Sequence Stratigraphy Characteristics and Main Controlling Factors of the Tectonic Active Basin：As an example from Permian of the Kebai Area in the northwestern Junggar Basin

Key words: 
• Junggar Basin

Abstract: The Kebai fault zone in the northwestern Junggar Basin is a largescale imbricate thrust system which originated in Permian. The tectonic activity played an important role in controlling the sedimentary process. Permian is a mixing accumulated formation which contains volcanics and clastic rocks. Through the analysis, it has been pointed that Permian is a laminar formation and has unconformities that are formed by the relative lake level change and can be regarded as the sequence boundary. Permian is divided into 5 secondorder sequences and 12 thirdorder sequences according the unconformities and the stratal surfaces. Lower Permian (PSQ1PSQ7) is characteristic as volcanic facies and sedimentary facies coexisting; the main sedimentary facies of MiddleUpper Permian are fluvial fan, fan delta and lacustrine facies. The main control actions of the tectonic activity to the sequence are tectonic subsidence, volcanic activity and features of palaeogeomorphic. The essence of the tectonic subsidence is flexural subsidence leaded by the thrusting orogenesis, which reflects the basinmountain coupling process between foreland thrusting action and the flexural subsidence. Flexural subsidence is the internal and dominating factor; the volcanic rock mass which is formed by the volcanic action and deposited fast had important impact on the formation and evolution of the sequence; the slope breaks that are formed by tectonic activity controlled sequence architecture and the sedimentary filling.