TECTONIC CHARACTERISTICS AND EVOLUTION OF THE WEST DEPRESSION BELT OF THE EAST CHINA SEA SHELF BASIN

Based upon the tectonic interpretation of typical seismic sections of the West Depression Belt in the East China Sea Shelf Basin, this paper systematically summarized the framework and structural styles of the West Depression Belt in different sags. Balanced cross-section technique and the extensional and compressional rates calculation are adopted for reconstruction of tectonic evolution histories in different tectonic evolutionary stages. The results show that the West Depression Belt experienced the Oujiang movement by the end of Paleocene and the Huagang movement by the end of Oligocene. Accordingly, the West Depression Belt was under obvious compression right after the deposition of the Paleocene Mingyuefeng Formation(E₁m) and Eocene Wenzhou Formation(E₂w) respectively upon the unconformity interfaces of T80 and T20. By quantifying the regional stress field, the paper also discussed the tectonic evolution of the West Depression Belt. The temporal and spatial variations in extensional and compressional rates of the depression belt represent local responses to the regional stress field, such as the change in convergence rate and motion azimuth in Mesozoic and Cenozoic among the Pacific plate, the Eurasian plate and the Indian plate.