中文摘要：

黄土的粒径对于反映古季风强度变化、物源区环境变迁和黄土沉积后改造作用等具有重要的意义。中国东部宁镇地区位于东亚冬、夏季风交汇地带，在晚第四纪普遍发育下蜀黄土，它是研究东亚气候及季风演化的良好载体。对南京周家山、镇江圃山典型下蜀黄土剖面进行了系统的粒度特征分析，结果表明下蜀黄土风尘沉积是由“近源”粗颗粒物质和“远源”细颗粒物质共同作用的产物。周家山剖面粒度组分含量变化记录指示了下蜀黄土所经历的古气候环境较之西北黄土更为暖湿，经历了较之更强的后期风化成壤作用，大致上经历了2次完整的干冷-暖湿气候旋回。

英文摘要：

Loess is one of the most important geological records for the Quaternary paleoclimate changes. Xiashu Loess is distributed in the marginal area of Chinese loess, which could be controlled by cold and warm fluctuations since Late Pleistocene, especially the evolution of East Asia monsoon. On the basis of systematic sampling and analysis of grain size of Xiashu loess in Nanjing-Zhenjiang area, we explored its grain size distribution characteristics. Our results suggest that Xiashu loess follows the zonal distribution of Chinese loess, which is a powerful evidence that the material source of Xiashu loess is far away from local areas. Meanwhile, compared with the Loess Plateau of northwestern China, the higher concentration of its sand grains（8.6%-10.1%）indicates the local source, which could be influenced by the local topography. Vertical profiles of grain size of the Xiashu loess show that the depositional environment of the Xiashu loess was wetter and warmer than northwest inland, and the chemical weathering played a major role in pedogenic processes.