Early and middle Holocene climate evolution inferred from peat mercury and humification in the Altai Mountains, northwestern China

Holocene climate variability in inland Asia remains unclear. The reconstruction of long-term mercury atmospheric deposition in peat has great potential for identifying climate change. Here, we present the results from a peat plasa in the high-elevation regions of the Altai Mountains, Xinjiang, China, with a time span of 5000 years (10.5–5.5 cal kyr BP) obtained by ¹⁴C AMS dating. The peat profile was analyzed for mercury content and thermal lability, degree of humification, and tracers of mineral matter (Al, Ti, and Zr) flux. The results show that the mercury concentration is strongly influenced by atmospheric dust deposition. The reconstructed patterns of high thermal stability of mercury (H-Hg) associated with temperature changes strongly correspond to regional dust deposition, which indicates that the region experienced a general warming and drying climate trend during 10.5‒5.5 cal kyr BP. Spectral analysis of the H-Hg record revealed significant periodicities at approximately 450, 255, 96, 74, and 68 years, which correspond with solar activity cycles, suggesting that solar forcing may have been the major centennial-scale driver of climate variability in the Altai Mountains. The results shown here provide further evidence that the H-Hg concentration in peat can be a useful tool for paleotemperature reconstruction.