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. The 2nd 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.