长江中下游床沙组成垂直变化成因分析

通过晚更新世气候冷暖变化，分析长江河床演变，采用古地貌复原法，论证长江中下游床沙组成垂理变化成因。认为东中国海的海退和海浸，是形成长江中下游卵砾石潜伏于沙层之下，覆盖于基岩之上的原因；长江上游卵砾石推移质洲头，现在已运动到宜昌下游约１１０ｋｍ的江口一带。三峡工程投产后，因坝下游清水冲刷，卵砾石仍将向下游运动一段距离。

Analysis on the Causes of Vertical Variation of Bed Material in the Middle and Lower Reaches of the Yangttze River

Based on the river processes and the climate during the late Pleistocene, the formation of vertical variation of the bedmaterial in the middle and lower reaches of the Yangtze River is analyzed through the rehabilitation of the ancient landform. The marine invasion and regression of the east sea of China are the causes to the phenomena that the gravel is below the sand and on the foundation stone. The gravel bedload progress in the Yangtze River is near Jiangkou, 110 kilometers down from Yichang city. After the construction of the Three Georges Project, the progress would go on.