Widespread active seepage activity on the Nile Deep Sea Fan (offshore Egypt) revealed by high-definition geophysical imagery.

Dupré, Stéphanie, Woodside, John, Klaucke, Ingo , Mascle, Jean and Foucher, Jean-Paul (2010) Widespread active seepage activity on the Nile Deep Sea Fan (offshore Egypt) revealed by high-definition geophysical imagery. Marine Geology, 275 . pp. 1-19. DOI 10.1016/j.margeo.2010.04.003.

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Abstract

Fluid escape structures on the Nile Deep Sea Fan were investigated during the MEDIFLUX MIMES expedition in 2004. Mud volcanoes, pockmarks and authigenic carbonate structures were surveyed for the first time with a high-resolution deep-towed 75 kHz sidescan sonar and a 2–8 kHz Chirp sediment echosounder. In combination with existing multibeam bathymetry and detailed seafloor in situ geological observations, these new data allowed detailed seep analyses. About 60 gas flares were detected acoustically in the water column from the sidescan sonar raw data atwater depths from 770 to 1700 m. These gas flares coincide at the seabed with 1) the centres of the mud volcanoes where mud is also extruded, 2) the borders of the mud volcanoes where the emitted gases contribute to the precipitation of authigenic carbonates, and 3) to the edges of broad sheets of authigenic carbonates. Subsurface sediments are commonly disturbed by ascending fluids throughout the delta, with an abundance of seep-related carbonate structures on the seafloor. The feeder channels below mud volcanoes, similar to the gas conduits below the widespread carbonate crust structures and pockmarks, are relatively narrow and, for the vast majority of them, do not exceed a few metres in diameter. The seeps on the Nile Deep Sea Fan clearly follow lineations on the seafloor that ee can relate to faults.

Document Type: Article
Keywords: Volcanology; Geophysics; Geochemistry; Nile Deep Sea Fan, seepage, backscatter, cold seep, sidescan sonar, mud volcano, high-resoulution, gas chimneys, authigenic carbonates
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.margeo.2010.04.003
ISSN: 0025-3227
Projects: MIMES, MEDIFLUX, EUROMARGINS
Date Deposited: 02 Sep 2010 14:15
Last Modified: 08 Aug 2017 09:36
URI: http://oceanrep.geomar.de/id/eprint/8853

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