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5.12汶川大地震是在无任何征兆的情况下发生的,这表明龙门山构造带现今的应力与应变场以及在历史中形成的构造格架极为复杂.龙门山构造格架先是形成于太平洋和特提斯两大构造域在中生代的相互作用,后又作为青藏高原的东边界协调青藏高原的隆升和水平生长,其现今的地质地貌格局就形成于这两构造事件的叠加作用.在晚三叠世,扬子西缘发生陆内汇聚作用,在川西形成龙门山构造带,并导致四川前陆盆地的形成,龙门山与四川前陆盆地表现出典型的盆山耦合关系.然而,在中生代大部分时间里,松潘-甘孜构造带与扬子地块表现出截然不同的造山极性.扬子地块沿一系列左行走滑断裂持续发生顺时针旋转,并主要在四川盆地发育一套河湖相沉积,而松潘-甘孜构造带则以大规模北东-南西向挤压缩短为特征,并发生整体抬升.在新生代大部分时间里,龙门山和四川盆地对青藏高原的生长和抬升并没有表现出强烈的构造和沉积响应.在地壳表面水平变形速率很低的背景下,现今的龙门山却呈现出非常年轻的高峻地貌特征,其地形梯度之大甚至超过喜马拉雅山.由此可以推测青藏高原与四川盆地之间的汇聚作用可能发生在地壳深部,可能受下地壳流动的控制.晚新生代时期发源于青藏高原东缘的岷江在龙门山山前突然卸载了大量的洪积物,充填在成都平原内,是气候还是构造成因?对此存在不同的认识.汶川大地震引发了大面积的滑坡、泥石流和河流的堰塞,这些地质灾害给我们的启示是:成都平原的砾石沉积可能有相当一部分与地质历史中大地震引发的洪水有关,其中最著名的是大邑砾岩.在大邑砾岩之下还存在一套沉积特征截然不同的砾岩,其年龄可能是晚中新世(8~13Ma),这些砾岩连同上覆的大邑砾岩和下伏的中生界岩层沿安县-灌县断裂发生了强烈的褶皱,由此可以厘定青藏高原东缘大规模隆升机制和时间.
The 5.12 Wenchuan earthquake occurred without any indication, indicating that the present stress and strain fields in the Longmen Shan tectonic belt and the tectonic framework formed in history are extremely complicated. The Longmen Shan tectonic framework first formed in the Pacific Ocean and Te Teth’s interaction between the two tectonic domains in the Mesozoic, and later as the eastern boundary of the Qinghai-Tibet Plateau to coordinate the uplift and horizontal growth of the Qinghai-Tibet Plateau, the current geology and geomorphology formed in the superposition of these two tectonic events in the late three During the stratigraphy, intracontinental convergence took place in the western margin of the Yangtze River, forming the Longmen Shan tectonic belt in the western Sichuan and leading to the formation of the Sichuan foreland basin, and the Longmenshan and Sichuan foreland basins showed a typical basin-mountain coupling relationship. However, The Songpan-Garzê tectonic belt and the Yangtze block show quite different orogeny polarities in the time.The Yangtze block continues to rotate clockwise along a series of left-lateral strike-slip faults and develops a set of river and lacustrine deposits mainly in the Sichuan Basin, While the Songpan-Garzê structural belt is characterized by a large North-East-Southwesterly crushing and shortening, and the whole uplift occurs. During most of the Cenozoic era, the Longmenshan and Sichuan basins No strong tectonic and sedimentary response to the growth and uplift of the Tibetan Plateau.At present, under the background of the low horizontal deformation rate on the surface of the crust, today’s Longmen Mountain is characterized by very young and severe landform with large gradient Even beyond the Himalayas.Thus it can be speculated that the convergence between the Qinghai-Tibet Plateau and the Sichuan Basin may occur in the deep crust, may be controlled by the lower crustal flow.The Late Paleozoic originated in the eastern edge of the Qinghai-Tibet Plateau in front of the Longmenshan piedmont Suddenly, a large amount of sediments have been unloaded and filled in the Chengdu Plain, so climate or structural causes have different understandings. The Wenchuan earthquake triggered a large area of landslides, landslides and river weirs, which have given us The revelation is that a considerable part of the gravel deposits in the Chengdu Plain may be related to the floods caused by the earthquake in the geological history, the most famous of which is the Dayi conglomerate, and there is also a set of distinct depositional features under the Dayi conglomerate The conglomerate, which may be of late Miocene age (8 ~ 13 Ma), these conglomerates along with overlying Dayi conglomerate and the underlying Mesozoic strata along Anxian- County fold rupture occurred intense, which can determine the eastern Qinghai-Tibet Plateau uplift mechanism and time.