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| Riboulot, Vincent; Cattaneo, Antonio; Sultan, Nabil; Garziglia, Sebastien; Ker, Stephan; Imbert, Patrice; Voisset, Michel. |
| A series of pockmarks observed at the seabed matches well the perimeter of a large submarine landslide, called NG1, located on the outer shelf and continental slope of the Eastern Gulf of Guinea. NG1 extends over 200 km2, is covered by a 120-m thick sedimentary layer which tapers downslope, and has an internal structure clearly identified in 3D seismic data consisting of three adjacent units on the upper continental slope. The pockmarks above NG1 have a diameter of several tens of meters and reveal distinct origins: (1) linked to >500 m deep fluid reservoirs, (2) rooted in NG1 internal discontinuities between NG1 units, and (3) well above NG1, superficially rooted in a regional conformity (D40), which marks the lowest sea level of the Marine Isotope... |
| Tipo: Text |
Palavras-chave: Pockmarks; Fluid seepage; Submarine landslide; Sea-level changes; Piezocone; Niger Delta. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00159/27031/31906.pdf |
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| Chima, Kelvin I.; Do Couto, Damien; Leroux, Estelle; Gardin, Silvia; Hoggmascall, Nick; Rabineau, Marina; Granjeon, Didier; Gorini, Christian. |
| Located on a divergent margin dominated by gravity tectonics above overpressured marine shales, the Niger Delta slope has been described as having a stepped profile characterized by ‘filled ponded basins’ that are prone to erosion and sediment bypass. Previous studies based on 3D seismic data have described the depositional architecture of the western Niger Delta's upper slope, but calibration of the seismic facies is lacking and the timing of major changes in sedimentary record remains elusive. In this study, seismic sequence-stratigraphy, 3D geomorphological analyses of high-resolution 3D seismic data, and bio/chronostratigraphic analyses from four boreholes, enabled the identification and characterization of the depositional architecture in Neogene... |
| Tipo: Text |
Palavras-chave: West Africa; Niger Delta; Seismic sequence stratigraphy; Filled ponded basins; Mass-transport deposits; Turbidite systems; Chronostratigraphy. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00503/61492/65302.pdf |
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| Riboulot, Vincent; Sultan, Nabil; Imbert, P.; Ker, Stephan. |
| A review of recent literature shows that two geomorphologically different types of pockmarks, contribute to gas seepage at the seafloor. Type-1 pockmarks are defined as seafloor craters associated to fluid seepage and are the most classical type referred to as “pockmarks” in the literature. In contrast, Type-2 pockmarks reveal a complex seafloor morphology that may result from the formation/decomposition of gas hydrates in underlying sedimentary layers. Interpretation of very-high-resolution seismic data, sedimentological analyses and geotechnical measurements acquired from the Eastern Niger Submarine Delta reveal that Type-2 pockmarks are associated to the presence at depth of a conical body of massive gas hydrates. Based on acquired data, theoretical... |
| Tipo: Text |
Palavras-chave: Pockmarks; Gas hydrates; VHR seismic data; Piezocone; Numerical modelling; Niger Delta. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00301/41215/40643.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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| 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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| Luiselli, Luca. |
| Three species of hinge-back tortoises ( (Kinixys belliana nogueyi, Kinixys erosa, Kinixys homeana) are found in simpatry in the rainforests of the Niger Delta, southern Nigeria (west Africa). The seasonal activity patterns and food habits of these tortoises are studied in the present paper. K. erosa and K. homeana have similar activity patterns, with peaks occurring during the wet season. Kinixys belliana was found only during the wet months. There was no evidence of any specific effect of humidity of the air on their activity intensity, and it seems likely that, more than absolute values of air humidity, the crucial factor to force tortoises into high activity is the sudden change between dry days and very wet days at the onset of the rainy season (end of... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Tortoises; Kinixys belliana nogueyi; Kinixys erosa; Kinixys homeana; Food niche; Niger Delta; Nigeria. |
| Ano: 2003 |
URL: http://www.repository.naturalis.nl/record/534368 |
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