Late Quaternary climate in southern China deduced from Sr-Nd isotopes of Huguangyan Maar sediments

The hydro-climatic conditions that prevailed during the last Glacial and early to mid-Holocene periods in South China are inferred from chemical compositions and Sr-Nd isotope ratios of sediments from lake Huguangyan Maar and its vicinity. The lake sediments are comprised of organic matter, volcanic materials and aeolian input from nearby granitoid-derived soils. Variations in 87Sr/86Sr ratios in the lake sediments indicate two modes of climate conditions: wet intervals during which the lake sediments are mainly derived from the volcanic-lake rim materials, expressed in low 87Sr/86Sr ratios, and dry intervals during which fine particles from the nearby granitic soils are windblown to the lake and supply local dust expressed in high 87Sr/86Sr ratios in the sediments. These wet and dry intervals generally correspond to regional climate records (e.g., speleothem δ18O profiles in southeast China) and correlate with global climate events (e.g., Heinrich events). While δ18O records of speleothems from southeast China caves are dominated by the precession signal, the Huguangyan Maar Sr record mainly correlates with obliquity. This most likely reflects masking of the precession signal due to regional climate variability, accentuating the obliquity signal. These local effects may also account for some of the differences that have been observed between the various East Asian monsoon records. More importantly, the masking of the precession signal reveals the direct influence of obliquity on the hydro-climate regime in South China.