摘要
通过详细的野外地质调查和精细的地震剖面构造解析,揭示了龙门山前陆褶皱冲断带的基本构造特征。对比分析了龙门山北段与南段构造变形几何学和运动学的差异,提出龙门山北段主要表现为一系列复杂的逆冲推覆构造,晚三叠纪变形强于新生代;龙门山南段则以基底卷入的叠瓦状冲断为特点,晚白垩纪—早第三纪变形尤为突出。与前陆褶皱冲断带相对应的是,川西晚三叠纪时期的周缘前陆盆地主要表现在整个龙门山褶皱冲断带的前渊地区;而晚白垩纪—早第三纪再生前陆盆地却局限在川西盆地的南部,并且印—藏碰撞的持续挤压作用使得晚新生代构造变形不断向东扩展进入川西盆地南部。
The Longmen Shan fold and thrust belt is a key region for the study of Meso-Cenozoic tectonic evolution of the China continent. This belt experienced at least two major tectonic events of the Late Triassic and Early Cenozoic ages, and formed obviously two phases of the foreland basin and the foreland fold-thrust belt. In this paper, the structural features of the Longmen Shan fold belt are presented, with both two-dimensional seismic profiles and field data. The complex structures of the NE-trending Longmen Shan fold-thrust belt and its foreland in the western Sichuan basin are interpreted as being formed by southeast-directed thrusting. The wedge-shaped Longmen Shan belt, consisting of numerous thrust sheets and nappes, thrust over the western side of the Yangtze craton. In both structural geometry and relative timing of folding and thrusting, the northern Longmen Shan is significant different from the southern Longmen Shan. The Longmen Shan fold and thrust belt can be divided into two major segments: the northern Long-men Shan and the southern Longmen Shan. Several eastward-verging, rootless thrust sheets and imbricates of the Cambrian-Triassic rocks have been recognized in the northern Longmen Shan. Evidence suggests that the northern Longmen Shan experienced two periods of major deformation in the late Triassic and Cenozoic ages, though the late Triassic deformation is more significant than the Cenozoic. Farther south, these principal tectonic units in the southern Longmen Shan are represented by the basement-involved thrust structures, and the frontal thrust structures propagated east-ward and actually passed from the edge of the thrust belt into the foreland of the western Sichuan basin. Its major deformation started in the Late Cretaceous-Early Cenozoic and continues to the present. Contemporaneous with thrusting was the development of the western Sichuan foreland basin. Sedimentary features of the foredeep exhibit two-phase flexural loading occurred within the western Sichuan basin, and suggest that the Late Triassic peripheral foreland basin extends along the foredeep of the Longmenshan belt, but the Late Cretaceous-Paleogene rejuvenated foreland basin is restricted in the southern part of the western Sichuan basin.
出处
《高校地质学报》
CAS
CSCD
2003年第3期402-410,共9页
Geological Journal of China Universities
基金
国家"十五"重点科技攻关项目(2001BA605A-06-01)
中国石油天然气集团公司创新基金
关键词
龙门山
褶皱冲断带
川西
前陆盆地
Longmen Shan
fold-thrust belt
foreland basin
western Sichuan
