IDENTIFICATION OF THE DETACHMENTS IN THE FORELAND FOLD-THRUST BELT IN SOUTHERN MARGIN OF JUNGGAR BASIN

The foreland fold-thrust belt in the southern margin of Junggar Basin is located in the north side of the Tianshan orogenic belt,experienced superimposition and juxtaposition of multi-prototype basins from the Carboniferous and formed a series of possible detachments,which are the main factors controlling formation and evolution of skin-typed structural styles and causing the unconformities between the upper and the lower structures.Based on comprehensive analysis of the outcrops and interpretation of seismic data in this area,six detachments are identified,which are the Middle Permian Lucaogou and Hongyanchi Formations,the Lower Jurassic Badaowan Formation,the Middle Jurassic Xishanyao Formation,the Cretaceous Tugulu Group,the Palaeocene Anjihaihe Formation and the Neocene Taxihe Formation from the deep to the shallow.There exists one or more detachments in different segments of the foreland fold-thrust belt whose eras have the tendency of becoming new from east to west.The identification of the detachments are significant to the structure modeling and trap determination.