Mechanisms of Sedimentary Dispersal on the Nile Deep Sea Fan

By

Lies Loncke¹, Gilbert Bellaiche¹, Laurence Droz², Jean Mascle³

(1) Géosciences Azur, 06235 Villefranche-sur-mer, France (2) CNRS, 29280 Plouzané, France (3) Geosciences Azur, 06235 Villefranche-sur-Mer, France

 Depending on the areas, dominant sedimentary dispersal mechanisms can be observed on the Nile deep-sea fan:

- In a western province, a single feeder canyon, and related ramified channel-levee system ending by large sandy lobes (well identified on backscatter data and sampled by coring) guide turbiditic flows directly into the abyssal plain. Avulsions are frequent; and huge slope destabilizations have led to westward migration of successive main active channels.

- In a central province, mass wasting processes seem to prevail, at least in recent times: Eastwards, active salt tectonics interrupt channels, and prevent from any steady channel-levee development. Westwards, sediment waves are observed over large surfaces. The presence, within this field, of a few channels, as well as of minor chaotic block rotations and discontinuities, suggest interactions between turbidity currents and creeping processes to form sediment waves.

- In an eastern province cross-cut by a wide NW-SE tectonic corridor, disrupted channels are frequently observed, and echo-character analysis evidences the importance of mass wasting deposits nearby the main tectonic features. Successive channel activities and disruptions, as well as the presence of sandy ponded basins, suggest significant trapping of turbiditic deposits within the tectonized belt.

- In a levantine area, a single sinuous channel, likely originating from the Sinai Peninsula, is observed on nearly 200 km. To the north, it merges with levantine channels. This composite system constitutes a path allowing turbiditic deposition south of Cyprus.

- Finally, upslope the eastern provinces, sedimentary dunes, probably generated by easterly longshore currents, have been identified.