Quantitative estimation of provenance contributions to loess deposits in Eastern China and implication for paleo-dust storm activity

Abstract

Improvement in the current knowledge regarding the provenance of loess deposits could clarify complex depositional processes, as well as provide new insights into the paleo-dust storm history in dust source areas. In this study, a comprehensive analysis of the size-differentiated geochemical compositions and zircon UPb ages of the examined loess deposits assisted in deepening the provenance identification of the Xiashu loess in Eastern China. It was first reported that the fine-grained components of the Xiashu loess were mainly derived from the arid region of the Asian interior via the paleo-dust storms, as supported by consistent geochemical compositions of <5 μm components between the Xiashu loess and the Luochuan loess. It has been demonstrated that the geochemical compositions of the 10–20 μm and 20–50 μm components and the zircon (> 40 μm) UPb age distributions of the Xiashu loess were very similar to the Yangtze River sediments, revealing that the >10 μm components of the Xiashu loess were sourced from the local floodplains of the Yangtze River's downstream regions. Furthermore, a new method of combination of provenance results of the size-differentiated fractions and quartz grain-size contents was proposed to quantitatively estimate the Xiashu loess sources. Results of the quantitative evaluations showed that at least 82.43% of the components in the Xiashu loess were the result of nearby-source transport processes and approximately 9.64% were from distant-source transport processes. We thus conclude that the activities of local ancient dust storms dominated the aeolian deposition system in the eastern plain of the Yangtze River Delta. However, it was determined that the long-range transported dust via ancient sandstorms in Asian inland cannot be ignored because fine-grained dust has important impacts on climate, ecological environment, and human health.