博格达山北缘前陆褶皱冲断带构造特征及其动力学意义

The structural characteristics along the northern piedmont of Bogedashan and its dynamic significances

博格达山北麓褶皱逆冲带是现代地质学研究的一个热点,但是大部分的研究都集中于古生代和新生代的构造变形,对于中生代多期构造变形少有关注。本文通过野外地质观测和卫星照片解析,结合前人地震剖面,识别出中生代以来博格达山北麓褶皱逆冲带内3期不同的构造变形:1)是由于印度—欧亚板块碰撞远程效应所引起的新生代逆冲推覆构造,表现为一系列逆冲断层及相关的褶皱;2)是侏罗纪末—白垩纪初博格达山遭受挤压变形,在山前形成宽缓的褶皱;3)是博格达三叠纪末—侏罗纪初的构造变形,可能对应于博格达山的初始隆起,这期构造变形表现为博格达山北麓上二叠统的强烈褶皱变形。这些结果表明博格达山的隆升具有多期次的特点,主要受亚洲板块南缘不同时期小陆块碰撞的控制。

The fold-and-thrust belt of the northern piedmont along Bogdashan is a hot spot of modern geological study. The most previous studies focused on the Paleozoic and Cenozoic structural deformations. However, few studies concerned its Mesozoic multi-phases deformations. This study distinguished three phase of deformation since Mesozoic along the northern piedmont of the Bogdashan, based on carefully structural observation in field, image satellite and previous published seismic profiles. The first one is the Cenozoic thrust structure and related folds, which is caused by the far-effect of the India-Eurasia collision. The second deformation is characterized by the wide wave-length folds during the boundary between the Late Jurassic and the Early Cretaceous. The third deformational phase probably related to the inception of the uplifting of Bogdashan. It shows intensive deformation within the Upper Permian. These results suggest that Bogdashan has the characteristics of multi-phase uplifting, mainly caused by the collisions of different small blocks at the southern edge of Asia.