| 龙门山南段前陆区晚第四纪构造变形样式 |
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| 引用本文： | 姜大伟,张世民,李伟,丁锐.龙门山南段前陆区晚第四纪构造变形样式[J].地球物理学报,2018,61(5):1949-1969. |
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| 作者姓名： | 姜大伟 张世民 李伟 丁锐 |
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| 作者单位： | 中国地震局地壳应力研究所, 地壳动力学重点实验室, 北京 100085 |
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| 基金项目： | 国家自然科学基金（41272234）和中国地震局地壳应力研究所中央级公益性科研院所基本科研业务专项（ZDJ2017-24）共同资助. |
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| 摘 要： | 龙门山中南段前陆区是青藏高原东缘唯一发育新生代薄皮构造与沉积盆地的地段，研究其最新构造变形样式有助于深入理解青藏高原向东扩展的构造机理.论文通过青衣江河流阶地测量与古青衣江洪积扇形态重建，研究了龙门山南段前陆区晚第四纪活动构造格局及其活动性，取得了如下认识：（1）青衣江河流阶地纵剖面显示，龙门山南段前陆地区晚第四纪变形主要为褶皱作用，总体地壳缩短速率为2.5~3.9 mm·a-1，远大于山区冲断带0.48~0.77 mm·a-1的地壳缩短速率，地壳缩短主要由前陆地区吸收；（2）青衣江古洪积扇错断变形显示，龙门山南段前陆区活动构造表现为北西—南东向地壳缩短与近东西向的地壳缩短的叠加作用，两者分别受控于巴颜喀拉块体南东向推挤作用与川滇块体向东推挤作用；（3）自中新世初川滇块体向南东挤出，四川盆地西南角起到分流青藏高原物质的作用，其西南侧物质通过鲜水河—小江断裂带的左旋错动向南东方向分流，其西北侧物质通过龙门山断裂带的右旋错动向北东方向分流，迎面受到了最大的推挤作用，进而向前陆扩展形成了薄皮褶皱构造带.
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| 关 键 词： | 龙门山南段 前陆盆地 青衣江 变形样式 |
| 收稿时间： | 2018-04-18 |
Foreland deformation pattern of the southern Longmen Shan in Late Quaternary |
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| JIANG DaWei,ZHANG ShiMin,LI Wei,DING Rui.Foreland deformation pattern of the southern Longmen Shan in Late Quaternary[J].Chinese Journal of Geophysics,2018,61(5):1949-1969. |
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| Authors: | JIANG DaWei ZHANG ShiMin LI Wei DING Rui |
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| Institution: | Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China |
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| Abstract: | The foreland of the south-central Longmen Shan is the only area which hosts Cenozoic thin-skinned structures and sedimentary basins in the eastern margin of the Tibetan Plateau. Studying the latest tectonic deformation patterns can help us to understand the mechanism of the eastward expansion of the Tibetan Plateau. This paper focuses on the foreland of the southern section of the Longmen Shan.Through the surveys to the Qingyijiang River terraces and the ancient Qingyi River alluvial fans, we have studied the tectonic pattern and the Late Quaternary deformation in this region. The results show that (1) the longitudinal profile of the Qingyijiang River terraces indicates that the Late Quaternary deformation in the foreland of the southern Longmen Shan was mainly a folding process, and the overall crust shortening rate was 2.5~3.9 mm·a-1, much larger than the 0.48~0.77 mm·a-1 of the mountainous thrust zone. Therefore, the shortening of the crust in the southern section of the Longmen Shan was mainly absorbed by the foreland region. (2) The deformation of the ancient alluvial fans of the Qingyijiang River shows that there were two N-S striking thrust faults in the foreland superimposed upon the SW-NE striking anticlines and thrust faults. It suggest the NW-SE shortening was controlled by the southeastward push of the Bayan Hark block, and the E-W shortening was characterized by the eastward push of the Sichuan-Yunnan block. (3) The extrusion of Sichuan-Yunan block may play a key role in controlling the formation of foreland thin-skinned fold structure in the south-central segment of the Longmen Shan. Since the Miocene when Sichuan-Yunnan block was extruded to the southeast, the southwestern corner of the Sichuan Basin acted as a diversion wedge for motion of the Tibetan Plateau. The southwestern side was diverted southwestwards through the left-lateral slip of the Xianshuihe-Xiaojiang faults zone. The northwest side was diverted to northeastwards through the right-lateral slip of the Longmen Shan faults zone. Accordingly the corner suffered the strongest head-on pushing, and crustal shortening was accommodated by thrust faulting and foreland folding. In addition, under such a structural load, the Chengdu sedimentary basin was formed. |
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| Keywords: | Southern Longmen Shan Foreland basin Qingyijiang River Deformation pattern |
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