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Recently acquired Parasound and high resolution multi-channel seismic reflection data have afforded a more detailed investigation of the Mauritania Slide Complex. The slide is more complex than previously reported, and has affected an area in the order of 34,000 km 2 between~600 and > 3,500 m water depths. The ovate-shaped slide displays a long run-out distance > 300 km. Slide formation was pre-conditioned mainly by uninterrupted deposition of upwelling-induced organic-rich sediment in an open slope environment which gave rise to rapid accumulation of poorly consolidated bedded sediment intercalated with thin weak layers. The stages of slide development were characterised by multiple failure events probably occurring mainly as retrogressive sliding which exploited widespread weak layers as glide planes. The study suggests excess pore pressures as being the most important trigger mechanism for slide formation. Earthquakes associated with nearby Cape Verde Islands may have played a mostly complementary or, at one time, a leading role in triggering sediment failures. Diapiric growths have locally triggered minor instability events which resulted in remobilizing of preexisting debris flows as well as translational sliding. The combined activities of all these triggering factors are the most like cause of the complex morphology of the Mauritania Slide Complex.

Intensive research over the past decades has greatly improved our understanding of processes operating in the deep ocean. There has been a particular focus on continental margins, as sediments deposited in these areas can provide a high‐resolution record of past climatic changes, as well as serve to host some of the world's major hydrocarbon reservoirs. However, the exploration and understanding of the deep ocean remains one of the great challenges of the 21st century [Stow and Mayall, 2000], and many fascinating features still wait to be found. The potential for new deep‐water discoveries was recently highlighted during Meteor cruise M58/1 (depart Dakar, Senegal, 21 April 2003, return Las Palmas, Spain, 12 May 2003) of the Research Center Ocean Margins at the Universität Bremen in Germany. A spectacular 400‐km‐long submarine meandering channel system was discovered off Mauritania. In this article, the system is called the Cap Timiris Canyon (Figure 1). Although a series of incisional gullies at the shelf break and uppermost slope have been described before [e.g., Rust and Wienecke, 1973], the enormous size and complex morphology of this submarine channel system were previously unknown.