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| Registros recuperados: 64 | |
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| Bayon, Germain; Henderson, Gideon M.; Etoubleau, Joel; Caprais, Jean-claude; Ruffine, Livio; Marsset, Tania; Dennielou, Bernard; Cauquil, Eric; Voisset, Michel; Sultan, Nabil. |
| The application of uranium-thorium dating methods to authigenic carbonates provides unique constraints on the temporal evolution of methane seeps at ocean margins. In this study, we report U-Th isotope measurements for carbonate breccias collected from within a hydrate-bearing pockmark located at the Niger Delta margin. These concretions were extracted from a carbonate-rich layer in the upper two meters of a sediment core (N2-KS-44; ~ 1200 m water depth), well above the present-day sulphate-methane transition zone (about 3 m depth) and the presence of gas hydrates in the sediment. The stratigraphy of core N2-KS-44 was established by tuning its downcore Al/Ti profile to a well-dated nearby reference core, and carbonate 230Th/U ages were calculated using... |
| Tipo: Text |
Palavras-chave: Gas hydrates; Pockmarks; U-series; Authigenic carbonates; Niger delta. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00286/39708/41518.pdf |
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| Bassetti, Maria-angela; Berne, Serge; Jouet, Gwenael; Taviani, M; Dennielou, Bernard; Flores, J; Gaillot, Arnaud; Gelfort, R; Lafuerza, S; Sultan, Nabil. |
| Thick forced regressive units on the wide continental shelf of the Gulf of Lions (western Mediterranean) recorded the composite effect of sea level changes during the Quaternary. They are mostly composed of coastal siliciclastic and bioclastic wedges showing clinoform geometry. These deposits have been intensively explored through high-resolution seismic investigations, but only recently it was possible to ground truth seismic interpretations, based on a long (100 m) borehole that crossed the succession and recovered a large part of the mainly sandy deposits (similar to 84% recovery). A multiproxy analysis of the sedimentary succession shows that (1) the stratal architecture of the shelf margin is defined by major bounding surfaces that are polygenic... |
| Tipo: Text |
Palavras-chave: Paleoclimate; Mediterranean; Quaternary; Shoreface. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4929.pdf |
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| Vanneste, Maarten; Sultan, Nabil; Garziglia, Sebastien; Forsberg, Carl Fredrik; L'Heureux, Jean-sebastien. |
| In this paper, we present the current practice of investigations of seafloor instabilities and deformation processes, based on extensive research conducted over the last years, which sets the scene for future research activities in this field. The mapping of the continental margins and coastal areas with ever increasing resolution systematically reveals evidence of instabilities and deformation processes, both active and palaeo-features. In order to properly assess the hazards and risks related to these features, an integrated and multi-disciplinary approach is essential, but challenging. Such an approach consists of combining field data (geophysics, geology, sedimentology, geochemistry and geotechnical data) with numerical simulations constrained by... |
| Tipo: Text |
Palavras-chave: Marine geotechnics; Slope stability; Sediment failures; Fluid flow; Shear strength; Marine geophysics; Monitoring; Excess pore pressure; Site investigations. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00173/28378/26692.pdf |
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| Sultan, Nabil; Garziglia, Sebastien. |
| Multi-phase fluid conditions encountered in geotechnical and geo-environmental problems have led to the development of models that account for the influence of gas solubility and compressibility on the behaviour of soils of various grain sizes. Yet, no consideration has been given to damages related to the nucleation and growth of gas bubbles in fine-grained soils. The purpose of this paper is to present a Cam Clay based constitutive model extended to incorporate such detrimental effects on gassy soils. This is achieved by deriving an analytical expression relating the preconsolidation pressure to a damage parameter dependent on the gas content. That expression is coupled to a deviatoric yield surface accounting for inherent and stress-induced anisotropy.... |
| Tipo: Text |
Palavras-chave: Compressibility; Constitutive relations; Offshore engineering; Shear strength. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00245/35621/34133.pdf |
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| Bourillet, Jean-francois; Damy, Gilbert; Dussud, Loic; Sultan, Nabil; Woerther, Patrice; Migeon, Sebastien. |
| 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... |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00071/18198/15766.pdf |
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| Sultan, Nabil. |
| While it is well accepted that gas hydrate dissociation at the base of the Gas Hydrate Stability Zone (GHSZ) can generate high excess pore pressure and leads to sediment deformation, the consequence in terms of pore pressure of the dissolution of the gas hydrate at the top of the Gas Hydrate Occurrence Zone (GHOZ) remains neglected. The purpose of this comment on Xu and Germanovich [2006] article is to demonstrate that gas hydrate dissolution in the GHSZ may generate excess pore pressure and to point out the risk related to hydrate dissolution at the top of the GHOZ. |
| Tipo: Text |
Palavras-chave: Pore pressure; Hydrate; Dissolution; Dissociation. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2318.pdf |
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| Sultan, Nabil; Voisset, Michel; Marsset, Bruno; Marsset, Tania; Cauquil, E; Colliat, J. |
| The study area, offshore Nigeria, is located in one of the compressional zones within the Niger Delta, which is characterized by imbricate thrust structures. Although the low mean slope angle (around 2°), bathymetry data from the study area have shown the existence of several submarine landslides which coincide with known subsurface faulted compressive features. In this paper, we have focused on a submarine slide occurring in water depths ranging between 1690 and 1750 m. Headwall scars, internal architecture and associated deposits have been characterized using a combination of 3D seismic data, near-bottom echosounder seismic profiles, Kullenberg cores and in-situ geotechnical measurements. The slide shows horseshoe shaped headwall scars and depositional... |
| Tipo: Text |
Palavras-chave: Slope stability; Piezometer; Penetrometer; Niger Delta; Modelling; Compressional structures. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2408.pdf |
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| Sultan, Nabil; Cattaneo, Antonio; Sibuet, Jean-claude; Schneider, Jean-luc. |
| The swath bathymetric data acquired during the "Sumatra Aftershocks" cruise from the Sunda trench in the Indian Ocean to the north of the Sumatra Island imaged several scars and deposits. In situ pore pressure measurements using the Ifremer piezometer and coring demonstrate that high excess pore pressure and sediment deformation was generated by a recent event in the scar of the slope failure zone identified by J.T. Henstock and co-authors. This excess pore pressure is localized in the upper sedimentary layers and is not related to an interplate subduction process. Numerical simulations of the hydrological system that take into account the hydro-mechanical properties of the upper sediment layer show that the excess pore pressure and sediment deformations... |
| Tipo: Text |
Palavras-chave: Tsunami; Sumatra; Slope failure; Pore pressure; Earthquake. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6740.pdf |
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| Sultan, Nabil. |
| Parameters affecting gas hydrate formation include temperature, pore pressure, gas chemistry, and pore-water salinity. Any change in the equilibrium of these parameters may result in dissociation (gas-hydrate turns into free gas/water mixture) and/or dissolution (gas-hydrate becomes mixture of water and dissolved gas) of the gas hydrate. While, gas-hydrate dissociation at the base of the Gas Hydrate Occurrence Zone (GHOZ) is often considered as a major cause of sediment deformation and submarine slope failures the consequence in terms of pore pressure and sediment deformation of the dissolution of the gas hydrate at the top of the GHOZ remains neglected. In this study, we quantify and compare the excess pore pressure resulting from gas hydrate dissociation... |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00226/33763/32173.pdf |
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| 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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| Bayon, Germain; Pierre, C; Etoubleau, Joel; Voisset, Michel; Cauquil, E; Marsset, Tania; Sultan, Nabil; Le Drezen, Eliane; Fouquet, Yves. |
| We report on a reconnaissance analysis of the geochemical composition of authigenic carbonates and sediment samples collected from various seepage sites on the Niger deep-sea fan. Our aim has been to investigate whether evidence for the presence of authigenic carbonates and gas hydrates within sediments is discernible from solid-phase sediment geochemistry. We show that sedimentary Sr/Ca and Mg/Ca ratios can be used to infer the presence of authigenic aragonite (Sr-rich) and Mg-rich carbonate phases (high-Mg calcite, dolomite) in cold seep settings. Using Sr/Ca and Mg/Ca ratios, the proportion (wt.%) of authigenic carbonates in Niger Fan sediments can be calculated from a mixing model between sediment fractions of terrigenous material, biogenic calcite,... |
| Tipo: Text |
Palavras-chave: Niger Delta; Gas hydrates; Cold seeps; Mg/Ca; Sr/Ca; Authigenic carbonates. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2696.pdf |
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| Dennielou, Bernard; Jallet, Laurent; Sultan, Nabil; Jouet, Gwenael; Giresse, Pierre; Voisset, Michel; Berne, Serge. |
| Emplacement of post-glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity. On the continental rise of the Gulf of Lions (Western Mediterranean), an aseismic area, we identified turbiditic beds deposited during the rising stage and highstand of sea level. Swath bathymetry, sediment cores, in situ Cone Penetrating Tests (CPTU), heavy mineral associations and radiocarbon dating determined the source, composition, distribution and age of the turbiditic beds. Turbidites are composed of homogeneous to positively graded silts to medium sand with quartz (up to 90%), shell debris and shelfal benthic faunas. Their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms. Their source is... |
| Tipo: Text |
Palavras-chave: Holocene; Late Pleistocene; Sea level; Turbidites; Sand; Outer shelf; Canyons. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6316.pdf |
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| Lafuerza, S.; Frigola, J.; Canals, M.; Jouet, Gwenael; Bassetti, Maria-angela; Sultan, Nabil; Berne, Serge. |
| We show the results provided by piezocone tests in determining the stratigraphic profile and the soil classification of two drilling sites in the outer shelf and the upper slope of the Gulf of Lion, PRGL2 and PRGL1, respectively. Correlations with grain-size data indicate that sleeve friction can be used for profiling fine-grained sediments (site PRGL1), whereas cone tip resistance is the most adequate for sequences made of alternations of coarse- and fine-grained intervals (site PRGL2). Normalized cone resistance and friction ratio proved to be also appropriate for soil stratigraphy as it depicts trends in the coarse fraction of the tested soil. Silts and clays present in similar proportions at site PRGL1 responded to piezocone testing as pure clays... |
| Tipo: Text |
Palavras-chave: Gulf of Lion; Soil classification; Stratigraphy; Piezocone. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6121.pdf |
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| Garziglia, Sebastien; Sultan, Nabil; Cattaneo, Antonio; Ker, Stephan; Marsset, Bruno; Riboulot, Vincent; Voisset, Michel; Adamy, J.; Unterseh,. |
| In a site investigation of the eastern part of the offshore Niger delta, cone penetration tests (CPTU) showed significant drops in tip resistance, associated with decreases in sleeve friction and induced excess pore pressures at the interface between superficial sediments and the underlying deposits of a mass-transport complex (MTC) called NG1. Such signature characteristics of weakened zones are clearly expressed at three sites where the drop in tip resistance reaches more than 40% over 2-3 m-thick intervals. Correlations between CPTU profiles and both 3D and ultrahigh-resolution 2D seismic data suggest that the weakened zones surround syndepositional the within the frontal part of NG1. Hence, weakening appears associated with the remobilization of thrust... |
| Tipo: Text |
Palavras-chave: Cone penetration tests; Shear zone; 3D seismic data; Ultrahigh-resolution 2D seismic; Mass-transport complex; Slope stability. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00105/21662/19695.pdf |
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| Pape, Thomas; Ruffine, Livio; Hong, Wei‐li; Sultan, Nabil; Riboulot, Vincent; Peters, Carl A.; Kölling, Martin; Zabel, Matthias; Garziglia, Sebastien; Bohrmann, Gerhard. |
| The evolution of submarine pockmarks is often related to the ascent of fluid from the subsurface. For pockmarks located within the gas hydrate stability zone, methane oversaturation can result in the formation of gas hydrates in the sediment. A ca. 600 m‐wide sea floor depression in deep‐waters offshore Nigeria, Pockmark A, was investigated for distributions and quantities of shallow gas hydrates, origins of hydrocarbons and time elapsed since the last major fluid ascent event. For the first time, pressure coring of shallow sediments and drilling of more than 50‐m‐long cores with the sea floor drill rig MARUM‐MeBo70 were conducted in this pockmark. Unusually high hydrate saturations of up to 51% of pore volume in the uppermost 2.5 meters of sediment in the... |
| Tipo: Text |
Palavras-chave: Pockmark; Gas hydrate; Methane; MeBo; Pressure coring; Pore water modeling. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75491/76344.pdf |
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| Marsset, Bruno; Menut, Eric; Ker, Stephan; Thomas, Yannick; Regnault, Jean-pierre; Leon, Pierre; Martinossi, Henri; Artzner, Laurent; Chenot, Damien; Dentrecolas, Stephane; Spychalski, B.; Mellier, G.; Sultan, Nabil. |
| High Resolution (220–1050 Hz) seismic acquisition performed in deep water using deep-towed systems provides unrivalled lateral resolution when compared to conventional surface seismic. The lateral resolution of these acquisitions is controlled by the width of the first Fresnel zone, taking advantage of their positions close to the sea bottom. No current existing deep towed equipment can benefit from seismic imaging processing techniques to improve this resolution as a consequence of positioning inaccuracies. The technological developments of a digital deep-towed multichannel streamer are presented with a particular attention to positioning: each hydrophone incorporates a pitch, roll and heading sensor in order to monitor the constant deformation of the... |
| Tipo: Text |
Palavras-chave: Deep-towed seismics; Multichannel streamer; Seismic imaging. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00206/31745/35690.pdf |
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| Sultan, Nabil; Cochonat, Pierre; Canals, M; Cattaneo, Antonio; Dennielou, Bernard; Haflidason, H; Laberg, J; Long, D; Mienert, J; Trincardi, F; Urgeles, R; Vorren, T; Wilson, C. |
| The Costa target areas exhibit the variability of slope instabilities needed to improve our understanding of sediment physical and mechanical properties in areas prone to sliding. That is why in this project, we have analysed the different slope failures events from different parts of the Costa target areas, which reflect diverse triggering mechanisms. The aim of the first part of this study was to identify the geotechnical response of the sediment to different external mechanisms (earthquake, rapid sedimentation and gas hydrate melting). We have focused on the relation between external mechanisms and the consequence change in the in-situ stress state and the physical, mechanical, and elastic properties of the sediment. In the second part of the paper, the... |
| Tipo: Text |
Palavras-chave: Slope instability; Sensitivity; Sedimentation; Hydrate; Earthquake. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-700.pdf |
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| Dan, Gabriela; Sultan, Nabil; Savoye, Bruno; Deverchere, Jacques; Yelles, Karim. |
| The Algerian margin is a seismically active region, where during the last century, several large magnitude earthquakes took place. This study combines geotechnical and sedimentological data with numerical modelling to quantitatively assess the present-day slope stability of the Algerian margin. Geotechnical laboratory tests, such as cyclic triaxial tests, oedometric tests and vane shear tests were carried out on sediment cores collected on the study area. The liquefaction potential of a sediment column located about 30 km from the BoumerdSs earthquake epicentre of 21st May 2003 was evaluated theoretically for an earthquake of M (w) = 6.8. We show that thin sand and silt beds such as those described on recovered sediment cores are the main cause of sediment... |
| Tipo: Text |
Palavras-chave: Earthquakes; Potential of liquefaction; Slope stability; Algerian margin. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6448.pdf |
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| Registros recuperados: 64 | |
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