Sequence stratigraphy and depositional systems in the fourth member of the Shahejie Formation in the Damintun depression

The Palaeogene strata in the Damintun depression may be divided into one second-order sequence and two third-order sequences on the basis of lithologic,well logs,outcrops and seismic data.In the fourth member of the Shahejie Formation in the Damintun depression,the depositional systems include the fan-delta to lake depositional system and the nearshore turbidite fan to lake depositional system,and the sedimentary facies types consist of the fan-delta facies,lake facies,and locally nearshore turbidite fan facies.The favourable areas for hydrocarbon accumulation are delineated by means of seismic inversion based on the research of depositional systems.