三叠纪灰岩近东-西走向，层理清晰。在封闭体系环境中，地层受强烈构造挤压，被动作逆时针旋转（左旋），生成一组切穿地层的弧形断裂，成为帚状构造。其特征是：各断层向上端收敛，呈压性错断；向下端撒开，呈张性裂离。形成至今约2.5亿年。

   Triassic limestone is almost oriented east and west with clear bedding. This brush structure was formed in a closed environmentsystem, where formation underwent strong tectonic compression to rotate counterclockwise (left-hand), generating a set of cutting wear formation arc faults. This structure is characterized by the following: all faults are convergent to the top as compressional broken fault; spreading to the bottom in form of tensile crack. It has been formed for about 250 million years.