贵州习水中二叠统栖霞组有孔虫形态群及沉积微相特征OA

In recent years,the Middle Permian Qixia Formation in the Sichuan Basin has attracted considerable attention for oil and gas exploration,but its sedimentary model remains highly controversial.In this study,48 species in 22 genera(including subspecies and indeterminate species)of foraminifera were identified in the well-outcropped Wenshui section in Xishui,Guizhou Province,and divided into six morphogroups(M1-M6).Based on the study of thin-section rock structure,12 types of microfacies were recognized:coralline algae wackstone,burrow mudstone,bioclastic wackstone,densely packed bioclastic packstone,foraminifera packstone,foraminifera coralline algae packstone,dasycladale bioclastic packstone,fecal pellet wackstone,non-fossil mudstone,peloid grainstone,foraminifera dasycladale grainstone,and foraminifera Ungdarella grainstone.The Qixia Formation in Xishui,Guizhou Province is mainly a carbonate platform without rims,in which a continental shelf,slope,and open platform facies developed.The open platform facies can be divided into shallow open platform subfacies,deep open platform subfacies,and platform shoals subfacies.The platform shoals subfacies contain abundant M3c,M4,M5,and M6 morphogroup foraminifera,shallow open platform subfacies,and deep open platform subfacies containing abundant M3a and M3b morphogroup foraminifera;however,the deep open platform subfacies lack Dasycladales.