The reconstruction of paleogeographic environment for the development of the Jialing River’s ancient meander

Abstract：Remote sensing images of the Jialing River’s old channel reflect the river pattern information of the free meanders. The analysis of the development condition of the old meanders of the Jialing River has important geomorphological significance in the reconstruction and restoration of the regional paleogeographic environment. On the basis of previous researches and practical cases on the free meanders, this paper summarized development conditions of the free meander. On such a basis, in combination with field investigation data, the authors hold that, when the ancient meander stared its formation, the area was a flat and wide plain landform, and the channel gradient ratio was smaller than the present value. Materials of banks on both sides of the river were composed of unconsolidated sediments characterized by “dualistic structure ”. This geographical environment was similar to the that of the lower part of the Jingjiang River that belonged to the Yangtze River. Moreover, the pattern of “ three confluence rivers ” composed of the main stream of the Jialing River and its tributary ( Qujiang River and Fujiang River ) had already existed at that time. The transformation of the free meander to the incised meander of the Jialing River was caused by change of the regional geological environment or the geological events.