The nature of varved sedimentation in the Cariaco Basin, Venezuela, and its palaeoclimatic significance

A laminated sediment record of the last 12 600 radiocarbon years from the anoxic Cariaco Basin provides a rare opportunity to study interannual to millenial-scale climatic change in a marine setting. Sedimentological and radiometric analyses of laminae couplets in the basin sediments indicate that they are annually deposited varves. The varves consist of light and dark laminae which are deposited as the result of the Intertropical Convergence Zone's annual north-south migration over the tropical North Atlantic, and the impact of this migration on regional upwelling and rainfall patterns. Varve measurements developed using X-ray images and thin sections indicate that a continuous 14 000 calendar year long varve chronology may be generated. Palaeoclimatic inferences are described.