Construction and structural analysis of regional geological sections of the southern Daba Shan thrust-fold belts

The Daba Shan thrust belt has very complex structures, and could be divided into two parts by the Chengkou-Fangxian fault. The north part (North Daba Shan) is regarded as the conjunction between the South Qinling Orogen and the Upper Yangtze block, while the south part (the South Daba Shan) is a typical thrust-fold belt. In this paper, we focus on the structures of the South Daba Shan thrust-fold belt. The result indicates that it has multi-level and multi-stages deformation. The upper system is controlled by detachment along the gypsum layers in the limestone of the lower Triassic Jialingjiang Formation, and nearly all the Mesozoic strata are involved into the deformation. While the lower system is confined between two detachment surfaces: The gypsum layers in the lower Triassic Jialingjiang Formation and the shale in the Sinian. We accomplish three comprehensive regional geological sections, as well as their balance restoration sections, across the South Daba Shan based on geophysical data and field investigation. According to them, we study in detail the structure and distribution of the upper and the lower thrust systems, their geometric and kinematic characteristics, and the spatial relationship between the Daba Shan and the Chuandong thrust-fold belts. We conclude that the South Daba Shan thrust belt is a complex multi-level thin-skinned thrust system with strong deformation and shortening.