大河的地质演化与构造控制

GEOLOGICAL EVOLUTION OF BIG RIVER SYSTEMS AND TECTONIC CONTROL

基于对全球60条主要的河流(欧亚大陆35条,美洲15条,非洲8条,澳大利亚2条)的综合分析,介绍了大河的地质演化及其构造控制作用。研究表明,大河流系的地质特征和起源受控于4个因素:板块构造、气候、火山作用和相对基准面的变化。其中,最重要的因素是板块构造,它决定了大河的位置、大小、形状、流向、生命周期及水系的样式。宽泛地讲,大河系统的形成和演化与威尔逊旋回密切相关,因此,大河的生命周期和全球地形的演化,都与构造旋回有相同的时间尺度。冈瓦纳大陆的裂解以及特提斯洋的闭合,对于欧亚大陆水系样式的形成起到了决定性的作用。在欧亚大陆,注入北冰洋的河流和注入太平洋、印度洋的河流的分水岭与冈瓦纳大陆的北部边缘密切相关。在南美洲和北美洲,是洋-陆板块汇聚以及科迪勒拉-安第斯造山带微陆块的增生决定了美洲大陆主要水系的样式。大河能够长期存在的关键因素在于它要位于克拉通或被动大陆边缘这样的构造相对稳定地区,要有长期存在的大陆倾斜地形,而且流域内不曾发生过荒漠化、大陆冰川作用或火山作用。

Based on the characteristics of 60 major big river systems worldwide ,55 in Eurasia, 15 in the Americans, and 2 in Australia, the paper focuses on the geological evolution of the big river systems and their tectonic control. In general ,four major factors are important in terms of river evolution： tectonics, climate, volcanism and base level changes. Plate tectonics is the most important single factor, which determines the location and evolution of a big river system. Climate and base level changes, under extreme circumstances, are also important. Volcanism played more important roles in the Earth＇s early history. In general, the born and evolution of a big river system results largely from the Wilson cycle of initial hot spot→dome→continental rift→birth of the sea-→small ocean→large ocean and passive margin→ small and closing ocean with active margin→new direction of continental tilt and drainage asymmetry. As a result,big river system operates on the same time scale as tectonic cycles. The drainage pattern in Eurasia is the daughter of the breakup of Gondwana in the Late Permian and the closing of the Tethyan Ocean in the Early Cenozoic. The two big sutures across the Eurasia from west to east constrain the location of big rivers draining through the continental ,for example the divide between north flowing rivers to the Arctic Ocean and rivers flowing to the Pacific and Indian Oceans closely follows the northern limits of Gondwana. The radial drainage pattern in East Asia and South Asia is the result of the closing of the Tethyan Ocean and the uplift of Tibet Plateau. In the Americans, ocean-continent convergence and accretion of microcontinents to the Cordilleran and Andean orogens are responsible for much of the major drainage pattern of the continents. Based on the comprehensive analysis and correlation among big river systems worldwide,we find that the key to the long-term survival of a large river is locating on a long-lived craton or passive margin and persistence of continental tilt,with no desertification, continental glaciation or volcanism. The history of both the Yangtze and Yellow Rivers in China are relatively young, owing to the fact that the uplift of Tibet Plateau occurred during Cenozoic.