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Registros recuperados: 13
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A joint electromagnetic and seismic study of an active pockmark within the hydrate stability field at the Vestnesa Ridge, West Svalbard margin ArchiMer
Goswami, Bedanta K.; Weitemeyer, Karen A.; Minshull, Timothy A.; Sinha, Martin C.; Westbrook, Graham; Chabert, Anne; Henstock, Timothy J.; Ker, Stephan.
We acquired coincident marine controlled-source electromagnetic (CSEM), high-resolution seismic reflection and ocean-bottom seismometer (OBS) data over an active pockmark in the crest of the southern part of the Vestnesa Ridge, to estimate fluid composition within an underlying fluid-migration chimney. Synthetic model studies suggest resistivity obtained from CSEM data can resolve gas or hydrate saturation greater than 5% within the chimney. Acoustic chimneys imaged by seismic reflection data beneath the pockmark and on the ridge flanks, were found to be associated with high-resistivity anomalies (+2-4 m). High-velocity anomalies (+0.3 km/s), within the gas hydrate stability zone (GHSZ) and low-velocity anomalies (-0.2 km/s) underlying the GHSZ, were also...
Tipo: Text Palavras-chave: Gas hydrate; Svalbard; CSEM; Saturation; Pockmark; Vestnesa.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00283/39458/37928.pdf
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Comments on the paper of Gay et al. (2006) Seafloor facies related to upward methane flux within a Giant Pockmark of the Lower Congo Basin. Marine Geology 226 : 81-95 ArchiMer
Olu, Karine.
The paper by Gay et al. describes a giant pockmark on the basis of geological and biological data collected during ROV dives. The description of seep communities based on a transect across the pockmark includes some mistakes. Part of the description of the fauna is attributed to Olu-Le Roy et al. (2003) and includes data that have not been presented in this oral communication. An "evolutive model" is proposed, based on these data and on an incorrect interpretation of symbiotic species requirements (classification of methane vs sulfide dependent species). In this note, I would like to point out the mistakes of this paper and express why their model cannot be used to describe the reality of the seabed.
Tipo: Text Palavras-chave: BIOZAIRE; ZAIANGO; Palaeochannel; Hydrates; Chemosynthesis; Seafloor facies; Fluid migration; Pockmark.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2276.pdf
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Distribution and temporal variation of mega-fauna at the Regab pockmark (Northern Congo Fan), based on a comparison of videomosaics and geographic information systems analyses ArchiMer
Marcon, Yann; Sahling, Heiko; Allais, Anne-gaelle; Bohrmann, Gerhard; Olu, Karine.
The Regab pockmark is a large cold seep area located 10 km north of the Congo deep sea channel at about 3160 m water depth. The associated ecosystem hosts abundant fauna, dominated by chemosynthetic species such as the mussel Bathymodiolus aff. boomerang, vestimentiferan tubeworm Escarpia southwardae, and vesicomyid clams Laubiericoncha chuni and Christineconcha regab. The pockmark was visited during the West African Cold Seeps (WACS) cruise with RV Pourquoi Pas? in February 2011, and a 14,000-m2 high-resolution videomosaic was constructed to map the most populated area and to describe the distribution of the dominant megafauna (mussels, tubeworms and clams). The results are compared with previous published works, which also included a videomosaic in the...
Tipo: Text Palavras-chave: Cold seep; Fauna; Mosaic; Pockmark; Regab; Temporal variation.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00144/25528/23765.pdf
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Diversité et activité des communautés microbiennes dans des sédiments marins associés aux émissions de fluides froids ArchiMer
Lazar, Cassandre Sara.
A large portion of the greenhouse gas methane on Earth is trapped in marine sediments. However, little methane actually reaches the hydrsphere and the atmosphere, because it is efficiently consumed by anaerobic methane-oxidizing Archaea (ANME). This methane is mainly biogenic in marine sédiments, and is produced by methanogenic Archaea. Methane ascends from deep sources to the seabed, in cold seep sites of continental margins. In order to study microbial community diversity in cold seeps, and to determine geochemical factors that control these microbial communities, we compared four geochemically and geologically distinct sites. In this work, molecular tools (PCR, RT-PCR, DGGE, cloning) as well as genetic markers (16S rRNA, mcrA, dsrB) were employed, to...
Tipo: Text Palavras-chave: Diversité moléculaire; Archaea; Méthanogène; ANME; McrA; DsrB; DGGE; Volcan de boue; Pockmark; Saumures; Fluides froids; Méthane; Mer de Norvège; Mer Méditerranée; Sédiments.; Molecular diversity; Archaea; Methanogen; ANME; McrA; DsrB; DGGE; Mud volcano; Pockmark; Brines; Cold seep; Methane; Norwegian Sea; Mediterranean Sea; Sediments..
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00031/14250/11534.pdf
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Etude de la dynamique des pockmarks associés à la présence d'hydrates de gaz : enseignements généraux à partir de deux cas d'école situés sur la marge africaine ArchiMer
De Prunele, Alexis.
The present work describes the dynamics of two pockmark areas, off West Africa. The intention is to propose two different approaches to study the relationships between fluid migration and pockmarks. The first investigated area corresponds to a pockmark cluster called Preowei, located off Nigeria. Geochemical analyses and modeling were combined with seismic data to detail the hydrocarbon migration pattern at this area, with implication on both the pockmark formation and the evolution of their morphology. The proposed interpretation seeks to identify the conceptual bases of pockmark evolution over time at this area. It is argued that the cluster has been active for at least 2700 years, and it is still at the stage of hydrate formation for some pockmarks and...
Tipo: Text Palavras-chave: Hydrate de gaz; Marge africaine; Hydrates; Gas hydrate; Pockmark; African margin; Hydrate.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00498/60936/64329.pdf
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Gas hydrate distributions in sediments of pockmarks from the Nigerian Margin - Results and interpretation from shallow drilling ArchiMer
Wei, Jiangong; Pape, Thomas; Sultan, Nabil; Colliat, Jean-louis; Himmler, Tobias; Ruffine, Livio; De Prunele, Alexis; Dennielou, Bernard; Garziglia, Sebastien; Marsset, Tania; Peters, Carl A.; Rabiu, Abdulkarim; Bohrmann, Gerhard.
A joint research expedition between the French IFREMER and the German MARUM was conducted in 2011 using the R/V Pourquoi pas? to study gas hydrate distributions in a pockmark field (1141 – 1199 meters below sea surface) at the continental margin of Nigeria. The sea floor drill rig MeBo of MARUM was used to recover sediments as deep as 56.74 meters below seafloor. The presence of gas hydrates in specific core sections was deduced from temperature anomalies recorded during continuous records of infrared thermal scanning and anomalies in pore water chloride concentrations. In situ sediment temperature measurements showed elevated geothermal gradients of up to 258 °C/km in the center of the so-called pockmark A which is up to 4.6 times higher than that in the...
Tipo: Text Palavras-chave: Gas hydrate; Pockmark; Chloride profile; Infrared thermal imaging; Fluid flow; Nigerian continental margin; MeBo drill rig.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00213/32382/30846.pdf
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Gas occurrence and shallow conduit systems in the Western Sea of Marmara: a review and new acoustic evidence ArchiMer
Saritas, Hakan; Cifci, Gunay; Geli, Louis; Thomas, Yannick; Marsset, Bruno; Henry, Pierre; Grall, Celine; Rochat, Alexis.
Based on 3D and 2D high-resolution multichannel seismic reflection data in the Western High-Sea of Marmara, this study reviews shallow gas occurrence and related structures and classifies gas conduit systems within the upper, few hundred meter-thick sediment layers below the seafloor. Acoustic anomalies including high amplitude-reverse polarity reflections (bright spots), low amplitude transparent zones, chaotic or discontinuous reflections, pull-down effects, and plumes in the water column are interpreted in terms of natural gas occurrence and fluid flow structures (e.g., mud volcanoes, pockmarks). The gas occurrence is thought to be mostly of thermogenic origin. Mud volcanoes are one of the primary gas conduits forming craters on the seabed due to...
Tipo: Text Palavras-chave: Shallow gas; Gas conduit systems; Mud volcano; Pockmark; 2D-3D seismic; Western High; Sea of Marmara.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00456/56737/58689.pdf
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Helium transport in sediment pore fluids of the Congo-Angola margin ArchiMer
Chaduteau, Carine; Jean-baptiste, Philippe; Fourre, Elise; Charlou, Jean-luc; Donval, Jean-pierre.
During the ZaiRov2 cruise of the ZaiAngo project (1998-2000) on the passive Congo-Angola margin, several gravity cores were analyzed for helium isotopic composition of sedimentary pore waters in two cold fluid seepage zones: the Astrid slide area and the Regab giant pockmark. Gas concentration and isotopic composition are presented along with thermal data in terms of the origin and circulation of fluids. Helium isotope data lie on a mixing line between bottom seawater and an almost pure radiogenic. Helium and temperature vertical profiles are well described by the classic diffusion-advection equation. On the basis of He profiles, we estimate the advection rate on the rim of the pockmark between 1.2 and 2.3 mm/a. The He flux derived for a pure diffusive...
Tipo: Text Palavras-chave: Zaire Angola margin; Sediment; Regab; Pore fluids; Pockmark; Helium.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6112.pdf
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Origine et circulation des fluides dans les sédiments des marges. Contribution de l'hélium et du méthane dans la compréhension des processus. Étude de 2 zones actives ArchiMer
Chaduteau, Carine.
Fluid migration is a very important process in marine sediments on margins. Studying fluids is fundamental to constrain the energy potential of margins. Methane is the predominant gas in marine sediments, deriving primarily from the degradation of organic matter. However methane could be also generated through the serpentinization of mantle rocks underlying the sedimentary cover in some specific geodynamical settings. One way to test this hypothesis is to use helium isotopes, which are known to be powerful tracers of the fluid-mantle interaction. To this purpose, a new method has been developed for the sampling and the quantitative extraction of dissolved helium from sediment pore-waters. During the Zairov2 and Vicking cruises, samples were collected in...
Tipo: Text Palavras-chave: Mantle; Serpentinization; Advection; Mud volcano; Pockmark; Methane; Helium; Fluid; Margin; Manteau; Serpentinisation; Advection; Volcan de boue; Pockmark; Méthane; Hélium; Fluide; Marge.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/these-3724.pdf
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Pockmarks on the South Aquitaine Margin continental slope: The seabed expression of past fluid circulation and former bottom currents ArchiMer
Michel, Guillaume; Dupre, Stephanie; Baltzer, Agnes; Ehrhold, Axel; Imbert, Patrice; Pitel, Mathilde; Loubrieu, Benoit; Scalabrin, Carla; Lazure, Pascal; Marie, Louis; Geldof, Jean-baptiste; Deville, Eric.
Inactive and mostly elongated pockmarks of 100–200 m in dimension were recently discovered on the South Aquitaine Margin continental slope. They are distributed at water depths greater than 350 m in both interfluve and sediment-wave areas, and are strongly controlled by the sedimentary morphology and architecture. Water column and seafloor backscatter and sub-bottom profiler data do not exhibit present-day or past gas evidence, e.g., massive and continuous gas releases at the seabed and fossil methane-derived authigenic carbonates. It is thus proposed that the pockmarks originated from a shallow source and result from relatively recent and short-duration gas or water expulsion events. Former near-bottom currents may have contributed to the elongation of...
Tipo: Text Palavras-chave: Pockmark; Fluid; Seabed morphology; Aquitaine slope; GIS; Currents.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00413/52491/53279.pdf
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ROV study of a giant pockmark on the Gabon continental margin ArchiMer
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.
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...
Tipo: Text Palavras-chave: Gabon; Microbathymetric map; ROV; Exploration; Pockmark; Equatorial African margin.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-1239.pdf
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Seafloor facies related to upward methane flux within a Giant Pockmark of the Lower Congo Basin ArchiMer
Gay, Aurelien; Lopez, M; Ondreas, Helene; Charlou, Jean-luc; Sermondadaz, G; Cochonat, Pierre.
The origin of the cold fluid venting from a Giant Pockmark within the Lower Congo Basin has been elucidated based upon results of precise mapping, submersible dives, gravity coring and isotopic analyses realized under a TOTAL-IFREMER cooperative project (ZAIANGO and BIOZAIRE projects). During four dives of the IFREMER ROV-Victor 6000, the bottom was filmed, hard and soft samples were lifted from the sediment, and water samples were collected with a CTD-rosette system. The detailed dip map shows that the 800 in wide Giant Pockmark is a composite feature due to the coalescence of multiple 100 in wide depressions that displays a broad range of biological, mineralogical and chemical features on the seafloor, leading to a seafloor anomaly recorded on the...
Tipo: Text Palavras-chave: BIOZAIRE; ZAIANGO; Palaeochannel; Hydrates; Chemosynthesis; Seafloor facies; Fluid migration; Pockmark.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1114.pdf
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Types of fluid-related features controlled by sedimentary cycles and fault network in deepwater Nigeria ArchiMer
Marsset, Tania; Ruffine, Livio; Ker, Stephan; Cauquil, E.; Gay, Aurelien.
The seismic characteristics of focused fluid-related features such as pockmarks and carbonate build-ups on the Nigerian continental slope have been investigated using complementary seismic data sets (reprocessed 3D exploration data and 2D Very High Resolution hull-mounted and near-bottom seismic data) coupled with the results of previous studies (sedimentological, geotechnical and geochemical analyses). The results show different types of fluid-related features within the hemipelagic phase of long duration (∼1 Myr) Turbidite/Hemipelagic cycles. They are the product of the disturbance of the hosting sediments following two main distinct processes: (1) no or low sediment deposition caused by fluid escape associated with seafloor settlement (benthic fauna,...
Tipo: Text Palavras-chave: Niger delta; Fluid flow; Pockmark; Gas hydrates; Methane-derived carbonate; Fault network; Sedimentary cycles.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00405/51650/52199.pdf
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