The long-term paleomonsoon variation recorded by the loess-paleosol sequence in Central China

Abstract

The loess-paleosol sequence in Central China during the last 2.5 Ma is a good record of the Asian monsoon variation, which could be considered as the concrete realization of global paleoclimatic cycles. The geological and biological evidence of the loess-paleosol sequence indicates that the loess was mainly the dust deposits transported by the northerly wind of winter monsoons and also suffered to some extent from pedogenesis caused by weakened summer monsoons, and that the paleosol accreted by the rather slow dust accumulation was closely related to strengthened summer monsoons. An alternating occurrence of loess and paleosol in the Luochuan section implies the variation history of warm-humid climate with a summer monsoon dominance and cold-dry climate with a winter monsoon dominance. The magnetic susceptibility of loess and paleosol can be regarded as a proxy index of Asian monsoon variation. An analysis of the susceptibility curve and structure characters of Luochuan section shows that the Asian monsoon circulation was strengthened from Early Pleistocene to Late Pleistocene, and the 500 ka BP point and 1200 ka BP point seem to be a threshold and a turning point respectively in terms of the long-term paleomonsoon variation in Asia.