A 15,000 YEAR PALEOENVIRONMENTAL RECORD FROM MEIJI SEAMOUNT, FAR NORTHWESTERN PACIFIC

Late glacial and Holocene hemipelagic sediments from Meiji Seamount in the far northwest Pacific contain common to abundant planktonic and benthic foraminifera for AMS C-14 dating, for stable isotope analysis and for interpreting paleoclimate change. We present here chronostratigraphic, faunal, and geochemical results from a piston core which indicate that during glacial times (as young as 14,000 yrs BP) the northwest Pacific sea-surface salinity was at least as low as today, effectively inhibiting convective overturn. Between 12,000 and 13,000 yrs ago, after a major flux of ice rafting, there is faunal and delta-O-18 evidence of an abrupt decrease in surface ocean salinity. Coincident with this event was an increase in biological productivity, shown by higher fluxes of calcium carbonate, organic carbon, opal, and greater abundances and lower delta-C-13 of the benthic foraminifera Uvigerina. Oxygen isotope ratios in Uvigerina and Cibicidoides show "step-like" decreases at about 13,000-14,000, 11,000-10,000, and 6000-8000 yrs BP. These events may be analogous to steps in the North Atlantic delta-O-18 record during meltwater events. If this interpretation is correct, then the temperature and salinity history of the deep Pacific lags that of the North Atlantic by about 1000 yrs, consistent with the transport time of deep water from the North Atlantic to the North Pacific.