Z2dn of Sichuan basin belongs to the last set of Neoproterozoic strata,and it is also the first sedimentary cover for Sichuan. The main lithology is the pure dolomite in light color,which underwent a complicated diagenesis,so its depositional environment is a topic of much controversy. Based on the field section in the periphery of the basin, drilling core, well logging data and analysis of analytical data,guided by petrology, sedimentology and petroleum geology theory, and combined with the modern stromatolites sedimentary characteristics, the authors analyzed characteristics of petrology, sedimentary environment of Dengying Formation. Some conclusions have been reached:①The rocks of Dengying Formation can be divided into 3 types and 12 subtypes. Poor algal section is mainly composed of dolomicrite,clotted dolomite and grained dolostone,mostly occurring at the early-middle stage of a complete sedimentary cycle. Rich alga section is mainly composed of straticulate dolostone,laminated dolomite and foam dolomite,mostly occurring at the middle-late stage of a complete sedimentary cycle.②The sedimentary facies of Z2dn of Sichuan basin is mainly shallow-water restricted platform facies,and it can be subdivided into 4 subfacies,i.e., algal mound, grain beach, flat and lagoon. The sedimentary facies of the study area is mainly algal mound,and the algal mound may be further subdivided into base, core, cap 3 microfacies.③Comprehensive analysis shows that the high quality reservoirs is obviously controlled by facies. In platform,the reservoirs of grained beach and algal mound, especially the composite body of"mound and beach complex",are of the best physical property,and gas exploration of Z2dn should be carried out around the microbolite in Sichuan basin.%提四川盆地震旦系灯影组属于新元古界最后一套地层，也是四川盆地第一套沉积岩盖层。岩性以质纯色浅的白云岩为主，并且经历了多期复杂的成岩作用，因此其沉积环境始终是研究的难点和争议的焦点。本文以盆地周缘的野外剖面、钻井岩心、测井资料及分析化验等资料为基础，以岩石学、沉积学和石油地质学等理论为指导，并结合现代叠层石沉积特征，对灯影组岩石学特征、沉积环境进行了综合分析。研究表明：①灯影组的岩石类型可分为3个亚类和12个微类，其中贫藻段主要由晶粒云岩、凝块状云岩、粒屑云岩等组成，通常发育于一个完整沉积旋回的早—中期；富藻段主要由层纹状云岩、叠层状云岩、泡沫状云岩组成，通常形成于一个沉积旋回中—晚期；②四川盆地灯影组沉积相主要为浅水局限台地相，可细分为藻丘、颗粒滩、台坪、潟湖4个亚相。研究区以藻丘亚相为主，藻丘可进一步细分为丘基、丘核、丘盖3个微相；③优质储层受相控特征明显，台内颗粒滩相和藻丘相储集物性最好，尤其是两者叠合形成的“丘滩复合体”。总之，四川盆地震旦系灯影组的天然气勘探将围绕着微生物岩展开。
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