Sedimentary Characteristics and Coal-accumulation Pattern of the Xishanyao Formation in Southern Margin Area of Junggar Basin

Based on the analyses of data about drills,loggings,outcrops and palaeophytes,this paper studied the sequence stratigraphy of the Xishanyao Formation in southern margin area of Junggar basin.Two sequences of SQ1 and SQ2 were identified with the classic sequence stratigraphy method,and six system tracts were subdivided according to the superposition style of strata and sedimentation cycle.The characteristics of sedimentary evolution of the Xishanyao Formation were also defined by analyzing the sedimentary environment.In sequence SQ1,a river-dominated delta was developed;a stable peat swamp was formed in the lake edge and flood plain area,and stable and thick coal seams were also formed after a long-time and wide-range intense coal accumulation.In sequence SQ2,owing to the tectonic transformation and the strong denudation,the coal accumulation was gradually weakened.The result provides the basis for further exploration of coal resources in the Xishanyao Formation in southern margin area of Junggar basin.