||Dupre Stéphanie, Woodside John, Klaucke Ingo, Mascle Jean, Foucher Jean-Paul
||Fluid seepages / mud volcanism in the Mediterranean and adjacent domains. 19-22 October 2005, Bologna (Italy)
||CIESM, 2006. Fluid seepages / mud volcanism in the Mediterranean and adjacent domains. CIESM Workshop Monographs, n°29, ISSN 1726-5886 pp.65-71
||free gas emission, backscatter, authigenic carbonate crust, mud volcanism, gas chimneys, Nile Deep Sea Fan
||The Nile deep sea fan system presents a rich variety of fluid escape structures, gas chimneys, pockmarks and carbonate crust mounds, brines pools, and several types of mud volcano. These seep-related structures were explored for the first time with the Nautile submersible during the 2003 Nautinil expedition and are characterized by high thermal gradients and highly gas-saturated sediments. More recently, high resolution side scan sonar data acquired during the 2004 Mimes expedition brings more detail to the geophysical imagery. The EdgeTech DTS-1 deep tow sonar coupled with a 2-8 kHz chirp subbottom penetrator was deployed around 100 m above the seafloor and operated at a frequency of 75 kHz. Several gas plumes were acoustically detected in the water column of the side scan record both in the Eastern and Central Provinces, e.g. above Isis and Amon mud volcanoes and numerous pockmarks. These observations confirm the intensity of the present-day activity offshore Egypt in terms of seepage associated with gas emissions and its continuity through time. The geophysical signature of these active sites commonly associated with high backscatter, presents, however some variability in the signal depending on the intensity and the type of seep-related structures, e.g. the presence of relatively young mud breccia or authigenic carbonate crust pavements. Acoustic mosaics of the seafloor and chirp profiles reveal subsurface sediments commonly disturbed by ascending fluids throughout the delta and usually marked by seafloor carbonate crust structures. In the Eastern Province, the wide gas chimneys, formed during successive episodes of mud extrusion associated with relatively low volume of mud breccia, are systematically associated with carbonate crust formation. The feeder channels of these mud volcanoes, similar to the gas conduits below carbonate crust structures identified over the entire delta, are relatively narrow and, for the vast majority of them, do not exceed a few tens of metres in diameter. These seep-related structures, gas chimneys and carbonate crust structures are controlled by the local and regional tectonics in connection with a complex fault network, deeply rooted faults, and shallower ones associated with salt tectonics for instance.