Abstract: Between the Middle -Upper Ordovician and Lower Ordovician in Tazhong low arch area assumes the contact relationship of an angular unconformity for lack of Dawan and Guniutan orders in Lower Ordovician as well as Miaopo order in Middle Ordovician. In its suroundings, Manjiaer sag, Tadong low arch and Tangutsbas sag are successive and transitional sedimentations. The stratigraphic correlation and depositional facies analysis showed that isolated carbonate tableland was developed in Middle-Late Ordovician in Tazhong area, with some subfacies of developed grain bank,lime mud hill and skeletal reef in platform suroundings. The depositional evolution of Middle-Late Ordovician underwent three periods, i.e. the rising outcrop period in late period of Early Ordovician to middle period of Middle Ordovician, the isolated carbonate platform-developed period in Middle-Late Ordovician to middle period of Middle Ordovician and the peperite platform-developed period of composite carbonate rock and clastic rock in Linxiang Wufeng stage of Late Ordovician.

Key words: Tarim basin, Middle, Middle Ordovician, Late Ordovician, Sedimentary characteristics, Evolution