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A large turbidity current was detected in the Zaire submarine valley at 4000 m water depth. Current meters, turbidimeter and sediment trap deployed on a mooring located in the channel axis, although they were damaged, recorded the signature of a very high energy event. An average velocity of more than 121 cm s−1 was measured 150 m above the channel floor. Coarse sand and plant debris were collected at 40 m height. The turbidity current clearly overflowed the edges of the valley as demonstrated by the large quantity of turbiditic material (464 mg organic carbon m−2 d−1) found in the sediment trap moored 13 km south from the channel axis.

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As part of the multidisciplinary programme BIOZAIRE devoted to studying deep-sea benthic ecosystems in the Gulf of Guinea, particulate input and its relationship with near-bottom hydrodynamics were monitored using long-term moorings from 2000 to early 2005. Particular attention was given to material input through the Congo (ex-Zaïre) submarine channel that extends 760 km from the Congo River mouth to the abyssal plain (>5100 m) near 6°S. Due to its direct connection to the Congo River, the Congo canyon and channel system are characterised by particularly active recent sediment transport. During this first in situ long-term monitoring along the channel, an energetic turbidity event was observed in January 2004 at three locations along the channel from 3420 to 4790 m in depth. This event tilted and displaced the moorings installed at 3420 m (site ZR′) and 4070 m (site ZD′), and resulted in high sediment deposition at all three mooring sites. The event moved at an average velocity of 3.5 m s −1 along the numerous channel meanders between 3420 and 4070 m, then at 0.7 m s −1 between 4070 m and the end of the channel at 4790 m. The particle cloud rose above the top of the valley at 4070 m (site ZD′), but not at 3420 m (site ZR′) where the channel was too deep. Lastly, the mooring line broke at site ZD′ in October 2004 probably due to a strong event like that of 2001 previously described by Khripounoff et al. [

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