FEATURES AND GENETIC MECHANISM OF FAULTS IN THE SUN BASIN IN MESOZOIC AND CENOZOIC TIMES

The sun basin is located in the east of the North Yellow Sea basin, a lowly explored Mesozoic-Cenozoic sedimentary basin, which is developed upon the base of China-Korea paraplatform. The latest 2D seismic data indicated that the fault system of the Sun basin can be divided into 5 types:basin-controlling faults, depression-controlling faults, belt-controlling faults, trap-controlling faults and segmentation faults, which dominantly trend northeast or northwest, and only a few faults trend north to west or north to south. The analyses on these faults indicate that the fault activities can be mainly divided into four stages:late Jurassic-early Cretaceous,late Cretaceous,Eocene and Neogene. Since Mesozoic and Cenozoic, the tectonic evolution of east China has mainly been controlled by the activities of the Pacific plate. In the late Jurassic, going with the subduction of the Pacific Ocean-Philippines Sea plate, the oceanic crust subducted under the Eurasia plate, and the Sun basin experienced NNE-SSW-trending extension under the background. In the early Cretaceous, due to the change of subduction direction of Pacific plate, the regional NNW-SSE extension turned to the regional NNW-SSE compression, and a series of NW-trending thrust faults were formed asaresult. In the Eocene. the Sun basin had extension again, which was the result of the slowdown subduction of the Pacific plate towards East Asian mainland. At the end of Oligoeene,influenced by Himalayan movement, the Sun basin became reversed again, and a series of small faults formed.