Provenance of Quaternary aeolian silts in western China and its spatial difference with source of the Yellow River sediments

Abstract

Quaternary aeolian silts in the Chinese Loess Plateau (CLP) has long been regarded as a product of sand ablation during the process of transportation originally from sandy deserts of northern China and Mongolian Gobi deserts driven by winter monsoon. Recently, this traditional idea was challenged by a new idea that aeolian silts in the CLP were emitted from fluvial sediments in the middle reaches of the Yellow River which was originally transported from the Tibetan Plateau ascribed to intensified Asian summer monsoon. We systematically determined the origin of Quaternary aeolian silts in a 318-m-thick loess/palaeosol sequence by using U–Pb age spectrum of detrital zircon grains, and compared it with Quaternary fluvial sediments on the Yellow River terraces in Lanzhou, western CLP. The aeolian silts were originated from Qilian Mountains in Northeastern Tibetan Plateau since 1.4 Ma with exception in the intervals of 1.02–0.93 Ma, ∼0.75 Ma and ∼0.06 Ma when aeolian silts were originated from Gobi-Altai Mountains. In contrast, Quaternary fluvial sediments of the Yellow River were mainly originated from Songpan block south to the Qilian Mountains. We propose that the Quaternary aeolian silts in western CLP were emitted and transported by winter wind circulation from piedmonts of the Qilian Mountains more than by the Yellow River from the Songpan block to the south. This study promotes the recognition in terms of the source of the Quaternary aeolian silts in western China.