塔北奥陶系碳酸盐岩沉积演化特征及台地发育模式

通过对塔北奥陶系碳酸盐岩沉积相类型、相带区域组合及分布特征的研究,根据岩石特征、沉积结构和相序特征的分析,建立了塔北奥陶系碳酸盐岩的沉积演化模式。研究认为塔北下奥陶统蓬莱坝组、中下奥陶统鹰山组、中奥陶统一间房组和上奥陶统吐木休克组沉积相横向分布较稳定。蓬莱坝组、鹰山组鹰四段、鹰三段为局限台地相;鹰二段为半局限台地相;鹰一段和一间房组属于开阔台地相,但向上水体不断变浅,一间房组沉积时期开始出现点礁;上奥陶统吐木休克组沉积时期区域整体沉降,为沉没台地-斜坡-盆地沉积。上奥陶统良里塔格组沉积时期盆地整体抬升,区域沉积厚度和沉积相出现较大变化,早中期发育碳酸盐开阔台地相,后期为典型的台地边缘相。

Sedimentary evolution and platform development models for the Ordovician carbonate rocks in northern Tarim Basin

The sedimentary models for the Ordovician carbonate rocks in northern Tarim Basin are constructed on the basis of sedimentary facies types,associations and distribution in integration with cores,sedimentary structures and sedimentary facies sequence analysis.The distribution of the sedimentary facies is laterally extensive in the Lower Ordovician Penglaiba Formation,Middle-Lower Ordovician Yingshan Formation,Middle Ordovician Yijianfang Formation and Upper Ordovician Tumuxiuke Formation in northern Tarim Basin.The Penglaiba Formation and 4th and 3rd members of the Yingshan Formation are ascribed to the restricted platform facies.The2nd member of the Yingshan Formation is assigned to the semi-restricted platform facies.The 1st member of the Yingshan Formation and Yijianfang Formation belong to the open platform facies with shallowing-upward water depths.The patch reefs were initiated during the deposition of the Yijianfang Formation.The Tarim Basin was wholly subsided during the deposition of the Upper Ordovician Tumuxiuke Formation,constituting the drowned platform-slope-basin deposits.Afterwards,the Basin was wholly uplifted during the deposition of the Upper Ordovician Lianglitage Formation,where the open carbonate platform facies occurred during the early and middle stages,and then the typical platform-margin facies appeared during the later stages of the deposition.