Cenozoic mass accumulation rates in the equatorial Pacific based on high-resolution mineralogy of Ocean Drilling Program Leg 199

Abstract

We use continuous mineralogy logs derived from multisensor track physical properties data and reflectance spectroscopy to calculate high-resolution carbonate, opal, and terrigenous mass accumulation rates (MAR) for the eight sites cored during Ocean Drilling Program Leg 199 in the equatorial Pacific. The largest change in equatorial Pacific sedimentation patterns of the last 55 Myr occurs at the greenhouse/ icehouse transition, shortly after the Eocene/Oligocene boundary. Calcite compensation depth deepened dramatically, the equatorial zone of opal accumulation narrowed, and the in tertropical convergence zone shifted to the equator. During the Paleogene the opal equatorial accumulation bulge extended to about 12°N, whereas the Neogene bulge extended only to about 7°N. Very low Eocene carbonate MAR was followed by much higher Oligocene and early Miocene MAR, with the carbonate equatorial bulge extending to 4°N. Terrigenous MARs indicate the paleoposition of the intertropical convergence zone and a Pliocene-Pleistocene increase in Asian dust flux. Copyright 2004 by the American Geophysical Union.