Vertical distribution of suspended particulate matter in the Zaire river, estuary and plume

Abstract

Light transmission and hydrographic data were measured in situ simultaneously in the Zaire river estuary and on the shelf off the river extending to the Angola Basin. Profiles of light transmission indicate that the majority of the particles derived from the river are transported offshore into the Angola Basin through deep waters under the surface plume. The Zaire river is associated with a submarine canyon which extends well into the Zaire estuary and cuts across the shelf. Bottom nepheloid layers were well developed along the canyon axis. The sediments along the canyon axis were mostly sands, and thus the submarine canyon appears to provide an efficient transport route of fine-grained material to the Angola Basin across the shelf. The surface plume is so highly stratified that vertical mixing appears very limited across the plume boundary, and downward transport of suspended particles must be accomplished by particle settling. Profiles containing small-scale layers of turbid water under the surface plume are considered indications of settling particles from the surface river plume.