Abstract:

The calcisponge reefs of the Upper Permian Changxing carbonate platform in Eastern Sichuan and Western Hubei Provinces can be divided into three types: rimming frame-work reefs developed on the eastern margin of the platform, linear or point framework reefs located within the platform and baffling point reefs on the ramp of the western plat-form, the framework reef complexes of which, both rimming and linear or point, are favourable oil and gas reservoirs. The formation and distribution of reef bodies are mainly controlled by faulting, especially synsedimentary faulting. The reef bodies developed throughout the whole Changxing stage, the best of which are middle and late stages. From the end of Changxing to Early Triassic, a rapid rising of sea-level took place, resulted in drowning out of the entire platform and all the reef bodies.