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Abstract

AAPG Bulletin, V. 86, No. 7 (July 2002),Copyright ©2002. The American Association of Petroleum Geologists. All rights reserved.

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

L. Loncke,1 V. Gaullier,2 G. Bellaiche,3 J. Mascle4

1Geosciences-Azur/UMR 6526, B.P. 48, 06235 Villefranche-sur-mer, France; email: [email protected]
2Laboratoire de Sedimentologie Marine, Universite de Perpignan, 52, avenue de Villeneuve, 66860 Perpignan, France; email: [email protected]
3Geosciences-Azur/UMR 6526, B.P. 48, 06235 Villefranche-sur-mer, France; email: [email protected]
4Geosciences-Azur/UMR 6526, B.P. 48, 06235 Villefranche-sur-mer, France; email: [email protected]

AUTHORS

Lies Loncke received her bachelor's and master's degrees from the universities of Bordeaux and Grenoble. She is currently a Ph.D. student at Geosciences Azur (University of Paris 6) and has participated in research surveys in the eastern Mediterranean. Her research focuses on sediment dispersion, fluid escape (gas, undercompacted muds), and thick-skinned and salt-related thin-skinned tectonics in the Nile deep-sea fan.

Virginie Gaullier received a Ph.D. from University of Paris 6 in 1993 and is an assistant professor with the Laboratory of Marine Sedimentology at the University of Perpignan, France. Her current research work uses geophysical data and analog modeling to analyze the interaction between sedimentation and gravity-driven deformation in deep-sea fans, especially salt tectonics and mass-wasting processes.

Gilbert Bellaiche is a research director for the Centre National de Recherche Scientifique (CNRS). He is a graduate of Paris University, where he studied geology and oceanography. He is a specialist in submarine canyons and deep-sea fans, which he explored in the Mediterranean Sea and around the world using several methods, including multibeam sounding systems, seismic profiling, coring, and submarine diving.

Jean Mascle holds a doctorate in science and is senior scientist at CNRS. Working in Villefranche/Mer, he is an expert on the continental margin; he has conducted many surveys (including two Ocean Drilling Project legs) on structures and sedimentary processes in different margin settings. He has published more than 150 articles and, in 2001, participated in the AAPG Distinguished Lectures Program.

ACKNOWLEDGMENTS

We are grateful to our colleagues from the PRISMED II cruise: J. Benkhelil, G. Buffet, L. Droz, M. Ergun, C. Huguen, A. Kopf, R. Levy, A. Limonov, Y. Mart, Y. Shaked, A. Volkonskaia, and J. Woodside. We wish to acknowledge the crew and the technical team of the R/V l'Atalante. We thank L. Boniface and A. Muriel for a preliminary analysis of this data set. We also thank T. Dunn, W. DeMis, and J. Lorenz for the useful comments and reviews that strengthened this article. This article is contribution 396 of Geosciences-Azur (UMR-CNRS 6526).

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.

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