塔里木盆地苏盖特布拉克地区下寒武统肖尔布拉克组碳酸盐岩微生物建造特征*

塔里木盆地苏盖特布拉克地区下寒武统肖尔布拉克组发育3种类型碳酸盐岩微生物（蓝细菌）建造，即下部微生物丘状和层状建造、中上部微生物礁和顶部叠层石建造。微生物丘状和层状建造的特点是似层状孔洞和纹层结构发育，形成于潮下高能带，与微生物席粘结有关，分布相对稳定。微生物礁是由枝状或丛状微生物骨架生长和微生物席粘结两种方式形成，分布较广，可分为两大期：第1大期发育在海退背景下，呈宏观块状建造特征；第2大期则发育在较大的海侵背景下，呈现两期点礁特征。叠层石建造发育在更大范围的海侵背景下，超覆于点状建造之上，要求的水动力条件相对较强，由微生物粘结作用形成，其中叠层石和核形石是其重要标志，仅分布在研究区北部的苏Ⅱ、苏Ⅲ和苏Ⅳ剖面近顶部。

Carbonate rock microbial construction of the Lower Cambrian Xiaoerblak Formation in Sugaitblak area, Tarim Basin

There are three kinds of carbonate rock microbial(cyanobacteria)constructions in the Lower Cambrian Xiaoerblak Formation in Sugaitblak area,Tarim Basin,including microbial mounds and laminated constructions at the lower part,microbial reefs in the middle and upper part and stromatolite constructions at the top.The microbial mounds or laminated constructions are characterized by the stromatactoid cavities and laminated texture formed in the subtidal high energy zone.The constructions with a wide and stable occurrence were related with sticky microbial mats.The microbial dendritic or shrub structure and its cohesive action are developed in reefs,formed by microbial growth and sticky microbial mats.They are widely spread in the study area.There are two stages of microbial reefs.At the first stage macroscopic massive buildups are developed during the regression setting,while at the second stage,two stages of point reefs are developed during the transgression setting.The stromatolite constructions are formed during a more broad transgression setting,overlapped on the point microbial reefs,when the hydrodynamic force was stronger.This type of microbial buildups is formed by microbial bonding and characterized by stromatolite and oncolite.They are only developed at the top of Su Ⅱ,Su Ⅲ and Su IV sections.