THE LAW OF SEDIMENTARY FACIES DEVELOPMENT OF ORDOVICIAN CARBONATE ROCKS IN THE LUNNAN'S PERIPHERY,TARIM BASIN

The Ordovician strata are well developed in the Lunnan's periphery of Tarim Basin,and are mainly composed of marine carbonate rocks and terrigenous clastic rocks.The analysis of sedimentary facies indicates that Yingshan Formation,Lower-Middle Ordovician,is the deposits of bank and interbank sea sub-facies in a territorial open platform facies.The shoal and patch reef sub-facies in territorial seawater shallowing open platform facies were developed in Yijianfang Formation Middle Ordovician.The submerged platform-slope facies were developed in Tumuxiuke Formation,Upper Ordovician.Lianglitage Formation,Upper Ordovician,is the deposits of carbonate platform edge-slope facies under the background of the Late Ordovician transgression.Two stage reef and shoal bodies are developed in the region,the first grew in the Yijianfang Formation,Middle Ordovician,the second at the top of Lianglitage Formation,Upper Ordovician.These reef and shoal bodies have distinct sedimentary environment and distributions.The Ordovician carbonate sedimentary facies are wholly distributed in the form of close north-south each other.Every facies on the close east-west direction has order to scatter,and obviously lateral migrate with time.