川北小南海剖面栖霞组岩石微相及沉积环境

近年来，四川盆地西北部下二叠统栖霞组已成为油气勘探的热点和重点。但川北地区勘探程度较低，钻井和剖面资料较少，栖霞组岩石类型分类粗略，沉积模式尚存争议。故选取川北地区露头出露良好的小南海剖面，通过实测观察和室内岩石薄片鉴定，共识别出4类11种岩石类型，并在此基础上分析其岩石微相类型及沉积环境。结果表明:川北地区栖霞组为开阔台地相沉积，生物化石类型丰富，碳酸盐颗粒强烈泥晶化，发育相对低能的似球粒颗粒滩，有别于鲕粒滩和生物碎屑滩，为川北地区下二叠统栖霞组台地沉积模式提供了新的依据。似球粒浅滩的形成环境对进一步认识上扬子二叠纪古地理环境具有重要意义，可为川北地区在今后的勘探工作提供理论指导。此外，梁山组—栖霞组应为一个完整的三级层序，海平面变化是栖霞组沉积相横向迁移和纵向演化的主要控制因素。

Carbonate Microfacies and Sedimentary Environment of Qixia Formation in Xiaonanhai Section,Northern Sichuan

In recent years， the Early Permian Qixia Formation in the northwestern Sichuan Basin has attracted considerable attention for oil and gas exploration. However， the classification of rock types of Qixia Formation is only roughly divided， and the sedimentary model is controversial due to the scarcity of exploration and drilling data in northern Sichuan. In this study， the well?outcropped Xiaonanhai section was selected for field observation and thin?section identification. Eleven rock types in four categories were defined. In addition， the rock microfacies types were analyzed and sedimentary environment was discussed. The results show that carbonate grains are strongly micritized into peloids， indicating that they were deposited in relatively low?energy peloid shoals with abundant fossil species， differing from oolitic and bioclastic shoals. Thus， the Qixia Formation in northern Sichuan is interpreted to be an open?platform facies. Moreover， the Liangshan and Qixia Formations form a complete third?order sequence. The study provides new data for deciphering the platform sedimentary model； the peloid shoal sedimentary environment has great significance for further understanding the paleogeography of the Upper Yangtze region during the Permian， and for guiding further oil and gas exploration in the northern Sichuan area. Sea level eustacy exercised the main control over horizontal migration and vertical evolution of the sedimentary facies in the Qixia Formation.