The Sr-Nd isotope geochemical tracing of Xiashu Loess and its implications for the material transport mechanism of the Yangtze River

摘要

The Xiashu Loess along the middle and lower reaches of the Yangtze River in China is of considerable significance for revealing regional and global climatic and environmental changes since the middle Pleistocene. This study used Sr-Nd isotopic in three different particle fractions (<2 mu m, 2-75 mu m and >75 mu m) to investigate the provenance of Zhoujiashan Xiashu Loess in China, which is essential for understanding the paleoenvironmental conditions. The epsilon(Nd)(0) value ranges from -10.2 to -13.4, and the Sr-87/Sr-86 ratio value varies from 0.714120 to 0.750325. As particle size increases, the epsilon(Nd)(0) value of the loess does not change significantly, and the Sr-87/Sr-86 ratio value of the loess decreases significantly. The Sr-87/Sr-86 ratio and epsilon(Nd)(0) value show a negative correlation. The epsilon(Nd)(0) values of the Xiashu Loess in different fractions are similar to those of the sediments in the Yangtze River and lower than that of loess from the Lingtai section in Northern China, which suggests that both coarse and fine dust come from the nearby river valley. The temporal variation in the Sr-Nd isotopic composition of loess from Zhoujiashan during the past 0.9 Ma reflects the material transport mechanism of the Yangtze River Basin may be the main cause of the aeolian deposition under the influence of the monsoon climate. Therefore, we suggest that the material transport mechanism has been driven by regional climate change in the Yangtze River Basin since 0.9 Ma, and this mechanism is the main reason for aeolian deposition.