Abstract: The Sudong syncline is shaped like an asymmetric dumbbell. This special shape stands out on geological map and makes its genesis worthy of investigation. Based on the analysis of regional tectonic evolution background and the structural analysis of Sudong syncline, we discuss the genesis of Sudong syncline, which is further verified by combining the tectonic development characteristics of Zhuxianzhuang Coal Mine. The results show that the Sudong syncline can be divided into four deformation zones including NE limb integral deformation zone, SW limb extrusion deformation zone, SW limb extrusion deformation zone and SW limb normal deformation zone. Sudong syncline formation involved two key deformation stages. that is, deformation under the continuous SW directed compression: a Sudong Syncline characterized by interlayer bending adjustment and“X”conjugated fracture formation period (Extrusion bending stage), and the trending of strip of the southeast Sunan box syncline with the“X”type conjugate fracture translation characterized by intrusion and extrusion period (Trending Translation stage). The Coal vitrinite reflectance indicatrix in the 8# coal seam of Zhuxianzhuang Coal Mine records the direction of stress in each stage of syncline formation. The regular distribution of bedding slip in different deformation types and degrees of the 8# coal seam is a good response to the formation mechanism of“trending extrusion bending slip-trending translation”in Sudong syncline. We propose a method for calculating the along-strike fault offset which is based on the contour of coal seam floor. Using this method, the translation direction and offset of the fault in the southern Zhuxianzhuang Coal Mine were quantitatively characterized and the mechanism of the trending translation of the Sudong syncline was further verified.

Key words: Xuzhou-Suxian arc structure belt, Sudong Syncline, structural assemblage, trending extrusion bending slip, trending
translation, tectonic formation mechanism