Geochemical evidence of provenance diversity in Holocene sandy land of Qinghai Lake Basin in the north‐eastern margin of Qinghai–Tibet Plateau and its implications for climate change

Abstract

ABSTRACTThe Qinghai Lake Basin, located in the north‐eastern Tibetan Plateau, is crucial for understanding the East Asian monsoon evolution and its interaction with westerlies. Palaeoclimatic studies in this region since the Holocene have primarily focused on interpreting proxy significance from sediments, resulting in being highly controversial. However, exploring palaeoclimate evolution through sediment provenance and proxy integration remains rare. This study analysed the elemental geochemical properties of two fluvial–lacustrine–aeolian profiles in Hudong Sandy Land, east of the Qinghai Lake Basin, and compared these with published modern basin sediments and extensively investigated Late Quaternary aeolian deposits. It was found that Hudong Sandy Land sediments exhibit similar geochemical compositions to other modern basin sediments, primarily consisting of SiO2, Al2O3 and CaO. Contrary to previous understanding, lacustrine sediments in the Hudong Sandy Land are closer to the upper continental crust average than aeolian deposits. Geochemical ratios and parameters suggested that Hudong Sandy Land sediments primarily derived from mixed source rocks of felsic igneous, quartzose sedimentary and intermediate igneous provenances. A comparison with published elemental geochemical data from the basin reveals distinct sediment sources during different periods in the Hudong Sandy Land. From 9.6 to 4.0 ka bp, Hudong Sandy Land hosted numerous lake environments, with sediments displaying a dominant role in sedimentary recycling and reworking, implying a continuously stronger East Asian summer monsoon. During 8.2 to 5.1 ka bp, the Hudong Sandy Land was a fluvial depositional sink for sediments from the Dabanshan Mountains. Bedrock clastic material generated by intense erosion and monsoonal runoff transport contributed to Hudong Sandy Land sedimentation, indicating the East Asian summer monsoon's peak since 9.6 ka bp. After 4.0 ka bp, thick aeolian sands accumulated in the Hudong Sandy Land, primarily derived from Lake Qinghai sediments due to declining water levels, indicating that westerlies and East Asian winter monsoon dominated the basin, with a weaker East Asia summer monsoon. This study facilitates a deeper understanding of the interaction between the East Asia summer monsoon and East Asia winter monsoon/westerlies.