A new aeolian activity proxy based on analysis of the grain size characteristics of surface soils across the Tengger Desert, northwest China, and its application to a Quaternary aeolian succession

Abstract

The arid regions of northwestern China are dominated by extensive areas of mobile sand dunes. These features cause environmental problems and exert global climatic impacts; however, due to the lack of systematically-applied indicators of aeolian activity, direct evidence of past changes in aeolian activity is unreliable, especially for aeolian sand source regions. In this paper, we analyze the end-member (EM) distributions of various types of surface soil across the Tengger Desert in northwestern China, and devise a sensitive proxy for aeolian activity using a spatio-temporal substitution approach. This proxy is then used to evaluate a Quaternary aeolian succession and to understand the response of aeolian activity to regional climate change. Our results suggest that gradual increases in the coarse-grained EM components 3–5 reflect enhanced dune mobility and reduced vegetation coverage, which are a direct function of the intensity of regional aeolian activity. In the aeolian section, coarse- and medium-grained sand layers resemble modern semi-mobile and mobile dunes, whereas fine-grained sand layers are analogous to vegetated fixed/semi-fixed or semi-mobile dunes. Combining this record with independent multi-proxy evidence from the same section leads us to conclude that strong aeolian activity coincided with a dry climate, sparse vegetation cover, and strong surface winds during the Last Glacial Maximum, and that these conditions gradually attenuated at the beginning of the Last Deglacial. These inferences are in accord with independent paleoclimate records from this region, confirming that the intensity of aeolian activity in the southeastern Tengger Desert is closely associated with large-scale climate change. Our findings show that our EM proxy can be used to infer the intensity of aeolian activity and to reliably reconstruct the evolution of deserts in northwestern China.