Transformation of lakebed into a major soluble-salt-bearing dust source for Asia since the mid-pleistocene

Abstract

Loess in the Chinese Loess Plateau (CLP) preserves abundant information about the dust cycle over Asia. However, the variations of loess source and composition over time remain controversial. Soluble salt is an important dust component and is linked to the landforms and environments associated with dust mobilization, transport and deposition. Based on an investigation of the soluble salts of two loess sequences from the central and western CLP, we show that the soluble salts of Chinese loess mainly stepwise increased at ∼1 and ∼ 0.5 Ma. Several lines of evidence indicated that the increased supply of soluble salts mainly originated from dust input, suggesting the enhanced salinity of Asian dust. The enhanced soluble-salt-bearing dust was driven by lakebed evolution in the potential source areas, as confirmed by abundant geomorphological and sedimentological evidence. The Mid-Pleistocene Transition (associated with Tibetan Plateau uplift) induced aridity of the potential source areas (PSA) and Mid-Brunhes Transition triggered intensifying East Asian summer monsoon are responsible for the stepwise lakebed evolution in the PSA at ∼1 and ∼ 0.5 Ma, respectively, which in turn acted as an important soluble-salt-bearing dust reservoir. These findings provide new evidence for understanding the evolution of regional dust emissions and their possible environmental effects in the past and future.