Coeval changes in grain size and sedimentation rate of eolian loess, the Chinese Loess Plateau

To determine the temporal-spatial relationship between strength of the wind s transporting the Chinese loess and aridity conditions of the loess source area, six loess sections located respectively in the northern, middle, and southern Loess Plateau were studied. Grain size distributions were analyze d on loess-paleosol samples that are closely spaced in the sections. Time s cales were established by tuning each of the grain size records to theoreti cal changes in the Earth's orbital parameters. Results obtained show that d uring the last two glacial cycles, particle size of the loess co-varies wit h apparent sedimentation rates, suggesting that variations in winter monsoo n intensity and the aridity of the loess source area are tightly coupled. T his proximal relationship is in striking contrast with the observation of d istal eolian clays in North Pacific sediments. We propose that this phenome non may result from the proximity of the Loess Plateau to the source area a nd from the significant control of the winter monsoon on the expansion-retr eat changes of the deserts in the northern and northwestern China.