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Registros recuperados: 14
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A benthic Si mass balance on the Congo margin: Origin of the 4000 m DSi anomaly and implications for the transfer of Si from land to ocean ArchiMer
Ragueneau, O.; Regaudie-de-gioux, A.; Moriceau, B.; Gallinari, M.; Vangriesheim, Annick; Baurand, F.; Khripounoff, Alexis.
To elucidate the origin of the silicic acid (DSi) anomaly observed along the 4000 isobath on the Congo margin, we have established a benthic Si mass balance and performed direct measurements of biogenic silica (bSiO(2)) dissolution in the deep waters and in the sediments. Results strongly suggest that the anomaly originates from the sediments; the intensity of DSi recycling is consistent with the degradation of organic matter, as observed from Si:O-2 ratios in the benthic fluxes compared to that ratio observed in the anomalies. Strong imbalances, observed in both the Si and C mass balances, suggest that the biogenic matter that degrades and dissolves in these sediments near 4000 m does not come from pelagic sedimentation. It is probably not coming also...
Tipo: Text Palavras-chave: Congo; Continental margin; Preservation; Dissolution; Biogenic silica.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-7410.pdf
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A First Look at Dissolved Ge Isotopes in Marine Sediments ArchiMer
Baronas, J. Jotautas; Hammond, Douglas E.; Rouxel, Olivier; Monteverde, Danielle R..
The removal of chemical species from seawater during the precipitation of authigenic minerals is difficult to constrain but may play a major role in the global biogeochemical cycles of some elements, including silicon (Si) and germanium (Ge). Here, we present Ge/Si, δ74Ge, and supporting chemical data of pore waters and core incubations at three continental margin sites in California and the Gulf of Mexico. We used these data to partition Ge release and uptake by the various allogenic (delivered via sedimentation) and authigenic (formed in situ) phases in these sediments. About half of the pore water Ge (δ74Gepw = 1.3–2.4‰) is supplied by biogenic silica dissolution (δ74Ge ~ 3‰), with the other half contributed by lithogenic particulates (δ74Ge ~ 0.6‰)....
Tipo: Text Palavras-chave: Germanium; Biogenic silica; Authigenesis; Fe oxides; Isotope fractionation; Continental margin.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00504/61556/65466.pdf
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Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake - art. no. L043111 ArchiMer
Deverchere, Jacques; Yelles, K; Domzig, Anne; Mercier De Lepinay, B; Bouillin, J.p.; Gaullier, V; Bracene, R; Calais, E; Savoye, Bruno; Kherroubi, A; Le Roy, P; Pauc, H; Dan, Gabriela.
[1] We investigate the active seismogenic fault system in the area of the 2003 Mw 6.9 Boumerdes earthquake, Algeria, from a high-resolution swath bathymetry and seismic survey. A series of 5 main fault-propagation folds similar to20-35 km long leave prominent cumulative escarpments on the steep slope and in the deep basin. Fault activity creates Plio-Quaternary growth strata within uplifted areas such as a rollover basin on the slope and piggyback basins in the deep ocean. Most thrusts turn to fault-propagation folds at the sub-surface and depict ramp-flat trajectories. We find that the two main slip patches of the 2003 Mw 6.9 Boumerdes earthquake are spatially correlated to two segmented cumulative scarps recognized on the slope and at the foot of the...
Tipo: Text Palavras-chave: Continental margin; Sismicity; Tectonophysics.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-743.pdf
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Biogeochemical transformations of dissolved organic matter at the sediment-water interface: results from in situ incubations within benthic chambers ArchiMer
Accornero, A; Picon, P; De Bovee, F.
Biogeochemical transformations of dissolved organic matter at the sediment-water interface were investigated by the use of benthic chambers in the western Gulf of Lions. The experimental approach used for this study consisted of in situ incubations of radiolabeled glutamic acid ((14)C-Glu), followed by a sequential extraction allowing the quantification of the radioactivity associated to different chemical fractions, representative of different biogeochemical processes. This technique was devised to simulate the fate of simple dissolved compounds resulting from the degradation of particulate organic matter near the seafloor. In our experiment the substrate underwent both biotic (mineralization, bacterial incorporation) and abiotic (geopolymerization)...
Tipo: Text Palavras-chave: Interface eau–sédiment; Chambre benthique; Incubation in situ; Marge continentale; Méditérranée nord-occidentale; Sediment-waterinterface; Benthic chamber; In situ incubations; Continental margin; NW Mediterranean.
Ano: 2002 URL: http://archimer.ifremer.fr/doc/00322/43318/42936.pdf
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Cold-water coral habitats in the Penmarc'h and Guilvinec Canyons (Bay of Biscay): Deep-water versus shallow-water settings ArchiMer
De Mol, Lies; Van Rooij, David; Pirlet, Hans; Greinert, Jens; Frank, Norbert; Quemmerais-amice, Frederic; Henriet, Jean-pierre.
In 1948, Le Danois reported for the first time the occurrence of living cold-water coral reefs, the so-called "massifs coralliens", along the European Atlantic continental margin. In 2008, a cruise with R/V Belgica was set out to re-investigate these cold-water corals in the Penmarc'h and Guilvinec Canyons along the Gascogne margin of the Bay of Biscay. During this cruise, an area of 560 km(2) was studied using multibeam swath bathymetry, CTD casts, ROV observations and USBL-guided boxcoring. Based on the multibeam data and the ROV video imagery, two different cold-water coral reef settings were distinguished. In water depths ranging from 260 to 350 m, mini mounds up to 5 m high, covered by dead cold-water coral rubble, were observed. In between these...
Tipo: Text Palavras-chave: Bay of Biscay; Continental margin; Canyons; Cold-water corals; Lophelia; Madrepora.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00035/14632/13318.pdf
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Estimation of gas hydrate concentration from multi-component seismic data at sites on the continental margins of NW Svalbard and the Storegga region of Norway ArchiMer
Westbrook, G; Chand, S; Rossi, G; Long, C; Bunz, S; Camerlenghi, A; Carcione, J; Dean, S; Foucher, Jean-paul; Flueh, E; Gei, D; Haacke, R; Madrussani, G; Mienert, Jurgen; Minshull, T; Nouze, Herve; Peacock, S; Reston, T; Vanneste, M; Zillmer, M.
High-resolution seismic experiments, employing arrays of closely spaced, four-component ocean-bottom seismic recorders, were conducted at a site off western Svalbard and a site on the northern margin of the Storegga slide, off Norway to investigate how well seismic data can be used to determine the concentration of methane hydrate beneath the seabed. Data from P-waves and from S-waves generated by P-S conversion on reflection were inverted for P- and S-wave velocity (V-p and V-s), using 3D travel-time tomography, 2D ray-tracing inversion and 1D waveform inversion. At the NW Svalbard site, positive V-p anomalies above a sea-bottom-simulating reflector (BSR) indicate the presence of gas hydrate. A zone containing free gas up to 150-m thick, lying immediately...
Tipo: Text Palavras-chave: Continental margin; Hydrate concentration; Seismic velocity; S wave; P wave.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6122.pdf
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Hydrate dissolution as a potential mechanism for pockmark formation in the Niger delta ArchiMer
Sultan, Nabil; Marsset, Bruno; Ker, Stephan; Marsset, Tania; Voisset, Michel; Vernant, Antoine-mathieu; Bayon, Germain; Cauquil, Eric; Adamy, J.; Colliat, J. L.; Drapeau, D..
Based on acquired geophysical, geological and geotechnical data and modeling, we suggest hydrate dissolution to cause sediment collapse and pockmark formation in the Niger delta. Very high-resolution bathymetry data acquired from the Niger delta reveal the morphology of pockmarks with different shapes and sizes going from a small ring depression surrounding an irregular floor to more typical pockmarks with uniform depression. Geophysical data, in situ piezocone measurements, piezometer measurements and sediment cores demonstrate the presence of a common internal architecture of the studied pockmarks: inner sediments rich in gas hydrates surrounded by overpressured sediments. The temperature, pressure and salinity conditions of the studied area have allowed...
Tipo: Text Palavras-chave: Methane gas hydrate; Sea floor; Marine sediments; Pore pressure; Porous media; Continental margin; Clathrate hydrate; Fluid flow; Stability; Slope.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00012/12300/9092.pdf
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Multi-disciplinary investigation of fluid seepage on an unstable margin: The case of the Central Nile deep sea fan ArchiMer
Bayon, Germain; Loncke, L.; Dupre, Stephanie; Caprais, Jean-claude; Ducassou, E.; Duperron, Sebastien; Etoubleau, Joel; Foucher, Jean-paul; Fouquet, Yves; Gontharet, S.; Henderson, G. M.; Huguen, Caroline; Klaucke, I.; Mascle, J.; Migeon, S.; Olu-le-roy, Karine; Ondreas, Helene; Pierre, C.; Sibuet, Myriam; Stadnitskaia, A.; Woodside, J..
We report on a multidisciplinary study of cold seeps explored in the Central Nile deep-sea fan of the Egyptian margin. Our approach combines in situ seafloor observation, geophysics, sedimentological data, measurement of bottom-water methane anomalies, pore-water and sediment geochemistry, and Th-230/U dating of authigenic carbonates. Two areas were investigated, which correspond to different sedimentary provinces. The lower slope, at similar to 2100 m water depth, indicates deformation of sediments by gravitational processes, exhibiting slope-parallel elongated ridges and seafloor depressions. In contrast, the middle slope, at similar to 1650 m water depth, exhibits a series of debris-flow deposits not remobilized by post-depositional gravity processes....
Tipo: Text Palavras-chave: Authigenic carbonate; U Th; Cold seep; Continental margin; Nile.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6586.pdf
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Organic matter in sediments in the mangrove areas and adjacent continental margins of Brazil .1. Amino acids and hexosamines ArchiMer
Jennerjahn, Tc; Ittekkot, V.
The nature of sedimentary organic matter from mangroves and the continental margin of eastern Brazil (8 degrees-24 degrees S) has been investigated in order to obtain information on sources and diagenetic processes. The organic matter content of mangrove sediments is three to four times higher than the maximum content of continental margin sediments. Downslope distribution of organic carbon, nitrogen, amino acids and hexosamines shows an enrichment in water depths between 800 m and 1000 m. The distribution of individual amino acids and hexosamines is highly variable in sedimentary organic matter from mangroves and the continental margin, and the observed compositional differences are mainly due to diagenetic alteration. Organic matter is highly reactive in...
Tipo: Text Palavras-chave: Organic carbon; Amino acids; Carbon cycle; Mangroves; Continental margin.
Ano: 1997 URL: http://archimer.ifremer.fr/doc/00093/20403/18070.pdf
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Origin and Accumulation of Trace Elements in Sediments of the Northwestern Mediterranean Margin ArchiMer
Cossa, Daniel; Buscail, R.; Puig, P.; Chiffoleau, Jean-francois; Radakovitch, Olivier; Jeanty, G.; Heussner, S..
Continental margins receive natural and anthropogenic trace elements (TEs) from direct atmospheric deposition of aerosols onto the sea surface and from advection of riverine suspended particles and/or resuspended sediments from the continental shelf/slope. When the margin is incised by submarine canyons, as for example in the Northwestern Mediterranean Sea, most of these particles are preferentially transferred via these topographic features towards their final repositories in the abyssal plain. The Gulf of Lions (GoL) shelf receives the largest particulate riverine input to the Western Mediterranean, with its associated chemical contaminants originating from the industrialized and urbanized Rhone Valley. Sediments samples (grabs, cores and moored traps)...
Tipo: Text Palavras-chave: Trace-element; Sediment; Canyon; Continental margin; Mediterranean.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00188/29971/28424.pdf
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Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget ArchiMer
Raimonet, Melanie; Ragueneau, Olivier; Jacques, Vincent; Corvaisier, Rudolph; Moriceau, Brivaela; Khripounoff, Alexis; Pozzato, Lara; Rabouille, Christophe.
Mechanisms controlling the transfer and retention of silicon (Si) along continental margins are poorly understood, but play a major role in the functioning of coastal ecosystems and the oceanic biological pump of carbon. Deep-sea fans are well recognized as carbon sink spots, but we lack knowledge about the importance of the fans in the global Si cycle. Here, we provide a first estimate of the role played by the Congo deep-sea fan, one of the biggest in the world, in the Si cycle. Sediment cores sampled in the deep-sea fan were analyzed to build a Si mass balance. An exceptionally high accumulation rate of amorphous silica aSiO(2) (2.29 +/- 0.58 mol Si m(-2) y(-1)) was found, due to a high sedimentation rate and the presence of aluminum in the sediments....
Tipo: Text Palavras-chave: Continental margin; Land-sea export; Silica cycle; Congo canyon; Deep-sea fan.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00251/36242/35797.pdf
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The influence of geological, geochemical, and biogenic habitat heterogeneity on seep biodiversity ArchiMer
Cordes, Erik E.; Cunha, Marina R.; Galeron, Joelle; Mora, Camilo; Olu-le Roy, Karine; Sibuet, Myriam; Van Gaever, Saskia; Vanreusel, Ann; Levin, Lisa A..
Cold seeps are among the most heterogeneous of all continental margin habitats. Abiotic Sources of heterogeneity in these systems include local variability in fluid flow, geochemistry, and substrate type, which give rise to different sets of microbial communities, microbial symbiont-bearing foundation species, and associated heterotrophic species. Biogenic habitats created by microbial mats and the symbiotic species including vesicomyid clams, bathymodiolin mussels, and siboglinid tubeworms add an additional layer of complexity to seep habitats. These forms of habitat heterogeneity result in a variety of macrofaunal and meiofaunal communities that respond to changes in structural complexity, habitat geochemistry, nutrient sources, and interspecific...
Tipo: Text Palavras-chave: Beta diversity; Chemosynthetic communities; Cold seep; Continental margin; Macrofauna; Meiofauna; Metacommunity; Species accumulation.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00002/11281/7826.pdf
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Thinning of the Goban Spur continental margin and formation of early oceanic crust: Constraints from forward modelling and inversion of marine magnetic anomalies ArchiMer
Louvel, Veronique; Dyment, Jerome; Sibuet, Jean-claude.
The deep seismic reflection profile Western Approaches Margin (WAM) cuts across the Goban Spur continental margin, located southwest of Ireland. This non-volcanic margin is characterized by a few tilted blocks parallel to the margin. A volcanic sill has been emplaced on the westernmost tilted block. The shape of the eastern part of this sill is known from seismic data, but neither seismic nor gravity data allow a precise determination of the extent and shape of the volcanic body at depth. Forward modelling and inversion of magnetic data constrain the shape of this volcanic sill and the location of the ocean-continent transition. The volcanic body thickens towards the ocean, and seems to be in direct contact with the oceanic crust. In the contact zone, the...
Tipo: Text Palavras-chave: Continental margin; Goban Spur; Magnetic anomalies; Ocean-continent boundary.
Ano: 1997 URL: http://archimer.ifremer.fr/doc/00337/44777/44601.pdf
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Total mercury in the water column near the shelf edge of the European continental margin ArchiMer
Cossa, Daniel; Cotte Krief, Marie-hélène; Mason, Robert P.; Bretaudeau-sanjuan, Jane.
The purpose of this paper is to investigate the distribution and the relative importance of processes that affect mercury distribution in the water column at the shelf edge of the Celtic Sea, on the western European continental margin. The water column, down to 4500 m, was sampled during two cruises, one in winter 1994 and the other in June 1995, on eight stations. Total mercury concentrations ranged from 0.29 to 9.37 pM with the extreme values in the first 200 m. The highly variable concentrations in the surface layers are attributed to intense atmospheric-sea water exchange processes. The low concentrations encountered in the shelf water prelude any significant influence of continental waters in this area. In the mixed layer, biological uptake and...
Tipo: Text Palavras-chave: Regeneration; Atmospheric deposition; Deep profile; Upwelling; Atlantic ocean; Celtic Sea; Shelf break; Continental margin; Mercury.
Ano: 2004 URL: https://archimer.ifremer.fr/doc/2004/publication-660.pdf
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