Abstract: the analysis of depositional framework and evolution of Bachu Formation in Tarim Basin, the authors of the paper attempt to provide a new idea for a favorable sandbody and the prediction on assemblage of reservoir and cap beds. According to the principle of ubiquity of diachronism, it is recognized that the Donghe Sandstone Member and Low Mudstone Member of Bachu Formation are a diachronism lithostratigraphic unit of the total basin range and that bioclastic limestone can be considered as a precise time lithologic criteria. Taking the analysis of sedimentary tectonic background as the foundation, it is indicated that there are two Prototype basins in Tarim Basin, including cratonic margin depression and intracratonic depression. The depositional framework and development of Bachu Formation in Tarim Basin have been controlled by the ancient landform elevation caused by tectonic movement with high in the east and low in west, and progressive sea transgression from west to east. Combining with fine interpretation of sedimentary facies, Bachu Formation may be divided into four depositional evolution stages: initial sea transgression in primary stage, clastic shore and shelf development in early days, clastic shallow shelf development in medium time, carbonate platform deposition in an advanced stage.

Key words: depositional framework, depositional evolution, sedimentary tectonics, Bachu Formation, Tarim Basin