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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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Kallel, N; Paterne, M; Duplessy, Jc; Vergnaudgrazzini, C; Pujol, C; Labeyrie, L; Arnold, M; Fontugne, M; Pierre, C. |
Sea-surface temperature (SST) estimates for the last 10,000 years have been derived from foraminiferal fauna variations in ten cores from the Mediterranean Sea. For the eastern cores, modern analogs of fossil assemblages are found in the eastern Mediterranean Sea. In the Alboran and Tyrrhenian Seas, the bet analogs originate from modern fauna located either in the western Mediterranean Sea or in the North Atlantic Ocean. During the last sapropel event, centred at about 8,000 years B.P., SSTs were similar to present in the eastern basin, whereas they were colder than today by about 1.5 degrees C in the Alboran Sea and 2.5 degrees C in the Tyrrhenian Sea. Oxygen isotope measurements agree with ecological studies to show that Globigerina bulloides and... |
Tipo: Text |
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Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00093/20427/18094.pdf |
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Laubelenfant, E; Pierre, C. |
The transect from East to West Pacific realized along the equator during the Alize 2 cruise (January-March 1991) offers a unique opportunity to evaluate the effect of the equatorial upwelling on the partial derivative(13)C values of Sigma CO2 in oceanic waters. The surface partial derivative(13)C distribution from 95 degrees W to 165 degrees E is characterized by a general increase from 0.90 to 1.54 parts per thousand which parallels the temperature rise from 23 to 30 degrees C, both giving a signature of the upwelling and of the westward advection of superficial waters: the C-13 depletion in the Sigma CO2 marks the progressive influence of upwelled waters which are rich in C-13-depleted CO2 generated by organic matter remineralization. The vertical... |
Tipo: Text |
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Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00099/21016/18642.pdf |
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Dupre, Stephanie; Woodside, J; Foucher, Jean-paul; De Lange, G; Mascle, J; Boetius, A; Mastalerz, V; Stadnitskaia, A; Ondreas, Helene; Huguen, C; Harmegnies, Francois; Gontharet, Swanne; Loncke, L; Deville, E; Niemann, H; Omoregie, E; Olu, Karine; Fiala Medioni, A; Dahlmann, A; Caprais, Jean-claude; Prinzhofer, A; Sibuet, Myriam; Pierre, C; Damste, J. |
Four mud volcanoes of several kilometres diameter named Amon, Osiris, Isis, and North Alex and located above gas chimneys on the Central Nile Deep Sea Fan, were investigated for the first time with the submersible Nautile. One of the objectives was to characterize the seafloor morphology and the seepage activity across the mud volcanoes. The seepage activity was dominated by emissions of methane and heavier hydrocarbons associated with a major thermal contribution. The most active parts of the mud volcanoes were highly gas-saturated (methane concentrations in the water and in the sediments, respectively, of several hundreds of nmol/L and several mmol/L of wet sediment) and associated with significantly high thermal gradients (at 10 m below the seafloor,... |
Tipo: Text |
Palavras-chave: Seafloor morphology; Methane; Authigenic carbonate precipitation; Gas chimneys; Mud breccia; Mud volcanoes; Fluid seepage; Nile fan. |
Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-4455.pdf |
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Bertrand, P; Pedersen, Tf; Schneider, R; Shimmield, G; Lallier-verges, E; Disnar, Jr; Massias, D; Villanueva, J; Tribovillard, N; Huc, Ay; Giraud, X; Pierre, C; Venec-peyre, Mt. |
Sediments on the Namibian Margin in the SE Atlantic between water depths of similar to1000 and similar to3600 m are highly enriched in hydrocarbon-prone organic matter. Such sedimentation has occurred for more than 2 million years and is geographically distributed over hundreds of kilometers along the margin, so that the sediments of this region contain a huge concentrated stock of organic carbon. It is shown here that most of the variability in organic content is due to relative dilution by buried carbonates. This reflects both export productivity and diagenetic dissolution, not differences in either water column or bottom water anoxia and related enhanced preservation of organic matter. These observations offer a new mechanism for the formation of... |
Tipo: Text |
Palavras-chave: Petroleum source rocks; Coastal upwelling; Deep-sea sediments; Quaternary climate; Southwestern African Margin. |
Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00224/33553/31977.pdf |
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