Sr-Nd isotopes as tracers of fine-grained detrital sediments: the South-Barbados accretionary prism during the last 150 kyr

Abstract We studied a core retrieved from the deformation area of the South-Barbados accretionary prism. Sr and Nd isotopic ratios were used in conjunction with the clay mineral assemblage to determine the origin and fluxes of fined-grained detrital material and the sedimentological processes in this area during the last 150,000 years. During the high sea-level stands of events 1.1, 3.3 and stage 5, sedimentation was mainly fed by Amazon material conveyed by the Guiana Surface Current and by volcanogenic material transported by the southward flowing North Atlantic Deep Water (NADW); the flux of clays were very low ( −2 10 −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 and transported directly by turbidity currents, indicate an important change in sedimentary processes. The high flux of volcanogenic materials (0.9 g cm −2 10 −3 yr at event 2.2) indicates the importance of air-fall ashes from Dominica, Guadeloupe and/or Martinique islands and of the NADW as the transport agent. The importance of allochthonous fine-grained material originating from the South-American continent (Andes or Guiana Shield) and the northern part of the Lesser Antilles arc clearly stresses the major role that climate and eustacy had on detrital sedimentation during the last climatic cycle.