gulfs of Izmit and Gemlik, along the Northern and the Middle strands of the NAF, respectively. The resulting data set shows that anaerobic oxidation of methane (AOM) is the major process responsible for sulfate depletion in the shallow sediment. In the Gulf of Gemlik, depth concentration profiles of both sulfate and alkalinity exhibit a kink-type profile. The Sulfate Methane Transition Zone (SMTZ) is located at moderate depth in the area. In the Gulf of Izmit, the low concentrations observed near the seawater-sediment interface for sulfate, calcium, strontium, and magnesium result from rapid geochemical processes, AOM, and carbonate precipitation, occurring in the uppermost part of the sedimentary column and sustained by free methane accumulation. Barite dissolution and carbonate recrystallization have also been identified at deeper depth at the easternmost basin of the Gulf of Izmit. This is supported by the profile of the strontium isotope ratios (87 Sr/ 86 Sr) as a function of depth which exhibits negative anomalies compared to the modern seawater value. The strontium isotopic signature also shows that these carbonates had precipitated during the reconnection of the Sea of Marmara with the Mediterranean Sea. Finally, a first attempt to interpret the sulfate profiles observed in the light of the seismic activity at both sites is presented. We propose the hypothesis that seismic activity in the areas is responsible for the transient sulfate profile, and that the very shallow SMTZ depths observed in the Gulf of Izmit is likely due to episodic release of significant amount of methane.

Published
2015
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6. Multidisciplinary investigation on cold seeps with vigorous gas emissions in the Sea of Marmara (MarsiteCruise): Strategy for site detection and sampling and first scientific outcome

Author

Claire Croguennec, Joel Etoubleau, Lucas Gasperini, Jean-Pierre Donval, Harald Strauss, Christian Podeur, Laurent Bignon, Christophe Fontanier, Ludovic Nicolas Legoix, Volkan Özaksoy, Emmanuel Rinnert, Davide Embriaco, Marie-Madeleine Blanc-Valleron, Jonathan Perchoc, Catherine Pierre, Carla Scalabrin, Pete Burnard, Delphine Dissard, Stéphanie Dupré, Bastien Thomas, Mathilde Pitel-Roudaut, M. Namık Çağatay, David Madre, Hélène Ondréas, Dominique Birot, Barbara M.A. Teichert, Eyyüp Özbeki, Yoan Germain, Céline Grall, Françoise Lesongeur, Emmanuel Ponzevera, Jean-Claude Caprais, Alina Polonia, Corinne Tarditi, Vivien Guyader, Pierre Henry, Hailong Lu, A.S. Alix, Louis Géli, Livio Ruffine, Hailin Yang, Nazli Olgun, Bernard Marty, Angélique Roubi, Joël Knoery, Nicolas Chevalier, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Westfälische Wilhelms-Universität Münster = University of Münster (WWU), Cycles biogéochimiques marins : processus et perturbations (CYBIOM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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)-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)), 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 de Lorraine (UL), Peking University [Beijing], Variabilité à long terme du climat de l'océan (VALCO), Istanbul Technical University (ITÜ), General Directorate of Mineral Research and Exploration, The Mineral Etude and Research Department, Ankara, Turkey 06520, Géosciences Marines (GM), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géosciences et Environnement Cergy (GEC), Fédération INSTITUT DES MATÉRIAUX DE CERGY-PONTOISE (I-MAT), Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine, Lamont-Doherty Earth Observatory (LDEO), Columbia University [New York], Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Roma (INGV), Istituto Nazionale di Geofisica e Vulcanologia, Istituto di Scienze Marine [Bologna] (ISMAR), Istituto di Science Marine (ISMAR ), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR)-National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), 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), Laboratoire Interdisciplinaire de Recherche Impliquant la Géologie et la Mécanique (LIRIGM), Université Joseph Fourier - Grenoble 1 (UJF), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), European Project: 308417,EC:FP7:ENV,FP7-ENV-2012-two-stage,MARSITE(2012), Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), Westfälische Wilhelms-Universität Münster (WWU), 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)-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), Istanbul Technical University, Unité de recherche Géosciences Marines (Ifremer) (GM), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Consiglio Nazionale delle Ricerche (CNR)-Consiglio Nazionale delle Ricerche (CNR), 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), ANR: 10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC), 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)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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), and 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)

Subjects
Dissolved major elements, 010504 meteorology & atmospheric sciences, North Anatolian Fault, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Context (language use), 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Acoustic survey, Fluid seepage, Water column, 14. Life underwater, Chemical analyses, 0105 earth and related environmental sciences, Sediment, Geology, Authigenic, Biogeochemistry, In situ Raman analysis, Cold seep, Cold seeps, ROV dives, Authigenic carbonates, Methane, Petroleum seep, 13. Climate action, [SDU]Sciences of the Universe [physics], Environmental science, Seawater
Abstract

International audience; MarsiteCruise was undertaken in October/November 2014 in the Sea of Marmara to gain detailed insight into the fate of fluids migrating within the sedimentary column and partially released into the water column. The overall objective of the project was to achieve a more global understanding of cold-seep dynamics in the context of a major active strike-slip fault. Five remotely operated vehicle (ROV) dives were performed at selected areas along the North Anatolian Fault and inherited faults.To efficiently detect, select and sample the gas seeps, we applied an original procedure. It combines sequentially (1) the acquisition of ship-borne multibeam acoustic data from the water column prior to each dive to detect gas emission sites and to design the tracks of the ROV dives, (2) in situ and real-time Raman spectroscopy analysis of the gas stream, and (3) onboard determination of molecular and isotopic compositions of the collected gas bubbles. The in situ Raman spectroscopy was used as a decision-making tool to evaluate the need for continuing with the sampling of gases from the discovered seep, or to move to another one. Push cores were gathered to study buried carbonates and pore waters at the surficial sediment, while CTD-Rosette allowed collecting samples to measure dissolved-methane concentration within the water column followed by a comparison with measurements from samples collected with the submersible Nautile during the Marnaut cruise in 2007.Overall, the visited sites were characterized by a wide diversity of seeps. CO2- and oil-rich seeps were found at the westernmost part of the sea in the Tekirdag Basin, while amphipods, anemones and coral populated the sites visited at the easternmost part in the Cinarcik Basin. Methane-derived authigenic carbonates and bacterial mats were widespread on the seafloor at all sites with variable size and distributions. The measured methane concentrations in the water column were up to 377 μmol, and the dissolved pore-water profiles indicated the occurrence of sulfate depleting processes accompanied with carbonate precipitation. The pore-water profiles display evidence of biogeochemical transformations leading to the fast depletion of seawater sulfate within the first 25-cm depth of the sediment. These results show that the North Anatolian Fault and inherited faults are important migration paths for fluids for which a significant part is discharged into the water column, contributing to the increase of methane concentration at the bottom seawater and favoring the development of specific ecosystems.

Published
2018
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7. Corrigendum to 'Multiple gas reservoirs are responsible for the gas emissions along the Marmara fault network'

Author

Claire Croguennec, Pete Burnard, Mathilde Pitel-Roudaut, David Madre, Jean-Pierre Donval, Bernard Marty, Louis Géli, Laurent Bignon, Ludovic Nicolas Legoix, Livio Ruffine, Pierre Henry, Yoan Germain, M. Namık Çağatay, Hailong Lu, Laboratoire Géosciences Océan (LGO), 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 Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), College of Engineering [Beijing], Peking University [Beijing], Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Maden Fakültesi = Faculty of mines [Istanbul], Istanbul Technical University (ITÜ), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), and Institut de Recherche pour le Développement (IRD)-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)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
0106 biological sciences, Oceanography, 010504 meteorology & atmospheric sciences, [SDU]Sciences of the Universe [physics], 010604 marine biology & hydrobiology, Gas emissions, Petrology, Fault (power engineering), 01 natural sciences, Geology, 0105 earth and related environmental sciences
Abstract

International audience; The authors regret a mistake on the value of δ13C of methane for one of the investigated gas samples. This concerns sample MRS-DV3-PE03, taken as end member and for which the correct methane δ13C value is -41.9‰ and not -34‰. The sample was collected at in situ pressure ( 100 bars) from a CO2-rich seep, in a liquid state. The mistake likely results from a partial extraction (i.e. done by expansion of the sampler volume to allow vaporization) of the pressurized sample for subsampling. Additional analyses have been carried out from fully vaporized samples. This error has resulted in updating the geochemical diagrams used for the discussion, and revising both the gas origin for sample MRS-DV3-PE03 and the section entitled "Delineation of sources, reservoirs or migration pathways, and estimation of level of mixing". The conclusion of the manuscript is unchanged. The authors would like to apologize for any inconvenience caused.

Published
2018
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8. 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
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9. 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
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