Microfacies of Qixia Formation and Maokou Formation in Shizhu,Chongqing,China

The Middle Permian Qixia Formation and Maokou Formation sedimentary microfacies in Shizhu of Chongqing are the typical representatives in Sichuan Basin.Combined with the profile measurements in the field and the indoor microfacies analysis and according to the normal microfacies of Wilson,ten types of microfacies are recognized,that is green algal grainstone,marlite,fusulinid wackestone,bioclastic packstone,reef micrites,bioclastic-intraclastic packstone,dolomitizationsilicification mud microcrystalline limestone,algal-mat(patellate)packstone,foraminifer packstone and bioclastic packstone.Combined with the analyses of the evolution sequences of lithological microfacies groups and the sedimentary facies,Qixia Formation and Maokou Formation are divided into the carbonate rock gentle slope and the carbonate rock platform.The carbonate rock gentle slope is again divided into the inner gentle slope and the outer gentle slope.The carbonate rock platform is again divided into the open platform,platform margin,foreplatform slope and some sedimentary microfacies.The sedimentary facies model is built and its evolution characteristics are discussed in this paper.The study provides important data for the regional geological research and the oil and gas exploration and development.