Growth and linkage of the Xiakou fault in the Linnan Sag, Jiyang Depression, Eastern China: Formation mechanism and sedimentation response

Abstract

Abstract Detailed geometric and kinematic analyses of a large multi-stage normal fault in the Jiyang Depression, eastern China, have been conducted using high-quality 3D seismic data. The Xiakou fault is a serrated fault zone consisting of four connected segments that alternately appear NE trending and EW trending. There are two tension stages, namely, the Ek stage (65 Ma) and Es4-Ed stage (50–23.5 Ma). The evolution process can be divided into four stages under the control of the regional geological background. In the Ek stage (65 Ma), only the NE-trending segments are active. The whole Xiakou fault zone is in the isolated fault growth stage. As the regional stress transformed from NW-SE to nearly S–N, the NE-trending segments in the Es4 stage (50 Ma) continued their activities and EW-trending faults started to develop. Soft connections were formed between the NE-trending segments. The Es3 stage (42 Ma) experienced intense SN-trending extension, and hard connections were formed in the Xiakou fault zone. The segmented faults in different directions became connected, forming a serrated fault zone that alternately appears NE-trending and EW-trending. Es2-Ed (38–23.5 Ma) is the stage of strike-slip transformation. Horsetail and strike-slip duplex structures developed in different positions. Local tension or extrusion of different fold segments occurred, which reflects the superposition effect of strike slip against an extension background. Hence, the spatial and temporal differences in the development and evolution of the Xiakou fault zone have important controlling effects on the distribution of the settlement depocentres and the source channels in this area.