SEDIMENTATION HISTORY OF THE SOUTH PACIFIC PELAGIC CLAY PROVINCE OVER THE LAST 85 MILLION YEARS INFERRED FROM THE GEOCHEMISTRY OF DEEP SEA DRILLING PROJECT HOLE 596

Geochemical analyses of sediments from the top 24.5 m of Deep Sea Drilling Project hole 596 (23 degrees 51.20'S, 169 degrees 39.27'W) show great variability in the composition of pelagic clays accumulated in the South Pacific since the late Cretaceous. Elemental associations indicate that most of this variability can be attributed to variations in abundances of six sediment end-member components: detrital (eolian), andesitic (volcanic) hydrothermal hydrogenous phosphate (fish debris), and biogenic silica. We develop a sedimentation model which is used to infer process that might have influence the accumulation rates of these component over the last 8 5 million years. The accumulation of eolian detritus in the South Pacific shows some similarities to that observed in the North Pacific and has been largely controlled by global climate trends in the Cenozoic. Much of the variation in the accumulation of other sediment component likely reflects the paleoceanographic evolution of the South Pacific. The most notable change in the sedimentary environment occurred at about the Paleogene/Neogene boundary. At that time, significant changes in the color, mineralogy and chemistry of the sediment probably reflect major shifts in climate mode as well as oceanic circulation in the central South Pacific region.