北京西山河北庄地区层内褶皱的构造分析

通常发育在变质岩系中的层内褶皱近年来在北京西山的沉积岩层中广为发现。其特征表明,它们系构造成因,而非同沉积褶皱。通过层内褶皱的构造分析,尤其是它与大型褶皱特殊关系的查明,以及变形标志体的有限应变分析,北京西山的层内褶皱是大型纵弯背斜之上重力垂向压缩及侧向扩展的产物。

A STRUCTURAL ANALYSIS ON INTRAFOLIAL FOLDS IN HEBEIZHUANG AREA OF BEIJING WESTERN HILLS

Intrafollal folds which are normally developed in metamorphic rocks have recently been widely discov-sred in Upper Proterozoic and Lower Paleozoic sedimentary rocks at Beijing Western Hills. A series ofcharacteristics show that these intrafolial folds are not contemporaneous sedimentary structure but of tec-tonic origin. On the basis of structural analysis and the study of their specific relationship with macroscopic folds,these intrafolial folds are believed to have formed through the vertical compression and the lateral exten-sion on a large longitudinal bended anticline under gravitation after the Indo-China Movement. This inter-pretation is supported by the finite strain analysis in this area,