新疆塔里木塔中井区上奥陶统良里塔格组的生物绑结岩

塔里木板块塔中井区上奥陶统凯迪阶良里塔格组灰岩中底栖固着型的钙质微生物、钙藻以及动物苔藓虫、珊瑚、层孔虫,可通过障积、盖覆和粘结等方式形成多种类型的生物绑结岩。对15口井部分岩芯以常用的绑结岩分类方案作岩石学微相分析,并描记底栖固着型生物颗粒的形成特征。菌藻类可在内碎屑表面以包结方式形成粘结岩;钙藻,特别是分枝状钙藻可形成障积岩;层孔虫可被隐藻层纹包结,也可单独形成小型盖覆岩;床板珊瑚格架岩可大量障积生屑和灰泥基质;苔藓虫在动物格架岩比例上占优,可与菌藻类粘结岩互相包结生长,也可独立形成局部小型障积岩。对比巴楚露头区同期藻丘中的绑结岩特征,显示塔中良里塔格组代表晚奥陶世由高生物多样性形成的礁滩复合体生态群落。

BOUNDSTONES FROM THE UPPER ORDOVICIAN LIANGLITAG FORMATION IN THE CENTRAL TARIM,XINJIANG,NW CHINA

High diversity benthic biota,especially some sessile groups play an important roles in the formation of the boundstones of the reef complexes from the Upper Ordovician Lianglitag Formation in the Central High,Tarim Block,Xinjiang,NW China.The calcimicrobes,calcareous algae,stromatoporoids,corals as well as bryozoans are potential constructors of the bafflestones,bindstones and coverstones.Current limestone classification schemes for the analysis adopted of the lithological features.Microfacies data from the 15 drilling cores illustrate their differentiations in palaeoecological indexes.Crusts and bindstones are common microbial types.Calcareous algae,stromatoporoids,corals and bryozoans are mostly for the formation of the varieties of the bafflestones and coverstones.Compared to the coeval carbonate mudmound from the Bachu outcrops,which are of the monotonous microbial-dominated boundstones,the Tazhong High shows a more complexity by the diverse metazoanal compositions and lithological catalogues.Such a pattern implies that multiple evolutionary communities of the Late Ordovician reef are coevally occurred within the same carbonate epicontinental sea water.