塔中16井区晚奥陶世良里塔格组的沉积相

塔里木板块中央隆起区的塔中低隆带上奥陶统凯迪阶良里塔格组礁相群落是晚奥陶世生物礁演化阶段的例证。该组分为5个岩性段。塔中16井区位于塔中Ⅰ号断裂坡折带向台地内部延伸的缓坡区,海水深度和水流能量显著控制碳酸盐岩的岩相分布。良里塔格组所赋存的典型动物格架礁集中于台地边缘的高能区,而塔中16井区不属于大型动物格架礁建造的富集区域,其早期多以低能带沉积为主,特别是塔中16井和塔中166井灰泥坪常见;晚期常见高能滩相和灰泥丘以及近礁沉积,可划归为台缘坡折带大型格架礁建造向台内的延伸区,这里的水深和能量变化更频繁。偏西北的井在良二段沉积之后抬升较早,东南的塔中161井则保存部分良一段沉积。

SEDIMENTARY FACIES OF THE LATE ORDOVICIAN LIANGLITAG FORMATION IN THE WELL BLOCK TAZHONG 16,CENTRAL TARIM,NW CHINA

Reef complexes of the Lianglitag Formation(Katian,Upper Ordovician)in the Well Block Tazhong 16,Central Tarim High,Tarim Block,NW China are representatives of the evolutionary units of Ordovician reefs.The Lianglitag Formation is composed of five lithological members.The Well Block Tazhong 16is assigned to the ramp belt of the Tazhong Slopebreak I,where the water depth and current energy played significant role for the sedimentary pattern of the carbonate lithofacies.Typical metazoanal reefs are concentrated along the high-energy belt of the platform margin.In contrast,the Well Block Tazhong 16isn't characterized by the reef thriving realm.Lower energy sediments especially lime flats are commonly occurred from the lower members of the formation in the wells of Tazhong 16and 166.Facies of the high-energy bank,carbonate mudmounds as well as reef-surrounding sediments are richly yielded from the upper members.Therefore,it could be considered as the extension area of the large metazoanl reefs from the platform margin toward interior platform.Water depth and current energy are diverse herein.The wells in the northwest part were uplifted earlier since the forming of the Member 2,however,Well Tazhong 161at the southeastward maintained a submarine environment and resulted in the uppermost unit of the Member 1.