SR-ND ISOTOPES AS TRACERS OF FINE-GRAINED DETRITAL SEDIMENTS - THE SOUTH-BARBADOS ACCRETIONARY PRISM DURING THE LAST 150 KYR

We studied a core retrieved from the deformation area of the South-Bar bados accretionary prism. Sr and Nd isotopic ratios were used in conju nction with the clay mineral assemblage to determine the origin and fl uxes of fined-grained detrital material and the sedimentological proce sses in this area during the last 150,000 years. During the high sea-l evel stands of events 1.1, 3.3 and stage 5, sedimentation was mainly f ed by Amazon material conveyed by the Guiana Surface Current and by vo lcanogenic material transported by the southward flowing North Atlanti c Deep Water (NADW); the flux of clays were very low (< 0.2 g cm(-2) 1 0(-3) yr), except during stage 5 (0.7 g cm(-2) 10(-3) yr). During the low sea-level stands of events 2.2, 4.2, 5.2, 5.4 and 6.4 and stage 5, the appearance of Orinoco material (1.5 g cm(-2) 10(-3) yr at event 2 .2), primarily derived from granitic batholiths of the Guiana Shield a nd transported directly by turbidity currents, indicate an important c hange in sedimentary processes. The high flux of volcanogenic material s (0.9 g cm(-2) 10(-3) yr at event 2.2) indicates the importance of ai r-fall ashes from Dominica, Guadeloupe and/or Martinique islands and o f the NADW as the transport agent. The importance of allochthonous fin e-grained material originating from the South-American continent (Ande s or Guiana Shield) and the northern part of the Lesser Antilles are c learly stresses the major role that climate and eustacy had on detrita l sedimentation during the last climatic cycle.