Recent depositional patterns of the Nile deep-sea fan from echo-character mapping

Abstract

The Nile deep-sea fan was surveyed in 1998 using swath multibeam bathymetry, backscatter imagery, and 3.5 kHz and seismic profiling. On the basis of this new data set, the fan has been divided into three main provinces: western, central, and eastern. Recent sedimentary patterns, as deduced from echo-character mapping, show that gravity-induced sedimentary deposits are predominant and are expressed through either slides, debris flows, or turbidites. Turbidity processes are particularly active in the westernmost province through a well-developed network of deep-sea channels. This network controls turbiditic flows that, subsequently, overflow levees. Mass-wasting processes are extremely efficient all over the Nile deep-sea fan. In the upper central province, a broad allochthonous tongue of mass-flow deposits, generated by slope destabilizations, may have led to channel avulsions and migrations. In the eastern province, a northwest-southeast deformed belt resulting from combined deep-seated and salt-related tectonics contains large proportions of destabilized sediments (i.e., originating from destabilization processes such as mass movements), probably settled by recent tectonic activity. This article highlights (1) the influence of both thin-skinned and thick-skinned tectonics on sedimentary distribution, and (2) the predominance of gravity-induced sediments (turbidites, slides, and mass flows). In such submarine fans, the distribution of debris flows and sedimentary deposits settled by turbidity currents appears fundamental in predicting reservoir geometry and economic potential.