A 47.0-kyr Record of Strontium and Neodymium Isotopes of the Lake Sediments from Dahu Swamp in East Nanling Mountains (South China): Implications for the Source of Sediments and Climatic Changes

In this study, we used a similar to 47.0-kyr record of Sr-Nd isotopic data derived from lake sediments in Dahu swamp in the eastern Nanling Mountains to explore the possible changes in the source of sediments, and to provide insights into the East Asian winter monsoon (EAWM) driven climatic signals. Based on Sr-Nd isotopic results, we argued that local weathered granitic residues were the dominant source of sediments throughout the past similar to 47.0 kyr. However, variations of Sr-87/Sr-86 and Nd-144/Nd-143 ratios were likely disturbed by the mixture of an additional input from Chinese Loess Plateau (CLP). During some dry/cold millennial periods (e.g., Hein-rich event 5, 4, and 2, and the 26.0-24.0 kyr B.P), similar Sr-Nd isotopic signatures between the lake sediments and the fine fraction (<20 mu m) of the loess from CLP implied an aeolian dust source. Thus, variability of Sr-Nd isotopic ratios indirectly indicated two modes of climate patterns: the wet and warm intervals during which the sediments were mainly derived from the local weathered residues were expressed in increased Sr-87/Sr-86 and decreased Nd-144/Nd-143 ratios, whereas during the dry and cold intervals the increased input of fine dust from CLP transported by strengthened EAWM winds would favor declined Sr-87/Sr-86 and increased Nd-144/Nd-143 ratios. Our Sr-Nd isotopic records revealed an anti-phase between the EAWM and the summer monsoon, and displayed a good consistency with the record of mean grain size of quartz of loess from CLP, which was regarded as a reliable proxy of EAWM, suggested they can indirectly reflect variability of EAWM strength.