TRACE PATTERN AND GROWTH PROCESS OF YUJIANG THRUST BORDERING EAST SICHUAN AND WEST HUBEI
Wu Shuren1, Chen Qingxuan1, Hu Daogong1, Wu Ganguo2, Xu Ruichun3, Mei Yingtang3, Yi Shunhua4, Wang Huabin
1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081; 2. China University of Geosciences, Beijing 100083; 3. Survey Institute of the Three Gorges, the Yangtze River Water Conservancy Commission, Yichang 443003; 4. China University of Gosciences, Wuhan 430074
The trace pattern of the Yujiang thrust bordering east Sichuan and west Hubei is measured from the geological investigation over the past five years. The trace pattern is characterized by the segmentation, zonation and the frontal imbricate thrust structure with overstep propagation. Of them, the zonation is divided into a frontal imbricate thrust sub-zone with the low angle and a back normal fault sub-zone with the high angle. The imbricate thrust zone, displaying overstep propagation, derived from the flat and the ramp changes of floor thrust, especially secondary fracturing branches along the ramp direction. The frontal thrust displays thrust movement from NW toward SE with the displacement of 10 m to 100 m-scale, and the largest displacement is less than 1 km. The displacement of the back normal fault is in line with one of the frontal thrust. The trace pattern of the Yujiang thrust was formed in the Yanshanian movement (Late Jurassic-Early Cretaceous), and the growth process of the trace pattern displays the branch faults growth from the frontal toward back along the ramp direction of the floor thrust. The back normal faults derived from the feedback relations of the trace pattern, movement accommodation and self-organization in the Yujiang thrust zone, and the Himalayan orogeny enhanced the growth and development of the normal fault.