Provenance of sub-aerial surface sediments in the Tarim Basin, Western China

Abstract

Provenance of surface sediments in the Tarim Basin is important for understanding the aridification of the Asian interior and the interplay between the Westerlies and the Asian monsoon. Although the desert sands in the Taklamakan Desert have been studied intensively, there is no consensus regarding their provenance, namely, the dispute exists between various sand sources in different parts of the desert and homogenization of the sands in the entire desert. Moreover, other surface sediments in the basin are poorly investigated. Here we examine the particle-size-specific rare earth element (REE) and trace element characteristics of various surface sediments from different regions of the basin. The results reveal that the <2 µm fraction has multiple sources from Central Asia as well as from the adjoining arid/semi-arid areas to the east, together with the abrasion of coarser particles from multiple regional sources. They are completely homogenized prior to deposition by the action of the Westerlies and the local wind systems. The 2–16 µm fraction of most of the sediments in the basin have a higher proportion of Central Asian dust and a relatively high degree of homogeneity. Westerlies and local wind systems remain a more important transport mechanism than the fluvial activity. In addition, the desert sands of 2–16 µm fraction in the Taklamakan Desert has a substantial contribution from material derived from the basement rocks. The 32–63 µm and >63 µm fraction are dominated by regional-derived materials, mainly from the adjacent mountains (e.g. Pamirs, Kunlun, Kuruktag, Altun, Tianshan Mountains), and the fluvial systems are an important additional transport mechanism. Our findings potentially provide an improved understanding of the dust cycle and atmospheric circulation patterns in Central Asia, and of the provenance of loess in North China.