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.