High-resolution mapping of large gas emitting mud volcanoes on the Egyptian continental margin (Nile Deep Sea Fan) by AUV surveys

Abstract

Two highly active mud volcanoes located in 990-1,265 m water depths were mapped on the northern Egyptian continental slope during the BIONIL expedition of R/V Meteor in October 2006. High-resolution swath bathymetry and backscatter imagery were acquired with an autonomous underwater vehicle (AUV)-mounted multibeam echosounder, operating at a frequency of 200 kHz. Data allowed for the construction of *1 m pixel bathymetry and backscatter maps. The newly produced maps provide details of the seabed morphology and texture, and insights into the formation of the two mud volcanoes. They also contain key indicators on the distribution of seepage and its tectonic control. The acquisition of highresolution seafloor bathymetry and acoustic imagery maps with an AUV-mounted multibeam echosounder fills the gap in spatial scale between conventional multibeam data collected from a surface vessel and in situ video observations made from a manned submersible or a remotely operating vehicle.

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

“…The time difference between the establishment of one centre and another implied by this migration is additionally supported by thermal measurements (Feseker et al, 2009) and gas concentrations (Mastalerz et al, 2004;de Lange et al, 2006;Mastalerz et al, 2007). Our sidescan sonar maps reveal ridges and depressions arranged concentrically around a mud extrusion site, similar to what is exhibited in the more recent high-resolution AUV(Autonomous Underwater Vehicle)-acquired bathymetry data (Amon and Isis mud volcanoes, Dupré et al, 2008). In this view, interfingering of a series of ridges and depressions would be indicative of several successive and distinct mud extrusion pulses.…”

“…Geological structures that host seeps range from large fluid-rich "gas chimneys" to pockmarks and carbonate pavements, and fields of smaller mud volcanoes associated sometimes with brines ( Fig. 1) (Loncke et al, 2004;Dupré et al, 2007Dupré et al, , 2008Bayon et al, 2009b;Huguen et al, 2009). This paper presents detailed near bottom acoustic characterisation of mud volcanoes (Fig.…”

“…The seafloor has a variable topography with much rougher seafloor composed of ridges and valleys at the eruption sites and a smoother (older) seafloor at larger radial distances unless the surface is broken by a secondary seeping site (e.g. mud dome, authigenic carbonates) (Dupré et al, 2007;Gontharet et al, 2007;Dupré et al, 2008). Mud volcanoes associated with gas chimneys on the Nile Deep Sea Fan are not as large as other mud volcanoes in terms of volume of Sardou and Mascle (2003).…”

Niche differentiation among mat-forming, sulfide-oxidizing bacteria at cold seeps of the Nile Deep Sea Fan (Eastern Mediterranean Sea)

“…Push core samples and measurements taken in this area are marked as yellow triangle (‘ Beggiatoa ’, large filamentous bacteria), green triangle (‘ Thiomargarita ’), or white triangle (‘Reference’). The bathymetric maps were kindly provided by the Ifremer/Géoazur (France) with data recorded during the BIONIL expedition 2006 (B) or modified from Dupré et al. (2008) (C).…”

Tectonic control on the distribution of onshore mud volcanoes in parts of the Upper Benue Trough, northeastern Nigeria.

“…On passive margins mud volcanoes were documented on huge deltaic systems, e.g. on the northern slope of the Nile Deep Sea Fan (Dupré et al 2008), and in hydrocarbon-rich areas within sedimentary basins, such as in the Caspian Sea region (Planke et al 2003;Davies and Stewart 2005).…”