AN APPROACH TO MICROFACIES ANALYSIS FOR CARBONATE ROCK IN LIANGLITAGE FORMATION OF THE UPPER ORDOVICIAN, SOUTHERN MARGIN OF KETAKE UPLIFT, TARIM BASIN

It is a basic geologic issue whether the Lianglitage Formation of the Upper Ordovician,southern margin of Ketake Uplift,Tarim Basin,is or not consists of sedimentary assemblage of reef-shoal,just likely to counterparts that occurs in northern margin of Ketake Uplift.Based on the microfacies analysis of carbonate rocks in the cored intervals of Lianglitage Formation in Well Zhong-2,six microfacies records of bioclastic-bearing algal pellet micritic,bryozoans and coralline framestone,bindstone,bafflestone have been recognized,as well as of six major stacking patterns of reef-shoal,reef-shoal-mound,coarse pellet shoal,beach-algal mats,algal or bioherm mound-algal mats,algal mats-subtidal low energy.From lower to upper cored intervals of Lianglitage Formation,the vertical facies distribution are respectively indicative of a gradual deepening trend,a sea-leval fluctuation and two shallowing upward succession carbonate cycles,and account for a serial of stacking pattern of pellet shoal,algal or bioherm mound and reef framestone in the first three cored intervals,with the prominent of highstand progressive system tracts of reef-beach and retrograde terrace reef-shoal developed during sea-level rising period.