East Asian monsoon variation during the last 130,000 Years: evidence from the Loess Plateau of central China and Lake Biwa of Japan

Abstract

The loess–paleosol sequence on the Loess Plateau of central China constitutes an excellent proxy record of variations in Asian monsoon climate over the past 2.5 Ma. Magnetic susceptibility of loess and paleosols has been used as a proxy indicator for summer monsoon intensity, while the median diameter of quartz isolated from the loess and paleosols has been regarded as a proxy index of the strength of winter monsoon winds that were responsible for most of the dust transport. The eolian quartz flux to Lake Biwa of central Japan during the last 130,000 yr provides direct information on variations of the East Asian winter monsoon; whereas the fluvial quartz flux reflects significant changes in paleoprecipitation over the lake area. The intervals of high eolian quartz flux values during marine oxygen isotope substages 5d and 5b, and stages 4 and 2 correspond to the periods of large quartz median diameter values of the Chinese loess and paleosols, indicating strengthened winter monsoon winds; whereas the intervals of high fluvial quartz flux values during isotope substages 5e, 5c, and 5a, and stages 3 and 1 correlate to the periods of high magnetic susceptibility values of the Chinese loess and paleosols, suggesting increased summer monsoon intensity. Variations in winter monsoon strength indicated by the eolian quartz flux and quartz median diameter proxies bear a general inverse relation to those in summer monsoon intensity inferred from the fluvial quartz flux and magnetic susceptibility proxies.