TECTONIC DEFORMATION CHARACTERISTICS OF THE SOUTH DABA TECTONIC BELT DURING MESOZOIC AND CENOZOIC

Compressed from both Qinling and Xuefeng directions,the South Daba Tectonic Belt,known as a typical thrust and fold belt,has experienced long history of development ever since the Indo-Chinese period.The composite stress displays a clockwise movement during the early stage and an anticlockwise movement during the late stage respectively.Because of the time and spatial changes in stress direction and the existence of multiple layers of detachment,deformations during Mesozoic and Cenozoic are cha-racterized by multiple phases,multiple directions,multiple layers and multiple phases'composition.The tectonic deformations include gentle fold(late Indo-Chinese),fold generation(early Yanshanian),thrust and fold(middle Yanshanian),thrust(early Himala-yan) and uplift and erosion(late Himala-yan).The major compression comes from Qinling and the minor from Xuefeng Mountain as well as Micang and Longmen Mountains.Tectonic deformations during Mesozoic and Cenozoic are controlled by either simultaneous or un-simultaneous composite actions.Due to the southward shoaling of stress in its transfer process and the existence of plastic layers,the deformation exhibits a vertical and planar pattern of multiple layers.Influenced by the multiple originated and multiple directional compression simultaneously or un-simultaneously,the deformation in this area is both complicated and complex.