19. UPPER NEOGENE AND QUATERNARY PLANKTONIC FORAMINIFERS FROM THE BLAKE OUTER RIDGE AND BLAKE-BAHAMA BASIN (WESTERN NORTH ATLANTIC), DEEP SEA

Four holes were drilled at two sites in the western North Atlantic during Deep Sea Drilling Project Leg 76. Thick Pliocene-Quaternary sediments were continuously cored in Holes 533 and 533A, located on the Blake Outer Ridge. A detailed biostratigraphic study of the upper Neogene and Quaternary strata has been made using distribution of plank-tonic foraminifers. Precision of the biostratigraphic analysis enabled us to trace fluctuations of the sedimentation rate closely. Very high mid-Pliocene input strongly contrasts with the extreme condensation that was noted to have occurred during the latest Pliocene. Quantitative micropaleontology methods have been applied to selected planktonic species or groups of foraminifers, enabling us to discern clearly the oceanic response to large-scale climatic changes, such as the mid-Pliocene glacial event and the Quaternary cycles. In contrast, the small-scale climatic events appeared to be ob-scured by minor sedimentary disturbances, which could be related to bottom contour-following currents