Provenance of Aeolian Sediments in the Ordos Deserts and Its Implication for Weathering, Sedimentary Processes

Guoxiang Chen,Weikang Shi,Weige Nan,Tianjie Shao,Junhuai Yang,Chao Li,Zhibao Dong

doi:10.3389/feart.2021.711802

Guoxiang Chen, Weikang Shi + Show 5 more

Open Access

https://doi.org/10.3389/feart.2021.711802

Copy DOI

Abstract

Identifying the provenance of aeolian deposits in semi-arid zones of China is beneficial in understanding Earth’s surface processes and helping to alleviate ecological stress. In this paper, we use grain-size, geochemical elements, heavy-minerals, and quartz grain morphology data to investigate the potential source of aeolian sands from the Ordos Deserts (Mu Us Sandy Land and Hobq Desert). Sedimentological, geochemical and geomorphological results indicate that significant provenance differences exist among various parts of the Mu Us Sandy Land, i.e., aeolian sediments from the southwest region are obviously distinct from other areas in the Mu Us Sandy Land but show the same external provenance with the Hobq Desert referring to the sorting, mineralogical maturity, geochemical characteristics, heavy-minerals, and quartz grain morphology. Comparing the samples from the Ordos Deserts with felsic rocks from potential sources via a serious of geochemical methods, we conclude that: 1) Aeolian sands from other regions of the Mu Us are a mixture of binary provenance, i.e., one originated from local lacustrine sediments and underlying sandstones, and another from the Alxa Plateau (AP) carried by northwesterly Asian winter monsoon. 2) The fluvial deposits denuded from the Qilian Orogenic Belt in the Northeastern Tibetan Plateau (NTP) and carried by the Yellow River are likely the initial material source for the southwest region of the Mu Us Sandy Land and the Hobq Desert. 3) The Yellow River plays a significant and critical role in sediment transport for sand seas in arid and semi-arid areas of northern China.

Highlights

Desert sand seas, characterized by various dune types, make up a significant part of the Earth’s surface sediment systems (Goudie and Middleton, 2001)
The quartz grains in the upper Yellow River displays typical aqueous characteristics such as V-shaped fractures and conchoidal fractures (Pan et al, 2016). Such characteristics resulting from the action of aqueous processes are found in the southwest region of the Mu Us (Supplementary Figure S3), but the edges of these features tend to be smooth, indicating that the sand has been affected by aeolian activities after being transported to the sedimentary area by fluvial processes (Figure 8). These results provide overwhelming evidence to conclude that the detrital sediments brought by the Yellow River from the Northeastern Tibetan Plateau (NTP) provide the sediments for the Hobq Desert and the southwest region of the Mu Us
The evidence obtained by other methods support this conclusion, i.e., the heavymineral assemblages and mineralogical maturity, the content of major, trace, and rare Earth elements (REE) elements, the surface micro-textures of quartz grains of southwest region in the Mu Us Sandy Land and the Hobq Desert shows similarity, but their characteristics are obviously different from other regions of the Mu Us

Summary

Introduction

Desert sand seas, characterized by various dune types, make up a significant part of the Earth’s surface sediment systems (Goudie and Middleton, 2001). Previous studies have demonstrated that extensive sand seas in northern and western China are a significant component of the Asian aeolian dust system (Chen and Li, 2011) Dust from these areas has drawn widespread public attention because of its potential influence on the Asian. Tracing the provenance of aeolian sediment is fundamental to understanding the formation and evolution of deserts, the interaction between surface processes and climatic changes, the operation of the Earth system (Molnar, 2004). It is beneficial for establishing effective environmental governance policies for such sensitive areas in China (Du et al, 2018). Some peculiar morphologies related to specific sedimentary processes and environments can be discriminated by the analysis of quartz grains using SEM, which provides new insights into the provenance of the sediments (Moral Cardona et al, 2005)

Objectives

Methods

Conclusion