宜昌古老背晚更新世长江深槽研究—兼论长江深槽成因

Research on the Deep Trough of Late Pleistocene in Gulaobei, Yichang Area—A Discussion on the Causes of the Deep Troughs in the Great Three Gorges

摘要: 长江中游宜昌猇亭古老背一带发育晚更新世长江深槽，槽底深度位于现代海平面之下9米。古老背晚更新世长江深槽是在晚更新世全球气候变冷背景下，在长江束窄壅水、弯道环流泡水作用下，在上下游岩性软硬差异变化的基础上形成的。古老背晚更新世长江深槽后期的充填作用与晚更新世后期的海平面上升和全新世江汉盆地演化密切相关。对比研究表明，三峡中堡岛坝址区长江深槽与古老背晚更新世长江深槽在晚更新世不同阶段分别发生了长江深切、充填和再深切的阶段性变化特征，并具有同步演化的特点。研究表明，全球海平面变化引起的长江中游江汉–洞庭平原沉积基准面变化，改变了区内长江水动力条件，是长江深槽演变不可忽视的重要影响因素，甚至在距大海2000千米之遥的长江三峡地区。

Abstract: River Deep trough developed during the late Pleistocene in Gulaobei, Yichang area in the middle reaches of the Changjiang River, with the depth of the trough is located under the modern sea level for about 9 meters. The formation of deep trough is under the cold background of the global climate in the late Pleistocene, under the action of water in river constriction segment backwater and bend circulation, and on the basis of the variation of the lithology and hardness of the upper and lower reaches. The backfilling of the deep trough in the late Pleistocene is closely related to the sea level rise and the evolution of the Jianghan-Dongting Basin in Holocene. The comparative study shows that the deep trough of the Yangtze River in the dam site has the characteristics of synchronous evolution with the Gulaobei deep trough, while they have a deep and filling process at different stages of the late Pleistocene. The study shows that the change of sediment datum in the Jianghan-Dongting plain caused by the global sea level change has changed the hydrodynamic condition of Changjiang River in the middle reaches, which is an important factor that can not be ignored in the evolution of the deep trough of the Yangtze River, even in the Great Three gorges area, which is far away for about 2000 km.