Investigation of Quaternary sediment source and deposition in the Three Gorges area is of critical importance in the study of geological disasters, disaster events, soil erosion and climate change. A ca. 5m thick sediment sequence from the Shidaling section, deposited near eastern Xintan landslide downstream of the Bingshubaojian Gorges, was recently discovered during a geological survey. In this paper, based on the field investigations, profile measurements, combined with systematic grain size analysis, the sediment source and depositional process of the Shidaling section were studied. The results show that: 1) upper sediment of the Shidaling section is mainly composed of size fraction of < 50μm, average content of size fraction of >50μm is 1314% while that of size fraction of between 10 and 50μm is 50%, which is the grain size fraction for the aeolian sediments; 2) grain size parameters, frequency curves and grain size distribution results (C- M, L- M and A- M figures) indicate that the upper Shidaling section is an aeolian deposit while the middle and lower Shidaling sections showing a typical positive dual- texture are fluvial deposits. Chronology and comparison with dating results of terrace reveal that the Shidaling section was formed between late middle- Pleistocene and late Pleistocene, the upper section formed at 110~60 ka BP. After correlation with the contemporaneously deposited sediments from the Yangtze River Basin, we propose that the upper Shidaling section is Xiashu Loess, and represents its western boundary. These results demonstrate that the Bingshubaojian Gorges is a division of the Xiashu loess and Wushan loess, which is similar to the loess in Chinese Loess Plateau. Geomorphologically speaking, the Bingshubaojian Gorges is a crucial area for studying regional climate and geo- environment and should receive more attention in future.