Late Quaternary aeolian dust input variability on the Chinese Loess Plateau: inferences from unmixing of loess grain-size records

Abstract

The grain-size distributions (GSDs) of loess–paleosol sequences may provide valuable information on provenance, transport and paleoclimate variability, and consequently, a wide range of methods to extract genetic information from loess GSDs has been proposed. Here it is shown that a genetically meaningful decomposition of a series of Late Quaternary loess grain-size records extending across the Chinese Loess Plateau can be accomplished with the end-member modelling algorithm (EMMA). The unmixing results in conjunction with loess accumulation rate estimates reveal that two contrasting dust supply patterns were active over the Loess Plateau during the last glacial–interglacial cycle: (i) a background sedimentation pattern that was dominant during interglacial periods, especially over the central and southern parts of the Loess Plateau, is reflected by the constant flux of the fine-grained loess component, (ii) an episodic, highly variable dust input pattern, that was dominant during glacial periods throughout the Loess Plateau and noticeable during interglacial periods mainly over the northern Loess Plateau and almost disappearing over the southern Loess Plateau, is reflected in the admixture of two coarse-grained loess components. A genetic interpretation and the paleoclimatic significance of the mixing model are provided by comparison of the modelled end members with modern dust samples in terms of their GSD and flux rates.