Provenance of fine-grained Quaternary sediments in the Tengger Sandy Desert recorded by Sr-Nd isotopes and its linkage with Quaternary aeolian silts on the Chinese Loess Plateau

Abstract

Aeolian dust, a product of aridification, can directly affect the climate system by reflecting and absorbing solar radiation, or indirectly by altering cloud properties. It also plays a role in regulating carbon uptake in marine ecosystems through the iron fertilization effect. The Gobi Deserts in southern Mongolia have traditionally been considered major sources of sandstorms and dust emissions in Asia's interior. However, a recent sediment tracing study using U-Pb age spectra of coarse detrital zircon grains challenges the role of these sandy deserts as sources of aeolian dust for the downwind Chinese Loess Plateau (CLP). This study aimed to identify the provenance area of Quaternary fine-grained sediments in the proximal sandy Desert Tengger and to explore their potential link with aeolian dust in the downwind CLP during the Quaternary. (1) 87Sr/86Sr values ranging from 0.715124 to 0.728164 and 143Nd/144Nd values from 0.511987 to 0.512192 were measured in the acetic acid-insoluble <75 μm fraction of 30 Quaternary sediment samples from the core BJ14, drilled in the Tengger Sandy Desert hinterland. (2) These 143Nd/144Nd values resemble those of riverine sediments eroded from rocks in the Northern Qinghai-Tibet Plateau (NTP) but differ from those eroded from the Gobi Altai Mountains (GAMs). This indicates that the NTP is the primary source of the <75 μm component of the Tengger Sandy Desert sediments during the Quaternary. Alongside previous studies on U-Pb age spectra of detrital zircons, our results suggest that after 0.8 Ma, the contribution of fine-grained detritus from the NTP decreased, although it continued to dominate the provenance of fine-grained sediments. However, the contribution of coarse detritus from the NTP increased significantly, becoming predominant in coarse grains, especially after 0.36 Ma. These changes record enhanced physical weathering and wind transporting capacity driven by temperature differences in the context of global aridification following the Kunlun-Huanghe Movement and the Mid-Pleistocene Transition. (3) After 0.9 Ma, a deviation on 143Nd/144Nd values of the <75 μm Quaternary sediments within the hinterland of Tengger from that of the 28–45 μm fraction in the loess/paleosol sequence in Lingtai in the central CLP suggests that the source-sink linkage between the hinterland Tengger and Chinese Loess Plateau was weak after 0.9 Ma. But high shoreline areas of the paleolake Tengger might be a persistent source area emitting fine-grained detritus to the CLP throughout the Quaternary period. This study indicates further research is needed to enhance our understanding of dust fluxes in northern China.