193 results on '"Bourillet, Jean-francois"'
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2. The 'Turritella Layer': A Potential Proxy of a Drastic Holocene Environmental Change on the North–East Atlantic Coast
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Baltzer, Agnès, Mokeddem, Zohra, Goubert, Evelyne, Lartaud, Franck, Labourdette, Nathalie, Fournier, Jérôme, Bourillet, Jean-François, Finkl, Charles W., Series editor, Maanan, Mohamed, editor, and Robin, Marc, editor
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- 2015
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3. Millennial-scale fluctuations of the European Ice Sheet at the end of the last glacial, and their potential impact on global climate
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Toucanne, Samuel, Soulet, Guillaume, Freslon, Nicolas, Silva Jacinto, Ricardo, Dennielou, Bernard, Zaragosi, Sébastien, Eynaud, Frédérique, Bourillet, Jean-François, and Bayon, Germain
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- 2015
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4. Integrating Prior Knowledge and Locally Varying Parameters with Moving-GeoStatistics: Methodology and Application to Bathymetric Mapping
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Magneron, Cedric, Jeannee, Nicolas, Le Moine, Olivier, Bourillet, Jean-François, Atkinson, P. M., editor, and Lloyd, C. D., editor
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- 2010
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5. External controls on turbidite sedimentation on the glacially-influenced Armorican margin (Bay of Biscay, western European margin)
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Toucanne, Samuel, Zaragosi, Sebastien, Bourillet, Jean-François, Dennielou, Bernard, Jorry, Stephan J., Jouet, Gwenael, and Cremer, Michel
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- 2012
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6. MACROCOSME, An Innovative Buoy To Assess Marine Environment Ecological Health
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Legrand Julien, Perie Frederic, Bourillet Jean-Francois, Barbero Aurore, Bouchoucha Marc, and Lagadec Jean-Romain
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- 2021
7. Buried fluvial incisions as a record of Middle–Late Miocene eustasy fall on the Armorican Shelf (Bay of Biscay, France)
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Paquet, Fabien, Menier, David, Estournès, Guilhem, Bourillet, Jean-François, Leroy, Pascal, and Guillocheau, François
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- 2010
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8. The North Atlantic Glacial Eastern Boundary Current as a key driver for ice‐sheet – AMOC interactions and climate instability
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Toucanne, Samuel, Soulet, Guillaume, Vazquez Riveiros, Natalia, Boswell, Steven M., Dennielou, Bernard, Waelbroeck, Claire, Bayon, Germain, Mojtahid, Meryem, Bosq, Mathieu, Sabine, Marjolaine, Zaragosi, Sébastien, Bourillet, Jean-francois, Mercier, Herle, Toucanne, Samuel, Soulet, Guillaume, Vazquez Riveiros, Natalia, Boswell, Steven M., Dennielou, Bernard, Waelbroeck, Claire, Bayon, Germain, Mojtahid, Meryem, Bosq, Mathieu, Sabine, Marjolaine, Zaragosi, Sébastien, Bourillet, Jean-francois, and Mercier, Herle
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The upper branch of the Atlantic Meridional Overturning Circulation (AMOC) plays a critical role in ocean circulation and climate change, yet its variability during the last glacial period is poorly documented. Here, we investigate the northward‐flowing Glacial Eastern Boundary Current (GEBC) in the North Atlantic, known today as the European Slope Current, and representing the easternmost portion of the upper branch of the AMOC. Based on flow speed and isotopic records, we show that Dansgaard‐Oeschger (D/O) interstadials (stadials) correspond to a faster (weaker) GEBC during the ∼50‐15 ka period. This, by analogy to present‐day conditions, suggests enhanced (reduced) strength of the subpolar gyre and, by extension, of northern‐sourced water production and AMOC during D‐O interstadials (stadials). Concomitant fluctuations of both the GEBC and the European Ice Sheet between ∼30 and 17 ka suggest an active role of the upper branch of AMOC in the poleward transport of heat and freshwater to the northern North Atlantic, with direct impacts on deep water formation and AMOC strength. We explore these ice‐sheet ‐ AMOC interactions and the associated abrupt climate changes over the last glacial period and the last deglaciation.
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- 2021
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9. Sedimentary sequences in the Gulf of Lion: A record of 100,000 years climatic cycles
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Rabineau, Marina, Berné, Serge, Aslanian, Daniel, Olivet, Jean-Louis, Joseph, Philippe, Guillocheau, François, Bourillet, Jean-François, Ledrezen, Eliane, and Granjeon, Didier
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- 2005
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10. Out of the Mediterranean? Post‐glacial colonization pathways varied among cold‐water coral species
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Boavida, Joana, Becheler, Ronan, Choquet, Marvin, Frank, Norbert, Taviani, Marco, Bourillet, Jean-francois, Meistertzheim, Anne‐leila, Grehan, Anthony, Savini, Alessandra, Arnaud-haond, Sophie, Boavida, Joana, Becheler, Ronan, Choquet, Marvin, Frank, Norbert, Taviani, Marco, Bourillet, Jean-francois, Meistertzheim, Anne‐leila, Grehan, Anthony, Savini, Alessandra, and Arnaud-haond, Sophie
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Aim To infer cold‐water corals’ (CWC) post‐glacial phylogeography and assess the role of Mediterranean Sea glacial refugia as origins for the recolonization of the northeastern Atlantic Ocean. Location Northeastern Atlantic Ocean and Mediterranean Sea. Taxon Lophelia pertusa, Madrepora oculata. Methods We sampled CWC using remotely operated vehicles and one sediment core for coral and sediment dating. We characterized spatial genetic patterns (microsatellites and a nuclear gene fragment) using networks, clustering and measures of genetic differentiation. Results Inferences from microsatellite and sequence data were congruent, and showed a contrast between the two CWC species. Populations of L. pertusa present a dominant pioneer haplotype, local haplotype radiations and a majority of endemic variation in lower latitudes. Madrepora oculata populations are differentiated across the northeastern Atlantic and genetic lineages are poorly admixed even among neighbouring sites. Conclusions Our study shows contrasting post‐glacial colonization pathways for two key habitat‐forming species in the deep sea. The CWC L. pertusa has likely undertaken a long‐range (post‐glacial) recolonization of the northeastern Atlantic directly from refugia located along southern Europe (Mediterranean Sea or Gulf of Cadiz). In contrast, the stronger genetic differentiation of M. oculata populations mirrors the effects of long‐term isolation in multiple refugia. We suggest that the distinct and genetically divergent, refugial populations initiated the post‐glacial recolonization of the northeastern Atlantic margins, leading to a secondary contact in the northern range and reaching higher latitudes much later, in the late Holocene. This study highlights the need to disentangle the influences of present‐day dispersal and evolutionary processes on the distribution of genetic polymorphisms, to unravel the influence of past and future environmental changes on the connectivity of cosmopolitan deep‐sea
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- 2019
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11. The Ecological Role of Patchy Cold-Water Coral Habitats: Does Coral Density Influence Local Biodiversity in Submarine Canyons of the Bay of Biscay?
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Menot, Lenaick, Van Den Beld, Inge, Arnaud-haond, Sophie, Bourillet, Jean-francois, Davies, J.s., Guillaumont, Brigitte, Olu, Karine, Menot, Lenaick, Van Den Beld, Inge, Arnaud-haond, Sophie, Bourillet, Jean-francois, Davies, J.s., Guillaumont, Brigitte, and Olu, Karine
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In the Bay of Biscay, Cold Water Coral (CWC) habitats have been mapped in 24 out of a hundred known submarine canyons. The footprint of ROV or towed-camera transects is small compared to the size of these canyons but still, known CWC habitats totalize a linear of 46 km. The distribution of these habitats, dominated by reef-building scleractinians, antipatharians, alcyonaceans and pennatulids, is however patchy and their median size is small, ranging from 6 to 65 m. While the preservation of these Vulnerable Marine Ecosystems has become essential, all CWC habitats will not be benefit from conservation strategies due to their widespread and patchy distribution. Priorities must thus be defined. Among the criteria for such prioritization, we explore here the ecological role of CWCs as ecosystem engineers.The abundance, the diversity and the taxonomic composition of megafaunal assemblages associated with each CWC habitat are compared. Scleractinian reefs, antipatharians and alcyonaceans on hard substrates as well as pennatulids on soft substrates host different megafaunal assemblages and each should be considered as separate management units. Within each of these three units, we further test the influence of coral cover or coral density, as well as the influence of patch size, on the abundance and the diversity of the associated fauna. In the different habitats, the megafauna shows different patterns according to coral cover, coral density and habitat size, suggesting that aggregations of CWCs do not all have the same ecological role within submarine canyons. The consequences for conservation prioritization are discussed.
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- 2018
12. Are trawl marks a good indicator of trawling pressure in muddy sand fishing grounds?
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Merillet, Laurene, Kopp, Dorothee, Robert, Marianne, Salaun, Michele, Mehault, Sonia, Bourillet, Jean-francois, Mouchet, Maud, Merillet, Laurene, Kopp, Dorothee, Robert, Marianne, Salaun, Michele, Mehault, Sonia, Bourillet, Jean-francois, and Mouchet, Maud
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The development of the vessel monitoring system (VMS) in the recent years has offered high-resolution data to map the distribution and intensity of fishing activities and contributed to enhancing the potential identification of fishing impacts. However, impacts could vary at very small scale and the resolution of VMS data might not be fine enough. Other proxy could be used, such as trawl marks visible on the seabed observed by underwater video or side-scan sonar to evaluate small-scale trawling effort. In the Bay of Biscay, an underwater video survey of the Nephrops norvegicus fishing ground was conducted and provided environmental characteristics such as depth and number of trawl marks at 152 transects. The relevance of observed trawl marks as a small-scale proxy of trawling effort was tested depending on the sediment type. The model showed a significant positive relation between density of marks and trawling effort for all sediments together but a different relation for each sediment type. Considering each sediment type separately, the unexpected high number of marks observed on sands could be linked with cohesive interactions between calcium carbonates particles while the low number of marks on fine lithoclastic muds could be due to sediment reworking and bioturbation. We conclude that the impact of trawling on the seabed varies with the type of sediments, hydrodynamic parameters, bioturbation and trawling intensity, leading to a very complex relationship. Trawl marks observed on video footage thus could be used as a proxy of trawling effort among the same type of sediment and not for fine lithoclastic muds.
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- 2018
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13. Le canyon de Capbreton : nouvelles approches morphostructurales et morphosédimentaires. Premiers résultats de la campagne Itsas
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Cirac, Pierre, Bourillet, Jean-François, Griboulard, Roger, and Normand, Alain
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- 2001
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14. Surconsolidation apparente et pression osmotique dans un sédiment marin
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Sultan, Nabil, Cochonat, Pierre, Dennielou, Bernard, Bourillet, Jean-François, Savoye, Bruno, and Colliat, Jean-Louis
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- 2000
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15. Structure et évolution récente de l’éventail turbiditique du Zaïre : premiers résultats scientifiques des missions d’exploration Zaïango1 & 2 (marge Congo–Angola)
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Savoye, Bruno, Cochonat, Pierre, Apprioual, Ronan, Bain, Olivier, Baltzer, Agnès, Bellec, Valérie, Beuzart, Paul, Bourillet, Jean-François, Cagna, Renaud, Cremer, Michel, Crusson, Alban, Dennielou, Bernard, Diebler, Daniel, Droz, Laurence, Ennes, Jean-Charles, Floch, Gilbert, Guiomar, Marie, Harmegnies, François, Kerbrat, René, Klein, Blandine, Kuhn, Helmuth, Landuré, Jean-Yves, Lasnier, Caroline, Le Drezen, Eliane, Le Formal, Jean-Pierre, Lopez, Michel, Loubrieu, Benoît, Marsset, Tania, Migeon, Sébastien, Normand, Alain, Nouzé, Hervé, Ondréas, Hélène, Pelleau, Pascal, Saget, Philippe, Séranne, Michel, Sibuet, Jean-Claude, Tofani, Roger, and Voisset, Michel
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- 2000
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16. Premières observations sur la morphologie et les processus sédimentaires récents de l’Éventail celtique
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AUFFRET, Gérard, ZARAGOSI, Sébastien, VOISSET, Michel, DROZ, Laurence, LOUBRIEU, Benoı̂t, PELLEAU, Pascal, SAVOYE, Bruno, BOURILLET, Jean-François, BALTZER, Agnès, BOURQUIN, Sylvie, DENNIELOU, Bernard, COUTELLE, Alain, WEBER, Nicolas, and FLOCH, Gilbert
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- 2000
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17. L'éventail profond de la marge celtique: stratigraphie et évolution sédimentaire
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Droz, Laurence, Auffret, Gérard A., Savoye, Bruno, and Bourillet, Jean-François
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- 1999
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18. Cold-water coral habitats in submarine canyons of the Bay of Biscay
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Van Den Beld, Inge, Bourillet, Jean-francois, Arnaud-haond, Sophie, De Chambure, Laurent, Davies, Jaime S, Guillaumont, Brigitte, Olu, Karine, Menot, Lenaick, Van Den Beld, Inge, Bourillet, Jean-francois, Arnaud-haond, Sophie, De Chambure, Laurent, Davies, Jaime S, Guillaumont, Brigitte, Olu, Karine, and Menot, Lenaick
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The topographical and hydrological complexity of submarine canyons, coupled with high substratum heterogeneity, make them ideal environments for cold-water coral (CWC) habitats. These habitats, including reefs, are thought to provide important functions for many organisms. The canyons incising the continental slope of the Bay of Biscay have distinct morphological differences from the north to the south. CWCs have been reported from this basin in the late 19th century; however, little is known about their present-day distribution, diversity and environmental drivers in the canyons. In this study, the characteristics and distribution of CWC habitats in the submarine canyons of the Bay of Biscay are investigated. Twenty-four canyons and three locations between adjacent canyons were sampled using a Remotely Operated Vehicle (ROV) or a towed camera system. Acquired images were annotated for habitat type (using the CoralFISH classification system), substrate cover and coral identification. Furthermore, the influence of hydrological factors and geomorphology on the CWC distribution was investigated. Eleven coral habitats, formed by 62 morphotypes of scleractinians, gorgonians, antipatharians and seapens, inhabiting hard and/or soft substrate, were observed. The distribution patterns were heterogenous at regional and local scales; the south Bay of Biscay and the southeastern flank favored soft substrate habitats. Biogenic and hard substrate habitats supported higher coral diversities than soft substrate habitats and had similar species compositions. A higher coral species turnover characterized soft substrate habitats. Substrate type was the most important driver of the patterns in both distribution and composition. Observations of coral reefs on steeper areas in the canyons and coral rubble on flatter areas on the interfluve/upper slope, support the hypothesis that canyons serve as refuges, being less accessible to trawling, although natural causes may also contribute to t
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- 2017
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19. A new classification scheme of European cold-water coral habitats: implications for ecosystem-based management of the deep sea
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Davies, J. S., Guillaumont, Brigitte, Tempera, Fernando, Vertino, A., Beuck, L., Olafsdottir, S. H., Smith, C. J., Fossa, J. H., Van Den Beld, Inge, Savini, A., Rengstorf, A., Bayle, Christophe, Bourillet, Jean-francois, Arnaud-haond, Sophie, Grehan, A., Davies, J. S., Guillaumont, Brigitte, Tempera, Fernando, Vertino, A., Beuck, L., Olafsdottir, S. H., Smith, C. J., Fossa, J. H., Van Den Beld, Inge, Savini, A., Rengstorf, A., Bayle, Christophe, Bourillet, Jean-francois, Arnaud-haond, Sophie, and Grehan, A.
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Cold-water coral (CWC) habitats can form complex structures which provide refuge, nursery grounds and physical support for a diversity of other living organisms, but despite their ecological significance, CWCs are still vulnerable to human pressures such as fishing, pollution, ocean acidification and global warming Providing coherent and representative conservation of vulnerable marine ecosystems including CWCs is one of the aims of the Marine Protected Areas networks being implemented across European seas and oceans under the EC Habitats Directive, the Marine Strategy Framework Directive and the OSPAR Convention. In order to adequately represent ecosystem diversity these initiatives require a standardised habitat classification that organises the variety of biological assemblages and provides consistent and functional criteria to map them across European Seas (Howell 2010). One such classification system, EUNIS, enables a broad level classification of the deep sea based on abiotic and geomorphological features. More detailed lower biotope-related levels are currently under-developed, particularly with regards deep-water habitats (>200 m depth). This paper proposes a hierarchical CWC biotope classification scheme that could be incorporated by existing classification schemes such as EUNIS. The scheme was developed within the EU FP7 project CoralFISH to capture the variability of CWC habitats identified using a wealth of seafloor imagery datasets from across European seas and oceans. Depending on the resolution of the imagery being interpreted, this hierarchical scheme allows data to be recorded from broad CWC biotope categories down to detailed taxonomy-based levels, thereby providing a flexible yet valuable information level for management. The CWC biotope classification scheme identifies 81 biotopes and highlights the limitations of the classification framework and guidance provided by EUNIS, the EC Habitats Directive, OSPAR and FAO; with limited categories for ide
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- 2017
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20. Marine litter in submarine canyons of the Bay of Biscay
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Van Den Beld, Inge, Guillaumont, Brigitte, Menot, Lenaick, Bayle, Christophe, Arnaud-haond, Sophie, Bourillet, Jean-francois, Van Den Beld, Inge, Guillaumont, Brigitte, Menot, Lenaick, Bayle, Christophe, Arnaud-haond, Sophie, and Bourillet, Jean-francois
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Marine litter is a matter of increasing concern worldwide, from shallow seas to the open ocean and from beaches to the deep-seafloor. Indeed, the deep sea may be the ultimate repository of a large proportion of litter in the ocean. We used footage acquired with a Remotely Operated Vehicle (ROV) and a towed camera to investigate the distribution and composition of litter in the submarine canyons of the Bay of Biscay. This bay contains many submarine canyons housing Vulnerable Marine Ecosystems (VMEs) such as scleractinian coral habitats. VMEs are considered to be important for fish and they increase the local biodiversity. The objectives of the study were to investigate and discuss: i) litter density, ii) the principal sources of litter, iii) the influence of environmental factors on the distribution of litter, and iv) the impact of litter on benthic communities. Litter was found in all 15 canyons and at three sites on the edge of the continental shelf/canyon, in 25 of 29 dives. The Belle-île and Arcachon Canyons contained the largest amounts of litter, up to 12.6 and 9.5 items 100 images−1 respectively. Plastic items were the most abundant (42%), followed by fishing-related items (16%). The litter had both a maritime and a terrestrial origin. The main sources could be linked to fishing activities, major shipping lanes and river discharges. Litter appeared to accumulate at water depths of 801–1100 m and 1401–1700 m. In the deeper of these two depth ranges, litter accumulated on a geologically structured area, accounting for its high frequency at this depth. A larger number of images taken in areas of coral in the shallower of these two depth ranges may account for the high frequency of litter detection at this depth. A larger number of litter items, including plastic objects in particular, were observed on geological structures and in coral areas than on areas of bare substratum. The distribution of fishing-related items was similar for the various types of relief. L
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- 2017
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21. Two “pillars” of cold-water coral reefs along Atlantic European margins: Prevalent association of Madrepora oculata with Lophelia pertusa, from reef to colony scale
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Arnaud-haond, Sophie, Van Den Beld, Inge, Becheler, Ronan, Orejas, C., Menot, Lenaick, Frank, N., Grehan, A., Bourillet, Jean-francois, Arnaud-haond, Sophie, Van Den Beld, Inge, Becheler, Ronan, Orejas, C., Menot, Lenaick, Frank, N., Grehan, A., and Bourillet, Jean-francois
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The scleractinian coral Lophelia pertusa has been the focus of deep-sea research since the recognition of the vast extent of coral reefs in North Atlantic waters two decades ago, long after their existence was mentioned by fishermen. These reefs where shown to provide habitat, concentrate biomass and act as feeding or nursery grounds for many species, including those targeted by commercial fisheries. Thus, the attention given to this cold-water coral (CWC) species from researchers and the wider public has increased. Consequently, new research programs triggered research to determine the full extent of the corals geographic distribution and ecological dynamics of “Lophelia reefs”. The present study is based on a systematic standardised sampling design to analyse the distribution and coverage of CWC reefs along European margins from the Bay of Biscay to Iceland. Based on Remotely Operated Vehicle (ROV) image analysis, we report an almost systematic occurrence of Madrepora oculata in association with L. pertusa with similar abundances of both species within explored reefs, despite a tendency of increased abundance of L. pertusa compared to M. oculata toward higher latitudes. This systematic association occasionally reached the colony scale, with “twin” colonies of both species often observed growing next to each other when isolated structures were occurring off-reefs. Finally, several “false chimaera” were observed within reefs, confirming that colonial structures can be “coral bushes” formed by an accumulation of multiple colonies even at the inter-specific scale, with no need for self-recognition mechanisms. Thus, we underline the importance of the hitherto underexplored M. oculata in the Eastern Atlantic, re-establishing a more balanced view that both species and their yet unknown interactions are required to better elucidate the ecology, dynamics and fate of European CWC reefs in a changing environment.
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- 2017
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22. Cold water corals of the Bay of Biscay: 8 bathymorphological and geomorphological maps at 1:100,000
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Bourillet, Jean-francois, De Chambure, Laurent, and Loubrieu, Benoit
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Les coraux d’eau froide, contrairement aux coraux tropicaux, n’ont pas besoin de lumière et peuvent se développer en profondeur. Les espèces constructrices comme Lophelia pertusa et Madrepora occulata ont une distribution mondiale et sont présentes de la Norvège à la Grèce sous forme de monts carbonatés ou de récifs. Menacés par l’évolution des conditions environnementales et les actions anthropiques, les coraux d’eau froide sont actuellement classés comme écosystème vulnérable par plusieurs institutions internationales. Dans les eaux européennes, les indicateurs pour mesurer l’impact des pêcheries et l’efficacité des mesures de protection manquent encore. Le projet européen CoralFISH vise à étudier l’interaction entre les coraux, les poissons et les pêcheries par une approche écosystémique. Un des objectifs de cette étude est de caractériser leurs habitats à partir des formes géologiques des fonds marins. Dans le golfe de Gascogne, les associations de coraux se situent principalement sur les flancs et le long des chutes des canyons. Différentes campagnes océanographiques menées dans ce but avec des sondeurs de haute technologie ont abouti à l’élaboration de cartes très précises de 4 secteurs de la marge septentrionale du golfe de Gascogne. Le document est un portefeuille de 4 cartes bathymorphologiques et 4 cartes géomorphologiques au 1/100.000. Elles apportent un regard nouveau sur le modelé de la pente continentale et le fonctionnement des canyons., 8 cartes au 1/100.000 : • Carte bathymorphologique du canyon de Blackmud au canyon de Douarnenez - format A0 • Carte géomorphologique du canyon de Blackmud au canyon de Douarnenez - format A0 • Carte bathymorphologique du canyon de Penmarc’h au canyon de Saint-Nazaire - format A0 • Carte géomorphologique du canyon de Penmarc’h au canyon de Saint-Nazaire - format A0 • Carte bathymorphologique du canyon des Sables d’Olonne au canyon d’Ars - format A0 • Carte géomorphologique du canyon des Sables d’Olonne au canyon d’Ars - format A0 • Carte bathymorphologique du canyon de Cap-Ferret au canyon d’Arcachon - format A0 • Carte géomorphologique du canyon de Cap-Ferret au canyon d’Arcachon - format A0 ISBN : 978-2-7592-1655-0
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- 2012
23. Comments to Westaway and Bridgland - 'Causes, consequences and chronology of large-magnitude palaeoflows in Middle and Late Pleistocene river systems of northwest Europe'
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Toucanne, Samuel, Zaragosi, S., Eynaud, F., Bourillet, Jean-francois, Lericolais, Gilles, and Gibbard, P. L.
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Westaway and Bridgland (Earth Surface Processes and Landforms 35: 1071–1094, 2010) discuss the causes, the consequences and the chronology of large-magnitude palaeoflows in Pleistocene river systems of northwest Europe. Based on their calculations, these authors suggest that the combined effects of meltwater from Alpine glaciers, rainfall, snowmelt and melting of permafrost during Heinrich Events (HEs) explain the large-magnitude discharges of the Fleuve Manche palaeoriver which punctuated the last glacial period. This comment identifies some approximations and inconsistencies regarding (i) the timing of the last massive Fleuve Manche palaeoriver discharge and its relation to the de-glacial pattern of the British-Irish Ice Sheet (Point 1); (ii) the palaeoclimatic conditions prevailing on land and the antagonistic forcing mechanism proposed by the authors to explain the large-magnitude palaeoflows (Point 2); (iii) Westaway and Bridgland's (2010) revised interpretation of the deep-sea records from the Bay of Biscay (Point 3); and (iv) the relationship between the offshore sedimentation since the Middle Pleistocene and the formation of the Dover Strait (Point 4). Each point is discussed.
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- 2011
24. Recopla : Inventaire de données de géosciences marines pour une cartographie moderne du plateau continental français
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Satra Le Bris, Catherine, Gautier, Emeric, and Bourillet, Jean-francois
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Knowledge of the French continental shelf is heterogeneous : the bathymetry of the french EEZ is well known for the deeper domain but insufficient to establish a reference state on the continental shelf. Recopla consists of a modern continental shelf mapping project in cooperation with the oceanographic and hydrographic service of the French Navy. It will contribute to increase the knowledge necessary to establish reference data for the French/European marine strategy. The first task of the Recopla project consisted of an inventory of the geophysical data and metadata available on the French continental shelf, and a classification of these data according the level of processing : raw, processed, interpreted, published. Combining this information with the data processed, interpreted and present as maps, it was possible to identify the achievements, but also to identify gaps and opportunities for advances in knowledge. The inventory also identified sectors with high growth potential as the Aquitaine shelf or the Gulf of Lions., La connaissance du plateau et de la pente continentale océanique (20% de l’océan mondial) est hétérogène : ponctuellement bien connue pour des thématiques particulières, la cartographie morpho-bathymétrique des fonds sous juridiction française est suffisante pour le domaine de la zone économique exclusive (ZEE) profonde métropolitaine, mais insuffisante pour justifier de l'extension au delà des 200 milles ou pour établir ne serait-ce qu'un état de référence sur le plateau continental et sur la majeure partie des DOM/TOM. Le SHOM et l'Ifremer, conscients de ce manque, ont initié des avants-projets et déposé ensemble un projet au Grenelle de la Mer. Cette fiche de reconnaissance des zones à enjeux du plateau continental a notamment été retenue par le Conseil Interministériel de la Mer, parmi les 16 points du relevé de décisions consistant à améliorer la connaissance de l'environnement marin. RECOPLA est un avant-projet de cartographie moderne du plateau continental initié par l'Ifremer. Il contribuera à renforcer la connaissance, à établir des données de référence utiles par exemple pour la Directive Cadre Européenne Stratégie pour le Milieu Marin (DCSMM, 2021) ou les Aires Marines Protégées. La première tâche du projet Recopla a été d’établir un inventaire des données de géosciences marines acquises sur le plateau continental métropolitain, en distinguant l’état des données, validées, traitées, publiées. En croisant ces informations avec les données traitées, interprétées et présentes sous forme de documents cartographiques, il a été possible d'identifier les acquis, mais également de déterminer les manques et les perspectives d'avancées de la connaissance. L’inventaire a aussi mis en évidence des secteurs à fort potentiel de progression comme le plateau aquitain ou le golfe du Lion.
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- 2011
25. ACTION RECOPLA - Inventaire et bancarisation des données de Géosciences Marines pour les façades Atlantique, Manche et Méditerranée
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Gautier, Emeric, Kerjean, Mathieu, Satra Le Bris, Catherine, and Bourillet, Jean-francois
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Méditerranée ,Englsih Channel ,sismique ,imagerie acoustique ,GeoBIS ,Inventory ,Inventaire ,Atlantique ,données brutes ,Manche ,SIG ,GIS ,interpreted data ,traitées ,Atlantic ,Mediterranean Sea ,seismic ,processed ,interprétées ,raw ,backscatter ,bathymétrie - Abstract
This report presents the inventory work realized for all the Marine Geoscience dept data acquired on the French continental shelf. It lists the bathymetric, seismic and backscattering data acquired, processed and interpreted in English Channel, Atlantic and Mediterranean. All the maps used for this inventory are available within the GIS "Manche Atlantique" and "Golfe du Lion"., Ce rapport présente le travail d’inventaire réalisé pour l’ensemble des données du département Géosciences Marines acquises sur le plateau métropolitain français. Il répertorie les différentes données bathymétriques, sismiques et d’imagerie acoustique acquises, traitées et interprétées pour les façades Manche, Atlantique et Méditerranée. L’ensemble des cartes utilisées pour réaliser cet inventaire est consultable à l’aide des SIG Manche Atlantique et Golfe du Lion.
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- 2010
26. Fluid emissions at the Aquitaine Shelf (Bay of Biscay, France): A biogenic origin or the expression of hydrocarbon leakage?
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Dupre, Stephanie, Berger, Laurent, Le Bouffant, Naig, Scalabrin, Carla, Bourillet, Jean-francois, Dupre, Stephanie, Berger, Laurent, Le Bouffant, Naig, Scalabrin, Carla, and Bourillet, Jean-francois
- Abstract
Fishery acoustic surveys conducted in the Bay of Biscay and dedicated to monitoring and predicting pelagic ecosystem evolution reveal numerous active seeps on the Aquitaine Shelf, east of the shelf break, at water depths ranging from 140 to 185 m. Some acoustic anomalies recorded in the water column with hull-mounted single and multibeam echosounders are clearly caused by fluid escape at the seabed, most likely gases. These fluid emissions are associated at the seafloor with high backscatter subcircular small-scale mounds, on average less than 2 m high and a few metres in diameter. Based on near-bottom video and acoustic surveys, these mounds are interpreted to be by-products of gas seepage, possibly methane-derived authigenic carbonates. The spatial distribution of the seeps and related structures, based on water column acoustic gas flares and high backscatter seabed patches, appears to be relatively broad, with a North–South extension of ~65 km across the Parentis Basin and the Landes High, and a West–East extension along a few kilometres wide on the shelf. The seepage activity seems persistent through time at the annual scale, with acoustic evidence dating back to 1998. The spatial distribution of the fluid emissions at the Aquitaine Shelf may suggest possible sedimentary and tectonic controls in relation with the Pyrenean compression phase. The nature and the origin of the emitted fluids and seafloor mounds are unknown. The gases may correspond to biogenic methane from Late Pleistocene deposits or to thermogenic gases originating from deeper, Jurassic–Cretaceous levels. The oil province of the Parentis Basin raises questions regarding possible genetic links to the petroleum system.
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- 2014
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27. Le canyon de Capbreton - Carte morpho-bathymétrique - Échelle 1/50 000
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Bourillet, Jean-francois, Augris, Claude, Cirac, Pierre, Maze, Jean-pierre, Normand, Alain, Loubrieu, Benoit, Crusson, Alban, Gaudin, Mathieu, Poirier, Dominique, Satra Le Bris, Catherine, Simplet, Laure, and Université Bordeaux 1 - Sciences Technologies
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morpho-bathymétrie ,morpho-bathymetry ,geology ,cartographie ,géologie ,canyon ,mapping - Abstract
The morpho-bathymetric mapping of the Capbreton canyon is based on the results of eight oceanographic surveys conducted between 1993 and 2004 on board the oceanographic vessels the Thalia and Le Suroit. The explored part of the canyon extends avers 150 km with a variation in level of 2 1OO m. lt features a deep embankment and a tier-shaped head. Bath documents published illustrate these features : a morpho-bathymetric map (2 sheets) to the scale 1/50 000 and a 30 relief map., La cartographie morpho-bathymétrique du canyon de Capbreton s'appuie sur les résultats de huit campagnes océanographiques effectuées entre 1993 et 2004, à bord des navires océanographiques de l'lfremer Thalia et Le Suroît. Dans sa partie reconnue, le canyon étend son cours sur 150 km et atteint 2 100 m de dénivelé; son fort encaissement, sa proximité de la côte et une tête en amphithéâtre permettent de le classer dans la catégorie des goufs. Les deux types de document édités illustrent ces caractéristiques : une carte morpho-bathymétrique en 2 feuilles à l'échelle 1/50 000 et une représentation en relief (30).
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- 2007
28. La Grande Vasière : architecture, mise en place et estimation des facteurs de son évolution
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Bourillet, Jean-francois, Dubrulle, Carole, Goubert, Evelyne, Jouanneau, Jean-marie, Cortijo, Elsa, Weber, Olivier, and Lesueur, Patrick
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Jean-François Bourillet1, Carole Dubrulle2&3, Evelyne Goubert4, Jean-Marie Jouanneau2, Elsa Cortijo5, Oliver Weber2, Patrick Lesueur3, Olivier Vicaire6 1 Ifremer-DRO/GM, Environnements sédimentaires, BP70, 29280 Plouzané 2 Université de Bordeaux I, DG0, CNRS-UMR 5005 EPOC, av. des facultés, 33405 Talence cedex 3 Université de Caen, UMR CNRS 6143 M2C, Centre de géomorphologie, rue des tilleuls, 14000 Caen 4 Université de Bretagne-Sud, LEMEL, Centre Y. Coppens, Campus de Tohannic, BP 573, 56017 Vannes 5 CNRS/CEA Laboratoire des Sciences du Climat et de l'Environnement, av. de la terrasse, 91198 Gif s/Yvette 6 Astérie, 36 quai de la Douane 29200 Brest La couverture holocène du plateau continental du golfe de Gascogne se développe au-dessus d’une pénéplaine résultant de l’érosion des dernières remontées marines. Son épaisseur plurimétrique s’explique par un faible taux de subsidence et un faible apport sédimentaire. Le plateau médian est occupé par la Grande Vasière. Des études géophysiques (Levron, 2002) et des prélèvements menés dans le cadre du Défi Golfe de Gascogne ont permis de déterminer la géométrie des sédiments meubles et d’estimer une séquence type : - Deux unités sableuses mises en place entre 22 et 11 ka BP avec l’unité inférieure plurimétrique de sable roux moyen à grossier carbonaté et l’unité supérieure plurimétrique de sable fin à moyen formant des structures Est-Ouest, - Une couche « superficielle » de quelques décimètres d’épaisseur de sable fin envasé et bioturbé. Elle est à l’origine de l’appellation « Grande Vasière » dorénavant mieux qualifiée par Grande Sablière. Sa mise en place débuterait suivant les secteurs entre 8.500 et 2000 ans BP. Seuls les secteurs Sud-Glénan au Nord et Rochebonne au Sud présentent une épaisseur plurimétrique, - Une couche d’interface millimétrique de vase récente. Les analyses sédimentologiques et isotopiques (210Pbexc et 234Thexc) des deux couches superficielles montrent que - la mince couche de vase est le témoin d’apport fluviatile récent, - la couche superficielle reflète un intense mélange sur une vingtaine de centimètres dû principalement aux activités biologiques, - un taux de sédimentation annuel de 2 mm , - une variabilité saisonnière liée à la fluctuation du front thermo-halin avec accumulation de matériel fin d’avril à septembre et remise en suspension en hiver (Dubrulle, 2003), - Les houles normales ou exceptionnelles entretiennent ou créent de fins « sillons » favorisant le mélange des unités sableuses héritées et de la fraction fine (Folliot, 2004). Des études sur l’évolution de la fraction fine sur 30 ans sont en cours. Dans le secteur Glénan, l’analyse des carottes (Folliot, 2004) indique que la mise en place (8,5 ka BP) s’est effectuée sous une tranche d’eau de 10 à 20 m et un contexte hydrodynamique énergétique (Goubert, 2004). Cette mise en place est suivie d’un évènement majeur trahi par une biocénose de Turitella communis à 8,2 ka cal BP. La cause pourrait être une perturbation du paléofront thermo-halin dont l’origine (connexion Manche-Mer du Nord ou rupture des grands lacs glaciaires nord-américains dans l’Atlantique nord) reste à préciser. Deux scénarios sont proposés : l’un pour la mise en place de la séquence sédimentaire en liaison avec la remontée du niveau marin au cours des 20.000 dernières années ; l’autre pour les cycles de dépôt/remise en suspension avec une estimation des forçages respectifs des tempêtes, des fleuves, de la bioturbation et des engins de pêche.
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- 2005
29. MD141 – ALIÉNOR. Rapport scientifique à bord du Marion Dufresne II
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Turon, Jean-louis, Bourillet, Jean-francois, Delpeint, Arnaud, and Simplet, Laure
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ALIENOR (A LIsbon-El Ferréol cruise. A support for North Oriental Atlantic Research) est l’intégration, dans une même campagne, de 4 projets situés sur la route du navire entre Lisbonne et Cardiff (leg 1) puis entre Cardiff et El Ferreol (leg 2). o PRIMAROSA (Paleoclimatic Research from Mediterranean Atlantic Record. Overflow Sedimentary Activity) projet de l’université de Bordeaux proposé par Jean-Louis TURON dont la première partie a été réalisée lors de la mission PRIVILEGE entre Malte et Lisbonne (Mai-Juin 2004). o SEQUOIA (Sequencing Ocean-Ice Interaction) financé par le NERC (Nature Environnement Research Council) et proposé par Ian HALL, principal investigateur. o ORSANE Oceanographic Record in the Sunart loch (Atlantic North East) présenté par Agnès Baltzer. o SEDICAR (SEDIment CARottage) projet présenté par Jean-François Bourillet (IFREMER) Jean-Louis TURON a été désigné par l’IPEV comme chef de Mission Coordinateur de l’ensemble des programmes. Ce document constitue un rapport préliminaire de la mission. Pour le premier leg, entre le 7 Juin 2004 (Lisbonne) et le 17 juin 2004 (Cardiff) ont été réalisées 21 opérations, soit 10 CALYPSO géant, 11 CALYPSO square (CASQ). Concernant la seconde partie, entre le 17 Juin 2004 (Cardiff) et le 24 Juin 2004 (El Ferrol), ont été réalisées 11 stations comprenant 2 CASQ, 8 CALYPSO et 1 gravitaire. 11 universités ou organismes français et 2 universités britanniques ont participé à cette partie. Au total 230 mètres de sédiments ont été récoltés. Seules les carottes MD04-2835 à MD04-2840, représentant la suite et fin de SEDICAR, figurent dans les annexes de ce rapport.
- Published
- 2004
30. The first estimation of Fleuve Manche palaeoriver discharge during the last deglaciation: Evidence for Fennoscandian ice sheet meltwater flow in the English Channel ca 20–18 ka ago
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Toucanne, Samuel, Zaragosi, Sébastien, Bourillet, Jean-François, Marieu, Vincent, Cremer, Michel, Kageyama, Masa, Van Vliet-Lanoë, Brigitte, Eynaud, Frédérique, Turon, Jean-Louis, and Gibbard, Philip L.
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- 2010
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31. Geomorphological classification in Bay of Biscay. Morpho-sedimentary mapping of the seabed in selected areas
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De Chambure, Laurent, Bourillet, Jean-francois, Bartel, Claire, De Chambure, Laurent, Bourillet, Jean-francois, and Bartel, Claire
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Les coraux d’eau froide, contrairement aux coraux tropicaux, n’ont pas besoin de lumière et peuvent se développer en profondeur. Les espèces constructrices comme Lophelia pertusa et Madrepora occulata ont une distribution mondiale et sont présentes de la Norvège à la Grèce sous forme de monts carbonatés ou de récifs. Menacés par l’évolution des conditions environnementales et les actions anthropiques, les coraux d’eau froide sont actuellement classés comme écosystème vulnérable par plusieurs institutions internationales. Dans les eaux européennes, les indicateurs pour mesurer l’impact des pêcheries et l’efficacité des mesures de protection manquent encore. Le projet européen CoralFish vise à étudier l’interaction entre les coraux, les poissons et les pêcheries par une approche écosystémique. Un des objectifs de cette étude est de caractériser leurs habitats à partir des formes géologiques des fonds marins.
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- 2013
32. Sur les traces des coraux d'eau froide du golfe de Gascogne. 8 cartes bathymorphologiques et géomorphologiques au 1/100.000
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Bourillet, Jean-francois, De Chambure, Laurent, Loubrieu, Benoit, Bourillet, Jean-francois, De Chambure, Laurent, and Loubrieu, Benoit
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Les coraux d’eau froide, contrairement aux coraux tropicaux, n’ont pas besoin de lumière et peuvent se développer en profondeur. Les espèces constructrices comme Lophelia pertusa et Madrepora occulata ont une distribution mondiale et sont présentes de la Norvège à la Grèce sous forme de monts carbonatés ou de récifs. Menacés par l’évolution des conditions environnementales et les actions anthropiques, les coraux d’eau froide sont actuellement classés comme écosystème vulnérable par plusieurs institutions internationales. Dans les eaux européennes, les indicateurs pour mesurer l’impact des pêcheries et l’efficacité des mesures de protection manquent encore. Le projet européen CoralFISH vise à étudier l’interaction entre les coraux, les poissons et les pêcheries par une approche écosystémique. Un des objectifs de cette étude est de caractériser leurs habitats à partir des formes géologiques des fonds marins. Dans le golfe de Gascogne, les associations de coraux se situent principalement sur les flancs et le long des chutes des canyons. Différentes campagnes océanographiques menées dans ce but avec des sondeurs de haute technologie ont abouti à l’élaboration de cartes très précises de 4 secteurs de la marge septentrionale du golfe de Gascogne. Le document est un portefeuille de 4 cartes bathymorphologiques et 4 cartes géomorphologiques au 1/100.000. Elles apportent un regard nouveau sur le modelé de la pente continentale et le fonctionnement des canyons., 8 cartes au 1/100.000 : • Carte bathymorphologique du canyon de Blackmud au canyon de Douarnenez - format A0 • Carte géomorphologique du canyon de Blackmud au canyon de Douarnenez - format A0 • Carte bathymorphologique du canyon de Penmarc’h au canyon de Saint-Nazaire - format A0 • Carte géomorphologique du canyon de Penmarc’h au canyon de Saint-Nazaire - format A0 • Carte bathymorphologique du canyon des Sables d’Olonne au canyon d’Ars - format A0 • Carte géomorphologique du canyon des Sables d’Olonne au canyon d’Ars - format A0 • Carte bathymorphologique du canyon de Cap-Ferret au canyon d’Arcachon - format A0 • Carte géomorphologique du canyon de Cap-Ferret au canyon d’Arcachon - format A0 ISBN : 978-2-7592-1655-0
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- 2012
33. Cenozoic tectonics of the Western Approaches Channel basins and its control of local drainage systems
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Le Roy, Pascal, Gracia-garay, Claire, Guennoc, Pol, Bourillet, Jean-francois, Reynaud, Jean-yves, Thinon, Isabelle, Kervevan, Patrick, Paquet, Fabien, Menier, David, Bulois, Cedric, Le Roy, Pascal, Gracia-garay, Claire, Guennoc, Pol, Bourillet, Jean-francois, Reynaud, Jean-yves, Thinon, Isabelle, Kervevan, Patrick, Paquet, Fabien, Menier, David, and Bulois, Cedric
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The geology of the Channel Western Approaches is a key to understand the post-rift evolution of the NW European continental margin in relation with the Europe/Africa collision. Despite considerable evidence of Tertiary tectonic inversion throughout the Channel basin, the structures and amplitudes of the tectonic movements remain poorly documented across the French sector of the Western Approaches. The effect of the tectonic inversion for the evolution of the "Channel River", the major system that flowed into the English Channel during the Plio-Quaternary eustatic lowstands, also needs to be clarified. Its drainage basin was larger than the present-day English Channel and constituted the source of terrigenous fluxes of the Armorican and Celtic deep sea fans. A lack of high-resolution seismic data motivated the implementation of the GEOMOC and GEOBREST cruises, whose main results are presented in this paper. The new observations highlight the diachronism and the contrast in amplitudes of the deformations involved in the inversion of the French Western Approaches. The tectonic inversion can be described in two stages: a paroxysmal Paleogene stage including two episodes, Eocene (probably Ypresian) and Oligocene, and a more moderate Neogene stage subdivided into Miocene and Pliocene episodes, driven by the reactivation of the same faults. The deformations along the North Iroise fault (NIF) located at the termination of the Medio-Manche fault produced forced folds in the sedimentary cover above the deeper faults. The tectonic inversion generated uplift of about 700 m of the mid-continental shelf south of the NIF. The isochron map of the reflectors bounding the identified seismic sequences clearly demonstrates a major structural control on the geometry of the Neogene deposits. First, the uplift of the eastern part of the Iroise basin during the upper Miocene favoured the onset of a broad submarine delta system that developed towards the subsiding NW outer shelf. The later
- Published
- 2011
34. Forward modeling for marine sediment characterization using chirp sonars
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Rakotonarivo, Sandrine, Legris, Michel, Desmare, Rozenn, Sessarego, Jean-pierre, Bourillet, Jean-francois, Rakotonarivo, Sandrine, Legris, Michel, Desmare, Rozenn, Sessarego, Jean-pierre, and Bourillet, Jean-francois
- Abstract
This paper investigates the forward modeling of chirp-sonar data for the quantitative characterization of marine subbottom sediment between 1 and 10 kHz. The forward modeling, based on a transfer function approach, included impacts of layering or impedance mismatch, attenuation, roughness, and transitional layers, i.e., continuous impedance variations. The presented approach provided the best compromise between the number of available geoacoustic parameters from chirp-sonar data and the subbottom modeling accuracy. The forward model was tested on deep-sea chirp-sonar data acquired at a central frequency of 3.5 kHz. Comparisons between synthetic and experimental seismograms showed good agreement for the first 15 m of buried layers. Performance of the inversion using this forward model was also examined through sensitivity analysis. The results suggested that estimations of layer thickness, impedance, and transitional layer thickness were robust, whereas roughness and attenuation estimations were subject to wavelength and layer thickness conditions.
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- 2011
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35. Timing of massive ‘Fleuve Manche’ discharges over the last 350 kyr: insights into the European ice-sheet oscillations and the European drainage network from MIS 10 to 2
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Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Cremer, M., Eynaud, Frederique, Van Vliet-lanoe, B., Penaud, A., Fontanier, C., Turon, J. L., Cortijo, E., Gibbard, P. L., Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Cremer, M., Eynaud, Frederique, Van Vliet-lanoe, B., Penaud, A., Fontanier, C., Turon, J. L., Cortijo, E., and Gibbard, P. L.
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Continuous high-resolution mass accumulation rates (MAR) and X-ray fluorescence (XRF) measurements from marine sediment records in the Bay of Biscay (NE Atlantic) have allowed the determination of the timing and the amplitude of the ‘Fleuve Manche’ (Channel River) discharges during glacial stages MIS 10, MIS 8, MIS 6 and MIS 4–2. These results have yielded detailed insight into the Middle and Late Pleistocene glaciations in Europe and the drainage network of the western and central European rivers over the last 350 kyr. This study provides clear evidence that the ‘Fleuve Manche’ connected the southern North Sea basin with the Bay of Biscay during each glacial period and reveals that ‘Fleuve Manche’ activity during the glaciations MIS 10 and MIS 8 was significantly less than during MIS 6 and MIS 2. We correlate the significant ‘Fleuve Manche’ activity, detected during MIS 6 and MIS 2, with the extensive Saalian (Drenthe Substage) and the Weichselian glaciations, respectively, confirming that the major Elsterian glaciation precedes the glacial MIS 10. In detail, massive ‘Fleuve Manche’ discharges occurred at ca 155 ka (mid-MIS 6) and during Termination I, while no significant discharges are found during Termination II. It is assumed that a substantial retreat of the European ice sheet at ca 155 kyr, followed by the formation of ice-free conditions between the British Isles and Scandinavia until Termination II, allowed meltwater to flow northwards through the North Sea basin during the second part of the MIS 6. We assume that this glacial pattern corresponds to the Warthe Substage glacial maximum, therefore indicating that the data presented here equates to the Drenthe and the Warthe glacial advances at ca 175–160 ka and ca 150–140 ka, respectively. Finally, the correlation of our records with ODP site 980 reveals that massive ‘Fleuve Manche’ discharges, related to partial or complete melting of the European ice masses, were synchronous with strong decreases in both th
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- 2009
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36. What forced the collapse of European ice sheets during the last two glacial periods (150 ka BP and 18 ka cal BP)? Palynological evidence
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Penaud, A., Eynaud, F., Turon, J. L., Zaragosi, S., Malaize, B., Toucanne, Samuel, Bourillet, Jean-francois, Penaud, A., Eynaud, F., Turon, J. L., Zaragosi, S., Malaize, B., Toucanne, Samuel, and Bourillet, Jean-francois
- Abstract
We present a new marine palynological record from the temperate North-eastern Atlantic (core MD03-2692, Celtic-Armorican margin) in the area of influence of the 'Fleuve Manche' paleoriver during glacial times. The runoff of this paleoriver was connected to the glacial history of European ice sheets (including the British Irish Ice Sheet-BIIS). Our study conducted on dinoflagellate cysts assemblages over the last 200 ka, associated with quantification of palynological remains reflecting continental influence (pre-Quaternary dinocysts and micro-algae Pediastrum spp. coenobia), yields detailed insights into the sea-surface paleoenvironments of this sector. More specifically, mechanisms responsible for the origin of unusual deposits of laminated sequences found at the end of Marine Isotope Stage (MIS) 2 and within mid-MIS 6 are here constrained. We provide evidence of genetic similarities between fluvial discharges occurring before and during times of deposition of the laminated deposits. Our study clarifies the causes of the collapse of European glaciated systems. At the end of MIS 2, prior to the deposition of the laminated deposits, plenioceanic influence characterized by high concentrations of Quaternary dinocysts prevailed, and a dinocyst species tracing the penetration of the warm North Atlantic Drift into the Bay of Biscay is recorded. However, this scenario did not recur prior to the deposition of laminated sediments of mid-MIS 6. In addition, contrary to the laminated deposits found at the end of MIS 2 and directly associated with Termination I, MIS 6 laminae appeared 20 ka earlier than Termination II. Our work shows that, during the penultimate glacial stage, the collapse of mid-latitudes ice sheets around 170 ka B.P. may have immediately followed the MIS 6.5 warming phase. Then, the most important melting event around 150 ka B.P. may be linked to a peak in insolation at 65 degrees N, though less important than those during MIS 6.5 and Termination II.
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- 2009
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37. First observations of deep-sea coral reefs along the Angola margin
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Le Guilloux, E., Olu, Karine, Bourillet, Jean-francois, Savoye, Bruno, Iglesias, S. P., Sibuet, Myriam, Le Guilloux, E., Olu, Karine, Bourillet, Jean-francois, Savoye, Bruno, Iglesias, S. P., and Sibuet, Myriam
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The West African continental slope is an important theatre for geological survey prospecting and drilling for hydrocarbons but little is known about local deep-sea biological communities at these depths. While shallow-water reefs are common and well-known features in the tropics, only few records of deep-water corals exist at low latitudes, and most of them have been reported by historical oceanographic cruises undertaking circum-navigations of the world. This study, based on a multi-disciplinary approach, presents a description of newly discovered deep-water coral reef communities along the Angola margin. Data from ROV, multibeam bathymetry, side-scan sonar and seismics from a deep-towed acoustic system (SAR) were used to describe the morphology of the coral mounds and their relationship with the local geological setting. The reef-building scleractinian coral Lophelia pertusa has colonised carbonate mounds that reach heights of ca. 30 in and follow an orientation that is correlated with salt tectonic processes. Recent erosion is suggested as a process that influences the shape of the mounds. Sixteen fish taxa were identified during the ROV video surveys, with some of them likely to have a strong affinity with dense-living corals. The species observed belong to families commonly associated with deep-water corals (i.e. Sebastidae, Berycidae, Lophiidae and Chaunacidae), except an abundant species belonging to the family Zoarcidae, rarely observed in this type of environment. Lucinidae shells were found around mounds. As this bivalve family is indicative of reduced sediment and generally associated with cold-seep environments, this finding could revive the debate over the relationship between the distribution of cold-water coral habitat and gas seeps. However, there is no present-day nutritional relationship between living coral and chemosynthetic-derived biomass. The possible role of fluid expulsion in carbonate precipitation acting as the first step for coral colonis
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- 2009
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38. A 1.2 Ma record of glaciation and fluvial discharge from the West European Atlantic margin
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Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Gibbard, P. L., Eynaud, F., Giraudeau, J., Turon, J. L., Cremer, M., Cortijo, E., Martinez, P., Rossignol, L., Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Gibbard, P. L., Eynaud, F., Giraudeau, J., Turon, J. L., Cremer, M., Cortijo, E., Martinez, P., and Rossignol, L.
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The correlation of continental sedimentary records with the marine isotope stratigraphy is a challenge of central importance in Quaternary stratigraphy, particularly in Western Europe where long records of glaciation on land areas are particularly rare. Here we demonstrate for the first time the interrelationship of events during the last 1.2 Ma in an ocean-sediment core from the Bay of Biscay (NE Atlantic), SW of the Channel. The identification of discharge variations from tributary river systems to the 'Fleuve Manche' palaeoriver during glacio-eustatic sea-level lowstands demonstrates the correlation of the marine sediment stratigraphy to the expansion and recession of the European ice-sheets. The amplitude and chronology of European ice-sheet oscillations since the late Early Pleistocene is discussed and our results demonstrate that the first coalescence of the Fennoscandian and British ice-sheets in the North Sea basin ca 450 ka ago caused a profound change in lowstand European drainage alignment. This change caused a rerouting of Fennoscandian and eastern British ice-sheets-derived meltwaters from northwards into the Nordic Seas to southwards into the eastern North Atlantic thereafter. Besides allowing a thorough synchronisation of the European ice-sheet palaeogeography with the well-dated records of palaeoceanographical changes, our results improve the stratigraphy of the English Channel palaeovalleys and will provide important constraints on paleoclimatic scenarios considering the impact that such rerouting and meltwater surges might have on the stability of the oceanic conveyor belt.
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- 2009
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39. Activity of the turbidite levees of the Celtic-Armorican margin (Bay of Biscay) during the last 30,000 years: Imprints of the last European deglaciation and Heinrich events
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Toucanne, Samuel, Zaragosi, S, Bourillet, Jean-francois, Naughton, F, Cremer, M, Eynaud, F, Dennielou, Bernard, Toucanne, Samuel, Zaragosi, S, Bourillet, Jean-francois, Naughton, F, Cremer, M, Eynaud, F, and Dennielou, Bernard
- Abstract
High-resolution sedimentological and micropaleontological studies of several deep-sea cores retrieved from the levees of the Celtic and Armorican turbidite systems (Bay of Biscay - North Atlantic Ocean) allow the detection of the major oscillations of the British-Irish Ice Sheet (BIIS) and 'Fleuve Manche' palaeoriver discharges over the last 30,000 years, which were mainly triggered by climate changes. Between 30 and 20 cal ka, the turbiditic activity on the Celtic-Annorican margin was weak, contrasting with previous stratigraphic models which predicted a substantial increase of sediment supply during low sea-level stands. This low turbidite deposit frequency was most likely the result of a weak activity of the 'Fleuve Manche' palaeoriver and/or of a reduced seaward transfer of sediments from the shelf to the margin. However, two episodes of turbiditic activity increase were detected in the Celtic-Armorican margin, during Heinrich events (HE) 3 and 2. This strengthening of the turbiditic activity was triggered by the meltwater releases from European ice sheets and glaciers favouring the seaward transfer of subglacial material, at least via 'Fleuve Manche' palaeoriver. At around 20 cal ka, a significant increase of turbidite deposit frequency occurred as a response to the onset of the last deglaciation. The retreat of the European ice sheets and glaciers induced a substantial increase of the 'Fleuve Manche' palaeoriver discharges and seaward transfer of continentally-derived material into the Armorican turbidite system. The intensification of the turbiditic activity on the Celtic system was directly sustained by the widespread transport of subglacial sediments from the British-Irish Ice Sheet (BIIS) to the Celtic Sea via the Irish Sea Basin. A sudden reduction of turbiditic activity in the Armorican system, between ca. 19 and 18.3 cal ka, could have been triggered by the first well known abrupt sea-level rise ('meltwater pulse', at around 19 cal ka) favouring the tra
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- 2008
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40. Behaviour Of A Piston Corer From Accelerometers And New Insights On Quality Of The Recovery
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Bourillet, Jean-francois, Damy, Gilbert, Dussud, Loic, Sultan, Nabil, Woerther, Patrice, Migeon, Sebastien, Bourillet, Jean-francois, Damy, Gilbert, Dussud, Loic, Sultan, Nabil, Woerther, Patrice, and Migeon, Sebastien
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Various observations pointed out that cores performed with gravity piston corer show signifi cant distortions mainly located at the top of the core. A series of 15 cores were performed at the same location on a submarine sand wave (Var canyon, France). Six different settings of the corer – three freefall heights and three slacks of the piston cable – were tested, including duplicates. Two accelerometers recorded simultaneously the movements of the core tube and the movements of the triggering arm. Then the z displacements were obtained by a double integration versus time of the measured acceleration. The analyses of results allowed the authors to estimate the amplitude and the duration of the elastic recoil of the aramid cable, andto distinguish four steps during the 4 seconds of penetration, including a distortion phase followed by a normal sampling phase linked to the status of the piston. The analyses of the quality and benchmark layers from recovered cores highlight the major role of the piston driven by the lengths of the counterweight and piston cables. The recovered thickness of a given layer can vary from 0.8 to 1.3 depending to the settings. A cone penetrometer test (CPT) trial at the same location gives a good estimation of the absolute geometry of the layers. The settings for cores with geotechnical purpose (better quality) will be different from settings for cores with sedimentological or palaeoclimatological purposes (better geometry). A compromise is proposed.
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- 2007
41. Long-term and millennial-scale climate variability in northwestern France during the last 8850 years
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Naughton, F, Bourillet, Jean-francois, Fernanda, M, Turon, J, Jouanneau, J, Naughton, F, Bourillet, Jean-francois, Fernanda, M, Turon, J, and Jouanneau, J
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Vegetation and quantitative climate reconstructions from a northwestern France shelf core (VK0358Bis) show orbital and suborbital climate variability for the last 8850 years in this region. A long-term cooling trend in summer temperatures, marked by gradual temperate and humid forest decline, parallels cooling in Greenland and the decrease of mid-latitude summer insolation reduction until at least 2000 cal. yr BP. At the long-term scale, the lowering in seasonal contrast revealed by vegetation changes follows the increase of precession. Corylus woodlands spread at the expense of deciduous Quercus forest, between 8740 and 8390 cal. yr BP, linked with the high seasonality conditions that, counterbalancing the long-term astronomical forcing trend, were amplified by the north Atlantic high-latitudes winter sea-ice expansion. High seasonality conditions resulted from the Agassiz and Ojibway final outburst episodes and consequent gradual reduction of the Meridional Overturning Circulation (MOC). Between 8390-8060 cal. yr BP, a sudden Corylus woodland decline marks the 8.2 kyr cold event in northwestern France probably triggered by the severe MOC reduction leading to the additional drop in winter temperature over Europe and Greenland. Nonetheless, seasonality remains high during this interval. The high seasonality conditions detected in 'VK03-58Bis' between 8740 and 8060 cal. yr BP reflects the multicentennial-scale climate cooling 8.6-8.0 kyr episode of the North Atlantic. Following the Agassiz and Ojibway final outburst episodes, climate became more stable. However, millennial-scale climate cooling episodes are recorded in 'VK03-Bis' and are characterized by weak winter cooling and increases in precipitation. Furthermore, dinocyst analysis and benthic gastropod Turritella communis occurrences indicate regional changes such as the southward migration of the Boreal biogeographical zone between 8740 and 8480 cal. yr BP and the subsequent opening of the English Channel at ar
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- 2007
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42. Nature and rates of fine-sedimentation on a mid-shelf: 'La Grande Vasiere' (Bay of Biscay, France)
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Dubrulle, C, Jouanneau, J, Lesueur, P, Bourillet, Jean-francois, Weber, O, Dubrulle, C, Jouanneau, J, Lesueur, P, Bourillet, Jean-francois, and Weber, O
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The study area, "La Grande Vasiere" (LGV), stretches out on the French Atlantic continental shelf (at ca. 100 m water depth), along 250 km from the Glenan Islands at the north to the southwest of Rochebonne at the south. Box-cores were sampled in this mid-shelf area during four cruises in June 1995, and in April, June and September 2002. They were investigated using sedimentologicat approaches (X-radiographs and grain-size analyses) and radionuclide studies (Pb-210 geochronology and excess Th-234). The main results are: (1) the surficial sediments are generally organized into a decimetrescale fining up sequence which can be the result of extreme storms; (2) an upper mixing layer of 7-20cm reflects an important biological benthic activity and/or the impact of fishing (i.e. trawlers); (3) a thin (i.e. a few mm) surficial mud-rich layer is the result of the present-day sedimentation; (4) an apparent annual sedimentation rate of 1-3 mm is recorded in several loci of the study area. Some seasonal variations appear, corresponding to the deposition of fine material from April to September, and to the reworking and the re-suspension during the winter. This fine material is the result of the decantation of estuarine plumes, mainly the Loire and the Vilaine rivers, over the study area. LGV ties (1) under the influence of a winter-to-spring thermo-hatine wedge that acts as a filter for the transfer of fine river-borne material to the slope and the open sea, and (2) below water depths where the mean swell action permits sedimentation, mainly in summer. From the point of view of the nature of its sediments, LGV is not a mud-belt, but a heterolithic and patchy sandy area that is submitted to increasing silting with environmental changes, on a seasonal-time scale. (c) 2007 Elsevier Ltd. All rights reserved.
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- 2007
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43. Deglacial laminated facies on the NW European continental margin: The hydrographic significance of British-Irish Ice Sheet deglaciation and Fleuve Manche paleoriver discharges
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Eynaud, F, Zaragosi, S, Scourse, J, Mojtahid, M, Bourillet, Jean-francois, Hall, I. R., Penaud, A, Locascio, M, Reijonen, A, Eynaud, F, Zaragosi, S, Scourse, J, Mojtahid, M, Bourillet, Jean-francois, Hall, I. R., Penaud, A, Locascio, M, and Reijonen, A
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[1] We have compiled results obtained from four high sedimentation rate hemipelagic sequences from the Celtic sector of the NW European margin ( NE Atlantic) to investigate the paleoceanographic and paleoclimatic evolution of the area over the last few climatic cycles. We focus on periods characteristic of deglacial transitions. We adopt a multiproxy sedimentological, geochemical, and micropaleontological approach, applying a sampling resolution down to ten microns for specific intervals. The investigation demonstrates the relationships between the Bay of Biscay hydrography and the glacial/deglacial history of both the proximal British-Irish Ice Sheet (BIIS) and the western European continent. We identify recurrent phases of laminae deposition concurrent with major BIIS deglacial episodes in all the studied cores. Evidence for abrupt freshwater discharges into the open ocean highlights the influence of such events at a regional scale. We discuss their impact at a global scale considering the present and past key location of the Bay of Biscay versus the Atlantic Meridional Overturning Circulation (AMOC).
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- 2007
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44. Inventaire des ressources en matériaux marins : Façades « Manche-Est » et « Loire-Gironde »
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Augris, Claude, Simplet, Laure, Maze, Jean-pierre, Morvan, Laetitia, Satra Le Bris, Catherine, Fitamant, Nadege, Bourillet, Jean-francois, Stephan, Michele, Augris, Claude, Simplet, Laure, Maze, Jean-pierre, Morvan, Laetitia, Satra Le Bris, Catherine, Fitamant, Nadege, Bourillet, Jean-francois, and Stephan, Michele
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Le présent rapport expose les résultats relatifs à ces trois phases. Une autre partie, préambule à la cinquième étape du projet, sera consacrée à la mise en forme des résultats et l’élaboration de la base de données sous Système d’Information Géographique pour les deux façades concernées « Manche-Est » et « Loire-Gironde ». Enfin, cinq cartes hors texte accompagnent ce rapport : · inventaire des ressources en matériaux marins, façade « Manche-Est » - Travaux réalisés (échelle 1/250 000, deux feuilles) ; · inventaire des ressources en matériaux marins, façade « Manche-Est » - Épaisseur des sédiments meubles (paléo-chenaux) (échelle 1/250 000, deux feuilles) ; · inventaire des ressources en matériaux marins, façade « Manche-Est » - Épaisseur des sédiments meubles (bancs sableux) (échelle 1/250 000, deux feuilles) ; · inventaire des ressources en matériaux marins, façade « Loire-Gironde » - Travaux réalisés (échelle 1/250 000) ; · inventaire des ressources en matériaux marins, façade « Loire-Gironde » - Épaisseur des sédiments meubles (paléo-chenaux) (échelle 1/250 000).
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- 2006
45. 'La Grande Vasière' mid-shelf mud belt : Holocene sedimentary structure, natural and anthropogenic impacts
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Bourillet, Jean-francois, Jouanneau, J.m., Macher, Claire, Le Hir, Pierre, Naughton, F, Bourillet, Jean-francois, Jouanneau, J.m., Macher, Claire, Le Hir, Pierre, and Naughton, F
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The Quaternary sequence of the Armorican continental shelf in the Bay of Biscay is setting down above one regional erosion surface, which has been produced by successive transgressions that occurred during the last deglaciations. The few meters of the sequence covers the Holocene period and it is composed by two clean and sandy units at the base followed by thin (few decimetres) clayed sand unit and mud (few millimetres) unit in the top. The two upper units form the improperly called "La Grande Vasière" area over 8,000 km2. The settlement of these sedimentary units occurred since 8,000 C14 years BP, previously to other coastal mud fields setting of the shelf. Historical grain size data show that the mud field has lost part of the fine content during the last 30 years. "La Grande Vasière" evolves at the rhythm of the cycles of deposition and remobilization. Fluvial supplies and tide currents are the major control factors of the deposition. Bioturbation enhances the homogenization of the surficial sediments. Waves and anthropogenic actions are the main factors for the remobilization of the fine particles. The action of both the storms and the bottom trawls are tentatively quantified.
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- 2006
46. Instabilities and deformation in the sedimentary cover on the upper slope of the southern Aquitaine continental margin, north of the Capbreton canyon (Bay of Biscay)
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Gonthier, E, Cirac, P, Faugeres, J, Gaudin, Mathieu, Cremer, M, Bourillet, Jean-francois, Gonthier, E, Cirac, P, Faugeres, J, Gaudin, Mathieu, Cremer, M, and Bourillet, Jean-francois
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Acoustic and core data have recently been collected on the shelf break and the upper part of the slope of the south Aquitaine continental margin. They reveal the major role played by mass-flow gravity processes in deposit erosion and redistribution, modelling of the sea-bed, and transfer of sediment toward the deep-sea. The study region is bounded in the south by the Capbreton canyon. The northern area, which shows a smooth morphology, is characterised by small-scale deformations due to sediment creep or low-amplitude slide processes. The deformations are associated with mini listric-like faults that bound packets of sediments in which the deposit geometry is typical of constructional sediment waves. These sediment waves result from the interaction of depositional and gravity deformation processes. In the southern area, closer to the canyon, wave-like structures are still present but mostly of smaller size. They only result from gravity deformation processes without any evidence of constructional processes. In the vicinity of the Capbreton canyon, the shelf break and upper slope have a much more uneven morphology with sedimentary reliefs, escarpments and depressions directed toward the canyon thalweg. The depressions look like slide scars, and could be the result of regressive slides initiated at the top of the canyon flank. The age of the sliding event responsible for the formation of the depression observed today could be middle to upper Quaternary. Since their formation, these depressions act as conduits that channel the transfer of shelf sediment into the canyon, as demonstrated by the occurrence of a meandering channel on the sea-floor of one depression.
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- 2006
47. The French Atlantic margin and deep-sea submarine systems
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Bourillet, Jean-francois, Zaragosi, S, Mulder, T, Bourillet, Jean-francois, Zaragosi, S, and Mulder, T
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The sedimentary infill of the Bay of Biscay off Ireland, UK, France and Spain took place in four phases. The last one (35 Ma to present) is characterised by gravitational, pelagic, contouritic and glacigenic processes leading to the setup of three deep sea systems. To the North, the Celtic and Armorican fans are fed by a "canyon-dominated" margin and its connection with the "Manche" palaeoriver, which drained a large area of western Europe. To the South, the Cap-Ferret fan results from the evolution of a "tectonic-dominated" margin and the erosion of the Pyrenee mountains.
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- 2006
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48. The impact of the last European deglaciation on the deep-sea turbidite systems of the Celtic-Armorican margin (Bay of Biscay)
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Zaragosi, Sébastien, Bourillet, Jean-francois, Eynaud, Frédérique, Toucanne, Samuel, Denhard, Benjamin, Van Toer, Aurélie, Lanfumey, Valentine, Zaragosi, Sébastien, Bourillet, Jean-francois, Eynaud, Frédérique, Toucanne, Samuel, Denhard, Benjamin, Van Toer, Aurélie, and Lanfumey, Valentine
- Abstract
The compilation of results obtained on three giant piston cores from the Whittard, Shamrock and Guilcher turbidite levees reveals a high-resolution stratigraphic record for the Bay of Biscay. Due to the abundance of reworked sediments in these sedimentary environments, a specific methodological approach, based on an X-ray-assisted subsampling phase associated with sedimentological, geochemical and micropalaeontological analyses, was implemented. With an accurate chronological framework, this multi-proxy investigation provides observations on the 'Fleuve Manche' palaeoriver and the British-Irish Ice Sheet (BIS) histories over the last 20,000 years. The results obtained highlight the direct influence of the decay of the BIS on the Bay of Biscay deep-sea clastic sedimentation during the last European deglacial phase. During this period, the annual BIS cycle of meltwater seems enough to generate seasonal turbidity currents associated with exceptional sedimentation rates in all the Celtic and Armorican turbidite systems. With very high sedimentation rates, the turbidite levees represent the main deep-sea clastic depositional area. Long coring combined with a very careful subsampling method can provide continuous high-resolution palaeoenvironmental signals.
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- 2006
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49. ROV study of a giant pockmark on the Gabon continental margin
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Ondreas, Helene, Olu, Karine, Fouquet, Yves, Charlou, Jean-luc, Gay, Aurelien, Dennielou, Bernard, Donval, Jean-pierre, Fifis, Alexis, Nadalig, Thierry, Cochonat, Pierre, Cauquil, E, Bourillet, Jean-francois, Le Moigne, Morgan, Sibuet, Myriam, Ondreas, Helene, Olu, Karine, Fouquet, Yves, Charlou, Jean-luc, Gay, Aurelien, Dennielou, Bernard, Donval, Jean-pierre, Fifis, Alexis, Nadalig, Thierry, Cochonat, Pierre, Cauquil, E, Bourillet, Jean-francois, Le Moigne, Morgan, and Sibuet, Myriam
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A giant, 800-m wide pockmark, called Regab, was discovered along the Equatorial African margin at 3160-m water depth and was explored by remote operated vehicle (ROV) as part of the Zaiango (1998-2000) and Biozaire (2001-2003) projects carried out conjointly by TOTAL and a number of French research institutes. A microbathymetric map obtained using the ROV sensors shows that the pockmark actually consists of a cluster of smaller pockmarks aligned N70 along a 15-m deep depression. Methane was recorded all over the pockmark, the highest values along the axis of the depression where massive carbonate crusts and dense seep communities were also found. Several faunal species belong to the Vesicomyidae and Mytilidae bivalve families, as well as to Siboglinidae (Vestimentifera) tubeworms. Preliminary analyses confirm their association with symbiotic bacteria, thus documenting their dependence on fluid seeps. The pockmark appears to be related to an infilled channel, visible on the seismic data 300 in below the seafloor, which may act as a reservoir for biogenic fluids supplied to the trap from the surrounding sediments.
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- 2005
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50. Understanding continent-ocean sediment transfer
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Mulder, Thierry, Cirac, Pierre, Gaudin, Mathieu, Bourillet, Jean-francois, Trainer, J., Normand, Alain, Weber, O., Griboulard, R., Jouanneau, Jean-marie, Anschutz, Pierre, Jorissen, Frans, Mulder, Thierry, Cirac, Pierre, Gaudin, Mathieu, Bourillet, Jean-francois, Trainer, J., Normand, Alain, Weber, O., Griboulard, R., Jouanneau, Jean-marie, Anschutz, Pierre, and Jorissen, Frans
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Submarine canyons are narrow but deep submarine valleys that extend for hundreds of meters. They represent the most impressive structures that shape the present morphology of passive continental margins. They can occur off the mouth of rivers: the Tagus, Zaire, Amazon, and Orinoco in the Atlantic; the Indus in the Indian Ocean; and the Var, Rhone, and Ebro in the Mediterranean. Some are at times disconnected from any stream mouth such as the Nazare canyon, off Portugal, despite the fact that it is close to the coast. Some were connected to a river mouth during lowstands of sea level, such as the Wilmington canyon in the northwest Atlantic, or the Blackmud canyon in the northeast Atlantic.
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- 2004
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