Abstract:

Observation and analysis of numerous outcrops and cores as well as laboratory tests of samples from the Qixia Formation in western Sichuan Basin reveal that the formation mainly consists of bioclastic limestone，calcarenite， micrite，and leopard limestone. There are mainly three fossil assemblages，including brachiopodsˉalˉgaeforaminifera，corals and thin shell brachiopods. They were formed in platform，slope and slopeˉbasin environments respectively. Judging from geotectonic settings，bank features of platform edge and slopeˉbasin facies，and the relationship between slope facies and platform edge facies etc，we conclude that the Qixia Formation in western Sichuan Basin is the carbonateˉfringed platform depositional system with slope，platform edge bank and open platform as the main facies，of which the platform edge bank facies is widely distributed and the most favorable for hydrocarbon accumulations.

Key words: platform edge bank facies, fringed platform, depositional system, Qixia Formation, Middle Perm ian, western Sichuan Basin