Sedimentary Facies and Evolution of the Permian and Triassic Strata in the North of Sichuan Basin

The sedimentary facies of the permian and triassic strata in the north of Sichuan Basin is detailedly studied on the basis ofsedimentary facies of single wells, seismic data as well as surface outcrop data. Two depositional systems are recognized, and they arecarbonate platform and carbonate ramp. On the basis of depositional facies analysis and comprehensive consideration ofpaleogeography, sedimentary environment, the sedimentary evolution of permian and triassic stratan is cleared. The process is fromcarbonate ramp to carbonate platform. The sedimentary system of lower Permian Qixia formation, Maokou formation and upper PermianWujiaping formation are carbonate ramp, and the sedimentary system of changing formation is rimmed carbonate platform. Till the lateEarly Traissic Epoch, the north of the Sichuan basin evolved to uniform carbonate platform. The result may be a reference to theexploration of Sichuan Basin.