A total of 83 cores were collected in the Gulf of Lions continental margins and analysed for 210Pbxs (excess 210Pb) in order to understand sedimentation patterns. Apparent sedimentation rates (ASR) range from 0.65 cm year-1 in the vicinity of the Rhône River mouth to 0.01 cm year-1 in the deep basin. Except for the prodelta area, rates decrease with depth linearly with the water depth. On the slope, ASR do not differ between canyons and open slope, except for the western area where the rates are slightly higher in the Lacaze-Duthiers canyon compared to its adjacent, open slope. In the canyon and open slope areas, mass accumulation rates determined from 210Pbxs profiles (0.10 and 0.08 g cm-2 year-1, respectively) are in good agreement with particulate fluxes calculated from 5 years of near-bottom sediment trap data, even when the trap particle fluxes and the apparent accumulation rates are overestimated in response to resuspension and bioturbation effects. However, differences in sediment trap data, between west and east portion of the slope, are not observed in the sedimentation rates calculated with 210Pbxs. The outer shelf area may have an important role in trapping sediment but it is not sufficiently documented. Sediment surface mixed layer depths decrease with water depth, with a mean value for the whole margin of 8±6 cm. 210Pbxs inventories in the sediment are systematically higher than the net 210Pb export flux estimated from the above water column. Over the margin, the ratio between accumulated 210Pb and available 210Pb is about 3, suggesting boundary scavenging effects and advective transport.
a CEREGE, UMR 6635, CNRS-Univ. Paul Cézanne, BP 80, F-13545 Aix-en-Provence, France
b CEFREM, Université de Perpignan, 52 Av. P. Alduy, F-66000 Perpignan, France
c IRSN, Base IFREMER, BP 330, F-83570 La Seyne-sur-mer, France