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Clay fraction distribution in the sediments of the Senegal River Estuary after the Diama (Senegal) dam construction.

Abstract – Clay fraction contents distribution in the Senegal River estuary after the building of the anti-salt Diama dam has shown that upstream sediments are very muddy. Clay fraction content is as high as 60 % of sediments in the middle of the channel with a pronounced downstream decreasing trend on the banks comparing to the contents in the middle of the channel. Towards the river mouth, the fine fraction tends to disappear leading to a shelly sand sediments type essentially. During low stage period, clay fraction contents increase particularly at the vicinity of the dam reservoir. In opposite, in the estuarine reach, downstream the dam, the increasing trend is particularly marked in the middle of the channel. The clay minerals assemblage shows that kaolinite and smectite are the main components, whereas interlayered illite-smectite and illite are minor constituents. The upstream-downstream profile shows a decrease in kaolinite content although it remains the dominant constituent. Suspended clay minerals (smectite and illite-smectite) concentrate rather in the middle of the channel and on the right bank where the water depth is higher. Thus, it is likely that during low stage water, distribution of these clay minerals often correlate with the contents of the entire clay fraction with an increase during low stage water period. This hydrodynamic sorting of the suspended minerals which is more marked at the dam reservoir tends to disappear in the estuarine reach between Diama dam and the river mouth. Despite that, clay minerals assemblage shows a rather homogeneous composition which does not seem to be altered by the seasonal fluctuations.

Pages : 35-45
Année de publication : 2016
Revue : Journal of Shipping and Ocean Engineering
N° de volume : 6
Type : Article
Mise en ligne par : DIOUF Mouhamadoul Bachir