CRETACEOUS TRANSGRESSION IN THE SOUTHERN EAST CHINA SEA SHELF BASIN AND ADJACENT LAND AREAS: EVIDENCE AND GEOLOGICAL SIGNIFICANCE

There seems a thick and wide Mesozoic in the southern part of the East China Sea Shelf Basin under the Cenozoic, in which a large reserve of gas and oil has been discovered. However, the Mesozoic palaeogeographic pattern of the area remains unclear, that restrict the further exploration of the basin. In this paper, we made an integrated analysis of lithofacies and palaeogeography for the Cretaceous with a few drilling data and incomplete outcrops upon the basis of single factor facies analysis. It is revealed that the distribution of depositional characteristics, such as the paleontological, mineralogical and geochemical indicators, is all in a transgressive pattern from Radiolarian (Huatung basin)-Ammonite and Lamellibranchia (Taiwan)-Glauconite (the East China Sea Shelf Basin)-Shipu Limestone (Xiangshan, Zhejiang)-Marine fish (Zhejiang)-Phaeophyta, Rhodophyta and Plants (Wuyishan, Fujian) from SE to NW. The depositional environment changes in a general trend from abysmal environment to shallow sea, transitional zone, and to land. This trend probably indicates that the direction of transgression in the early Cretaceous was from SE to NW, which controlled the lithofacies and palaeogeographic pattern of the early Cretaceous in the southern part of the East China Sea Shelf Basin and adjacent land areas. High quality source rocks, such as those in the Chawan Formation, were formed in the transgression.