(Table 1) Distribution of 210Pb in the surface layer of shelf sediments near the Congo mouth and sedimentation rates

A constant concentration model was used in conjunction with the nonequilibrium 210Pb method in determining mean sedimentation rates of bottom sediments sampled during Cruise 20 of R/V Vityaz-II in a test range occurred on the Atlantic shelf near the Congo mouth. 210Pb distribution was analyzed at 16 stations located within a canyon, which is an extension of the Congo channel, and on its shoulders. On the canyon floor at depths 1 km within 12-15 cm sampled sediment monoliths it was possible to detect sediments re-deposited from the canyon walls characterized by high 210Pb concentrations. Sedimentation rates of the surface layer of sediments vary in the range 0.065-0.290 cm/year with the mean value 0.141+/-0.083 cm/year. At most stations the analysis of 210Pb distribution indicates presence of re-deposited matter. Integral activity of 210Pb was used to mark five stations with sediment accumulation regime close to that in the adopted model. Sedimentation rate for these five stations is 0.082+/-0.024 cm/year.