Influence of Thrust Tectonism on Sequence Contexture of Southern Junggar Foreland Basin and Its Significance

Abstract:

The southern margin of Junggar Basin was the foreland basin at the tectonic underground of intense thrust of North Tianshan in the Neocene.The Shawan FormationTaxihe Formation of Neocene was divided into one secondorder sequence,two thirdorder sequences,which were separated by angle unconformity,parallel unconformity,and transformation surface of depositional environment.All the depositional contexture of the secondorder sequence reflected the evolutionary process which was from flexural subsidence caused by foreland thrust to rebounded uplift,the depositional contexture of Sequence 1 was obviously controlled by thrust tectonic activities,and rebounded uplift influenced the inner depositional contexture of Sequence 2 which was in the period of tectonic relative quiet.The inner evolution of thrust tectonic activities of Neocene restricted the synchronous depositional systems of alluvial fanfan delta.Influenced by the thrust tectonic activities,the fan delta sand body of Sequence 1 (Shawan Formation) advanced continuously towards the basin,its lateral communicated,its vertical mutually superimposed to form considerable thick reservoir body,which was on the earlier deep lake oil source rock,and near to the oil source center,the overlying massive fine sediments of Sequence 2 (Taxihe Formation) may be favorable cap formation,large oil and gas field could easily be formed.