Quantification of Middle to Late Holocene precipitation in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau, from the geochemistry of aeolian surface soil

The Northeastern Qinghai-Tibetan Plateau (QTP) is situated in the climatically sensitive intersection of the Asian summer and winter monsoons and the westerlies. However, due to the lack of a well-defined relationship between aeolian deposits and climatic factors in this region, there are few quantitative palaeoclimate reconstructions from these deposits. This deficiency prevents a comprehensive understanding of the precipitation history of the alpine and arid/semi-arid intermontane basins in this region, although the regional landscape is dominated by deserts/dunefields. We studied the relationship between two geochemical indices, C (the ratio of (Fe + Al + Mn + Cr + Co + Ni) to (Ca + Mg + Na + K + Sr + Ba)) and Re (the ratio of (CaO + MgO + K2O + Na2O) to (Fe2O3+MnO2)) of the aeolian topsoils and potential modern climatic variables across the Gonghe Basin in the northeastern QTP. We found that the mean annual precipitation (MAP) is the dominant climatic control of the variations of C and Re in the surface aeolian deposits, accounting for 70.9% and 53.1% of the total explained variances, respectively. Accordingly, we established two climofunctions based on C and Re to quantitatively reconstruct the MAP evolution during the Middle-Late Holocene, from the alternating aeolian sand-palaeosol sequences in the Gonghe Basin. The results revealed five intervals of enhanced MAP, with similar results obtained from the two sections, which document millennial-centennial-scale climatic fluctuations during the Middle-Late Holocene. These fluctuations are consistent with climate records from tree rings and lake sediments in this region, within the dating errors. This consistency supports the reliability of our methodology of quantitative reconstruction based on geochemical climofunctions for aeolian deposits. Our findings demonstrate a robust approach for the quantitative reconstruction of palaeo-precipitation using geochemical parameters from aeolian topsoils in an alpine and arid/semi-arid intermontane basin, and they provide new evidence for understanding significant Holocene environmental events recorded in different geological archives within the transitional region of the monsoon and the westerlies.