Sequence Stratigraphy of the Middle and Lower Triassic in Southern Sichuan Basin

There are Leikoupo Formation,Jialing Formation,Tongjiezi Formation and Feixianguan Formation of the Middle and Lower Triassic in Southern Sichuan basin.The Middle and Lower Triassic gas field,southern Sichuan may be divided,on the basis of thin sections,well logs and seismic data,into five third—order sequence.It mainly includes partial exposure sequence unconformities interface and lithology and lithofacies conversion interface.