STRUCTURAL GEOLOGY OF DABA SHAN FTB AND ITS TECTONIC SIGNIFICANCE, CENTRAL CHINA

Daba Shan is a fold-and-thrust belt located on the northeastern margin of the Sichuan Basin, central China orogen. It is the transitional zone between the Sichuan Basin and Qinling orogenic belt, and it is located in the middle part of the Mianlu suture zone which is the boundary between the Qinling orogenic belt and Yangtze block. Numerous faults and fault-related folds are well preserved in Daba Shan. It is a natural laboratory to carry out fold-thrust belt research on relationships between the Qingling orogen and subsidence in the Sichuan basin. In this talk, I will introduce the general geologic background about and around Daba Shan, including the geologic history of the central China orogen, the formation and development of the Mianlue suture, and the most popular ideas about the geodynamic evolution of Daba Shan, as well as its geologic position between the Sichuan Basin and North China craton and its relative geodynamic relationship with Mianlue suture zone. Field investigations have shown the different fault-related structure styles, e.g. fault-bend fold, fault-propagation fold, duplex structure across the orogen. In addition, a major extensional detachment fault, the Chengkou fault, crops out in the center of the orogen and dips beneath northern Daba Shan fold-thrust belt and Mianlue suture. It is so impressive of the typical and complex geological structure scenarios there, which were mostly caused by the collisional and post-collisional activities between Qinling micro-continent and Yangtze block since mid-Triassic time. Daba Shan has very important tectonic and economic significance in China. These years, with gas and oil exploration development in foreland basin and fold-thrust belt areas, especially after the discovery of carbonate strata in Daba Shan, its economic potential has become more prominent. For the further research, I will complete construction of balanced cross-sections, calculation of the shortening amount, and determine the timing of the faulting in Daba Shan with the interpretation of seismic-reflection profiles interpretation and remote sensing images to better understand the geologic structures of Daba Shan. This research will be significant for geoscientists to better understand the geologic features of Daba Shan.