近五千年来长江中下游干流的演变

THE EVOLUTION OF THE MID-LOWER CHANGJIANG RIVFR IN THE LAST 5000 YEARS

主要根据河漫滩相沉积的加积过程与厚度变化,埋藏古树层及埋藏古文化层的分析,发现近五千年来长江中下游干流洪水位上升了大约20m,并发展了曲流、洲滩、分流,以及支流河口成为自然堤后湖的变化.造成上述种种变化的主要原因是气候变化、海面运动、泥沙淤积、构造运动及人为活动的影响等,估计今后,所述种种变化还会继续发展下去.

Mainly based on studies of the aggrading process of the flood-plain, its change in thickness, the buried palcoforcst, and the buried ancient cultural layer etc., it is discovered that the flood stage rose about 20 m. in the last 5000 years. A large number of meanders, sand bars, flood plains, disribulary and lateral level lakes also formed at the same lime. Some of these phenomena arc due to climatic change, sca-lcvcl fluctuation, aggradation of a great quantity of mud and sand on the river bed and flood plain, erustal movement and influence of man-made work etc Finally, it is estimated that these changes in the Mid-lower Changjiang Valley would continuously develop at in a slow rate in future.