塔里木塔中油田上奥陶统良里塔格组滩相

塔里木板块塔中井区上奥陶统凯迪阶良里塔格组的沉积序列由碳酸盐岩台地区礁滩复合体灰岩构成,显示晚奥陶世由高生物多样性形成的暖水浅海域生态组合。根据滩相灰岩的颗粒组成,可次分为生屑为主、生屑-内碎屑混合、内碎屑为主的三大类型,其中灰泥充填和亮晶方解石胶结均有。部分滩相是礁相单元的近源沉积,而内碎屑和生屑经各种营力改造后多以不同比例混合独立形成滩相。滩中的颗粒粒径一般多小于厘米级,仅部分核形石、珊瑚等颗粒可达到砾级,这些滩多堆积于最大风暴浪基面之上的深度。

BANK FACIES FROM THE UPPER ORDOVICIAN LIANGLITAG FORMATION IN THE CENTRAL TARIM OIL FIELD,NW CHINA

The limestones of the Katian Lianglitag Formation(Upper Ordovician)in the well blocks of Central Tarim Platform,NW China are composed of reef-bank complexes.The paleoecological associations are diverse in biotic structures and thus considered as indicators of a warm and shallow marine setting.The bank faicies are subdivided into the bioclastic,bioclastic-intraclastic mixed and intraclastic types according to the dominated compositions.Micritic filling and spar cementation are both recognized.Some bank units are assigned to the subfacies of the reefs.However,intraclastics and bioclastics reformed in different conditions and mixed in varying proportions are more likely of the key roles for the formation of banks.Grain-sizes are mostly less than centimeters in diameters except some oncolitic grains and corals.These banks were likely formed above the maximum wave-base.