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    白垩纪:中国及邻区板块构造演化的一个重要变换期

    Cretaceous:A key transition period of the plate tectonic evolution in China and its adjacent areas

    • 摘要: 提要:中国及邻区是一系列不同起源的微大陆(克拉通)和地块经多期增生和碰撞而形成的复合大陆,海西—印支旋回和新特提斯旋回在其形成中起了决定性的作用。侏罗纪末白垩纪初部分新特提斯洋(有人称中特提斯)闭合,亚洲大陆的雏形出现,白垩纪末新特提斯洋全面消减,亚洲大陆形成,因而白垩纪是中国及邻区板块构造演化的一个重要变换期。笔者从地球动力学系统的变换、构造格局的变换、北东向新生构造的出现和造山作用类型的多样化等方面论述了这一变换。这一变换集中表现在中国及邻区的构造演化由原来的南、北分异在白垩纪转变为东、西两部发生分异,西部以构造的继承性为特色,东部则新生构造起了主要作用。反映在地形-地貌上,早白垩世该区东高西低,白垩纪末开始出现今日的西高东低面貌。盆地发育和“盆”“山”系统也在白垩纪开始发生重要变换,说明东亚大陆边缘因向太平洋的蠕散而不断解体,大陆内部构造则日趋复杂。中国及邻区的这一实例再次说明必须坚持活动论构造观,以动态演化的思路来重塑区域大地构造演化。

       

      Abstract: Abstract:The Asian continent (mainland China and its adjacent areas) is a composite one formed by multi-stage accretion and collision of a number of microcontinents (cratons) and blocks of different origins. The Hercynian-Indosinian cycle and Neo-Tethyan cycle played a decisive role in its formation. At the end of the Jurassic and the beginning of the Cretaceous, the Neo-Tethys ocean (which is called the Mid-Tethys by some people) closed and the embryonic Asian continent occurred. At the end of the Cretaceous, the Neo-Tethys ocean was consumed and the Asian continent originated;therefore the Cretaceous was an important transition period of the plate tectonic evolution of China and its adjacent areas. This paper discusses this transition in the contexts of the transitions of geodynamic system and tectonic framework, appearance of the NE-trending neogenic structures and diversity of orogeny. This transition is mainly manifested by the transformation of north-south differentiation to east-west differentiation in the region during the Cretaceous. The western part is characterized by the tectonic inheritance, while in the eastern part the neogenic structures played the main role. Geomorphologically, the region was high in the east and low in the west in the Early Cretaceous, while the present-day geomorphologic feature of being high in the west and low in the east began to appear at the end of the Cretaceous. The “basin-and-range” system also began to change significantly in the Cretaceous, which suggests that the margin of the East Asian continent was disintegrated progressively in response to its creep and dispersion toward the Pacific plate, and then the tectonics in the interior of the continent became increasingly complex. This case study further indicates that we must adhere in the tectonic concept of mobilism and reconstruct the regional tectonic evolution with the idea of dynamic evolution.

       

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