Tectonic deformation and evolution of the South Yellow Sea basin since Indosinian movement

Tectonic deformation of the South Yellow Sea basin since the Indosinian tectonic movement is studied in this paper based on the seismic data over the past years and the correlation between the sea and land areas of the Lower Yangtze platform. There are three stages of tectonic deformation in the South Yellow Sea since the Indosinian. The first stage from late Indosinian to early Yanshanian is dominated by foreland deformation including both the uplifting and subsidence under an intensive compression environment. The second stage which is called the Huangqiao Event in the middle Yanshanian, is dominated by transform deformation, suggesting a change of stress field from extrusion to extension. In the third stage or the Sanduo Event in the late Himalayan, however, the deformation was changed from the late Cretaceous-Paleogene stretching rifting to the Neogene-Quaternary depression. During the process, it controlled 3 stages basin formation from a foreland to fault and depression basin. In conclusion, since the Indosinian, the South Yellow Sea basin has experienced deformations of compressional folding and faulting, collisional mountain-building, compressional and tensional pulsation, strike-slipping, block extension and inversion, compression and convergence. Structures in NE, NEE, nearly EW and NW directions coexist. From west to east, they change directions from NEE to near EW to NW, while from north to south they change from NEE to near EW in a zonal pattern from strong to weak to strong. Vertically, the marine and terrestrial basins alternate in a "seesaw" pattern with fold thrusts in early stage, which is stronger in north and weaker in south and extension rifts in later stage, which is stronger in north and weaker in south. In marine basins, stronger thrusting deformation is more popupar in upper structural layer than that in the lower layer. The tectonic deformation mechanism in the South Yellow Sea basin is mainly affected by the drift collision between the Yangtze and North China blocks, and the stress environment of large-scale strike-slip faults owing to activities of the Paleo-Pacific plate. The southern part of the Laoshan uplift is a weak deformation zone as well as a stress release zone, and the Meso-Paleozoic reform is weak in later stage. It is believed, therefore, a favorable area for oil and gas exploration.