As a whole

the Upper Permian Changxing Formation-Lower Triassic Feixianguan Formation in northeastern Sichuan basin were deposited as carbonate platform.The extensive platform was cut into platform-highs and platform basins by fossil fractures.Being controlled by Kaijiang-Liangping platform-basin

relatively symmetrical carbonate sedimentary systems

similar to Wilson's facies pattern

were developed on both sides of the basin in late Changxing to early Feixianguan age

but shelf facies were poorly developed.It is possibly due to the shallow depth

narrow width and rapid facies change of the platform-basin.A second-order eustatic sea level change during this period resulted in the widely development of transgressive bioherm in Changxing Formation and regressive oolitic shoals in Feixianguan Formation

both of which would be the most favorable reservoir facies belts.The bioherm and oolitic shoal facies belts continuously migrated laterally and upraised vertically.They were mainly developed on both sides of the platform-basins and characterized by discontinuous zonary distribution

which were obviously controlled by sedimentary facies belts.