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Seafloor geological studies above active gas chimneys off Egypt (Central Nile Deep Sea Fan)

Dupré, S. and Woodside, J. and Foucher, J. -P. and de Lange, G. and Mascle, J. and Boetius, A. and Mastalerz, V. and Stadnitskaia, A. and Ondréas, H. and Huguen, C. and Harmégnies, F. and Gontharet, S. and Loncke, L. and Deville, E. and Niemann, H. and Omoregie, E. and Olu-Le Roy, K. and Fiala-Medioni, A. and Dählmann, A. and Caprais, J. -C. and Prinzhofer, A. and Sibuet, M. and Pierre, C. and Sinninghe Damsté, J. and the Nautinil Scientific Party, . (2007) Seafloor geological studies above active gas chimneys off Egypt (Central Nile Deep Sea Fan). Deep-sea research. Part 1, Oceanographic research papers, Vol. 54, H. 7. pp. 1146-1172.

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Official URL: http://edoc.unibas.ch/dok/A5250587

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Abstract

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, the recorded temperatures reached more than 40 °C). Patches of highly reduced blackish sediments, mats of sulphide-oxidizing bacteria, and precipitates of authigenic carbonate were detected, indicative of anaerobic methane consumption. The chemosynthetic fauna was, however, not very abundant, inhibited most likely by the high and vigorous fluxes, and was associated mainly with carbonate-crust-covered seafloor encountered on the southwestern flank of Amon. Mud expulsions are not very common at present and were found limited to the most active emission centres of two mud volcanoes, where slow extrusion of mud occurs. Each of the mud volcanoes is fed principally by a main narrow channel located below the most elevated areas, most commonly in the centres of the structures. The distribution, shape, and seafloor morphology of the mud volcanoes and associated seeps over the Central Nile Deep Sea Fan are clearly tectonically controlled.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Umweltgeowissenschaften > Geochemie Stoffkreisläufe (Lehmann)
UniBasel Contributors:Niemann, Helge
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Elsevier Science
ISSN:0967-0637
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:31
Deposited On:22 Mar 2012 14:18

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