嘉陵江古河曲发育的古地理环境重建
The reconstruction of paleogeographic environment for the development of the Jialing River’s ancient meander
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摘要: 提要：嘉陵江古河道的遥感影像轮廓反映了自由河曲的河流形态信息，分析嘉陵江古河曲的发育条件对其区域古地理环境的重建和恢复具有重要的地貌学研究意义。本文在综合前人关于自由河曲的理论与实际案例研究成果的基础上，总结了自由河曲的发育条件。据此，结合野外调查资料，认为嘉陵江古河曲形成时，该区应为平坦开阔的冲积平原，河流纵比降较比现在更小；河流两岸为具有“二元结构”的松散沉积物。与长江下荆江河段的地理环境类似。且“三水汇流”（嘉陵江与渠江、涪江）格局已经存在。嘉陵江由自由河曲转为深切河曲是由于区域地质环境（或地质事件）的改变所引起的。Abstract: 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.
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