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成都盆地位于青藏高原东缘,夹于龙门山与龙泉山之间,盆地的长轴方向平行于龙门山,呈现为北东—南西向展布的线性盆地。盆地中充填了3.6Ma以来的半固结—松散堆积物,最大厚度为541m,在垂向上由下部的大邑砾岩、中部的雅安砾石层和上部的上更新统至全新统砾石层组成,其与下覆地层均为不整合接触,显示该盆地是一个单独的成盆期,并非是在中生代前陆盆地基础上形成的继承性盆地。在垂直于龙门山造山带方向上,成都盆地具不对称的楔形结构,沉积基底面整体向西呈阶梯状倾斜,盆地中充填的碎屑物质均来源于盆地西侧的龙门山,具横向水系和单向充填的特征;而且盆地的沉降中心具有逐渐向远离造山带方向迁移的特征,显示盆地的挤压方向垂直于龙门山主断裂,造成了成都盆地在垂直于造山带方向上的构造缩短。在平行于龙门山造山带方向上,成都盆地具有一系列的北东向延伸的次级凸起和凹陷,凹陷和凸起相间分布,且在空间上呈斜列形式展布于盆地的底部,其中次级凹陷(沉降中心)和冲积扇具有向平行龙门山造山带方向迁移的特征,表明成都盆地西缘的龙门山断裂具有右旋走滑的特征。鉴于以上特征,认为成都盆地是在龙门山造山带晚新生代走滑与逆冲的联合作用下形成的走滑挤压盆地。
Located in the eastern margin of the Qinghai-Tibet Plateau, the Chengdu Basin is sandwiched between Longmenshan and Longquanshan. The long axis of the basin is parallel to Longmen Mountain, presenting a linear basin distributed in the NE-NW direction. The basin is filled with semi-consolidated and unconsolidated sediments since 3.6 Ma, with a maximum thickness of 541 m. It is composed of the Lower Daying conglomerate in the lower part, the Ya’an gravel layer in the middle part and the Upper Pleistocene to Holocene gravel layer in the vertical direction, They are all unconformities with the overlying strata, indicating that the basin is a separate basin and not a succession of basins formed on the basis of the Mesozoic foreland basin. In the direction perpendicular to the Longmen orogenic belt, the Chengdu basin has an asymmetric wedge-shaped structure. The sedimentary basement surface is steeply inclined to the west as a whole. The clastic materials filled in the basin originate from the Longmen Mountain on the west side of the basin and have horizontal water systems And the characteristics of one-way filling. Moreover, the subsidence center of the basin has the feature of migrating gradually away from the orogenic belt, indicating that the direction of extrusion in the basin is perpendicular to the main fault of the Longmen Shan, resulting in the shortening of the structure of the Chengdu basin in the direction perpendicular to the orogenic belt . In the direction parallel to the Longmen orogenic belt, the Chengdu basin has a series of northerly extending secondary bumps and dimples, with dimples and bumps distributed in phases and spatially arranged obliquely on the bottom of the basin, The secondary depressions (sedimentation centers) and alluvial fans have the characteristics of migrating parallel to the Longmenshan orogenic belt, indicating that the Longmenshan fault in the western margin of the Chengdu basin has a dextral strike-slip feature. In view of the above characteristics, it is considered that the Chengdu basin was a strike-slip compression basin formed by the combined effect of Late Cenozoic strike-slip and thrusting of the Longmen orogen.