Late Pleistocene Continental Climate and Oceanic Variability Recorded in Northwest Pacific Sediments

Abstract

Core V21‐146 provides a continuous record of northwest Pacific pelagic sedimentation spanning the past 530,000 years. Downcore variations of δ18O from benthic foraminiferal calcite were correlated to the SPECMAP record to provide an age model for late Pleistocene paleoclimatic and paleoceanographic variation. Fluxes of CaCO3 and eolian material have been determined by combining information about linear sedimentation rates, bulk densities and component percentages. The mass accumulation rate (MAR) of CaCO3 varies from 58 to 1435 mg(cm² kyr)−1 and exhibits the Pacific Ocean pattern of higher accumulation associated with glacial periods for the younger portion of the record. However, the pattern of CaCO3 accumulation appears to shift during the mid‐Brunhes so that prior to 350,000 years ago it exhibits an opposite pattern of greater accumulation during interglacial periods. The flux of eolian dust is a proxy measure of the source area aridity and correlates well to the loess‐soil stratigraphy in China. Dust fluxes range from 43 to 718 mg(cm² kyr)−1 and are greater by a factor of about 4 during glacial times. Cross‐spectral analysis of the eolian flux and oxygen isotope records shows an inphase and coherent relationship at each of the major orbital periodicities of 100, 41, and 19 kyr. Eolian grain sizes, generally used as a proxy record of wind intensity, range from 8.4ф (2.9 µm) to 6.2ф (13.6 µm). A change in grain size variability occurs near about 300 ka such that the older portion is characterized by lower‐frequency and higher‐amplitude fluctuations than the younger portion. Power spectra for the eolian grain size record show dominant peaks at 100 and 50 kyr and a broad 25–35 kyr peak but coherency to the oxygen isotope curve at only the 100 and 33 kyr periodicities. The phase relationship for eccentricity between the eolian grain size and δ18O records suggests that at the 100 kyr frequency the smallest grain sizes are associated with glacial conditions.