Study On The Developmental Characteristics And Evolution Of The Ordovician Sedimentary Facies In The Western Tarim Basin

In this paper,the study area is mainly in the area of western North Tarim Basin.The study area contains:Yingmai2 area,Halahatang area,Hadexun area.The formation of Ordovician was devided into:Penglaiba Formation,Yingshan Formation,Yijianfang Formation,Tumuxiuke Formation,Lianglitage Formation,Sangtamu Formation in the Western of Northern Tarim Basin.By the observation of the rock core,core slices,I defined the rock type with the help of sedimentary petrology.It is very comprehensive.Penglaiba Formation is represented by sparry grain limestone,micrite,and dolomite bearing limestone.There are no well which drilled at Penglaiba Formation in the southern of studying area.But it can be conjectured that its lithology are dolomite and dolomite bearing limestone by the data of Lunnan and Ha6 well.Yingshan Formation comprises mainly micrite,clips thin calcarenite.And the lower of the formation contains more dolomite.Yijianfang Formation is made of grainstone,and a little of micrite,Biolithite can also be found in this area.he lithology of Tumuxiuke Formation have more mud than other's.Micrite is dominated,with small amount of mudstone and bioclastic limestone.Lianglitage Formatiaon characterized by micrite.Most of them are nodular limestone.Grained limestone can be found in Liang-1 section and Liang-3 section.Sangtamu Formation deposities terrigenous clastic and limestone.By the sedimentary theory,The Sedimentary Facies of Ordovician in the Western of Northern Tarim Basin is subdivided into 3 phase region:carbonatite plateau region,slope region,basin region.and it a divided into 7 facies and many microfacies.Restricted platform facies is recorded in Penglaiba Formation,Because of higher terrain,The Northern of studying area are open platform facies.Semi-confined platform facies and open platform facies in Yingshan Formation.Submerged platform facies and slop facies in the Tumuxiuke Formation.Platform edge faciesin the Lianglitage Formation.For the rise of sea level,the facies turned into mixture shelf in Sangtamu Formation.In this study,I found the sedimentary models in different periods in the types of sedimentary facies and evolution characteristics:Yingsha Formation and Yijianfang Formation represent carbonate platform sedimentary model.Submerged platform-slop sedimentary model are represent by Tumuxiuke Formation.Platform margin-slop sedimentary model leads a central part in Lianglitage Formation.