动力地形控制下的大河水系演化

Large River Drainage System Evolution under Dynamic Topography

大河既是人类文明的发源地,也是大陆地貌乃至地球表层系统中最重要的组成部分。大河水系形成与演化的决定性因素是大陆构造演化引起地形的改变。传统观念认为,大河水系的演化主要受板块构造的影响即“构造地形”,但越来越多的证据表明,地球地形并非单纯由板块水平运动塑造,还包括由地幔对流造成的“动力地形”的影响。从深部地幔对流控制下的动力地形与地貌演化模型两方面,分别介绍了其概念,模拟计算以及模型验证。并以北美、澳大利亚、南美以及非洲的大河水系演化为例,阐明了大河水系的演化与长波长动力地形之间存在的耦合关系,相对于构造作用的局部影响,长波长动力地形能影响甚至改变大陆尺度上的水系演化模式。最后简要综述了亚洲的构造背景及动力地形研究进展,亚洲特别是东亚地区从侏罗世开始就受到了多阶段板块汇聚与俯冲的影响,动力地形情况复杂,但最近的研究表明东亚地区的水系演化与动力地形之间存在相应联系,这对亚洲地区的构造—沉积演化研究具有重要的指示意义。

Large rivers are not only the birthplace of human civilization,but also the most important part of the land⁃scape and the surface system of the earth.The decisive factor of the formation and evolution of large river drainage sys⁃tems is the topography change caused by continental tectonic evolution.Traditionally,it is believed that the evolution of large river drainage systems is mainly influenced by plate tectonics,which is called“tectonic topography”.Howev⁃er,more and more evidence shows that the earth’s topography is not only shaped by horizontal plate movement,but also by the influence of“dynamic topography”caused by mantle convection.This paper introduces the concept,simu⁃lation calculation,and model verification of dynamic topography under the control of deep mantle convection and landscape evolution models.Taking large river drainage system evolutions in North America,Australia,South Ameri⁃ca,and Africa as examples,we conclude that there is a coupling relationship between the evolution of large river drainage systems and long-wavelength dynamic topography.Compared with the local influence of tectonic movement,the long-wavelength dynamic topography can influence and even change the evolution pattern of drainage systems on the continental scale.Finally,the tectonic setting and dynamic topography of Asia are briefly reviewed.Asia,espe⁃cially East Asia,has been affected by multi-stage plate convergence and subduction since the Jurassic;therefore,the dynamic topography is complex.However,recent studies show that there is a corresponding relationship between the evolution of drainage systems in East Asia and the dynamic topography.This is of great significance for subse⁃quent tectonic-sedimentary research in Asia.