ANACHRONISTIC FACIES AND ITS ORIGIN OF THE LOWER TRIASSIC IN THE LOWER YANGTZE-SOUTH YELLOW SEA AREA

As a special type of sediments in geological history, anachronistic facies developed widely of the Lower Triassic in the Yangtze region as a high quality carbonate reservoir. Based on the data from drilling cores and field sections, combined with previous studies, this paper analyzes and summarizes the characteristics and distribution pattern of the anachronistic facies in the lower Yangtze-South Yellow Sea region, and discussion its genesis. The results show that the anachronistic facies including thin-bedded limestone and zebra limestone, microbialite, wormlike limestone and flat pebble conglomerates, appeared right after the biological mass extinction by the end of Permian and disappeared immediately with the restoration of Mesozoic palaeoceanic ecosystem. The development of anachronistic facies is closely related to the paleostructure, palaeo-marine environment, palaeontological environment and sea level change, so the study of anachronistic facies is of great significance for further understanding of the palaeo-environment and oil and gas reservoirs of Early Triassic in the lower Yangtze-South Yellow Sea region.