关键词: 长江, 古河谷, 末次冰期, 低海面

Abstract: Numerous boreholes demonstrate that there is indeed an incised paleo-valley stretching into the East China Sea from Zhenjiang and Yangzhou at the apical area of the Changjiang Delta. The filling deposits in the paleo-valley are of fluvial. neritic and deltaic facies. The fluvial sedimentary unit composed of sand with gravels and sand at the low part, and of grey sandy clay with sandy lenses at the upper part, is a fining-upward sequence with erosional boundary at its bottom. The unit was formed by retrogressive aggradation in process of the postglacial transgression. The 14C datings show that the fluvial unit was deposited during the postglacial period while the sea level rised rapidly and the paleo-valley was incised when the sea level lowly standed. The fluvial facies is overlain by the neritic facies which consists of grey mud rich in marine microfossils-.The deltaic facies including mouth bar sand and distributary sandy clay covers the neritic facies nearly in the limits of the paleo-valley. The presence of enormous paleo-valleys support that the Changjiang River was still sea-running during the period of sea lowstand in the last giaciation.

Key words: Changjiang River, paleo-valey, last glaciation, sea level lowstand