Abstract: Chang 6-Chang 7 members of Yanchang formation in Longdong area in Ordos basin are divided into a large scale base-level cycle and five medium scale base-level cycles by well-seismic integrated method. It is shown that in view of time the turbidites of the members are distributed in the middle-late period of the decline hemicycle and early period of rising hemicycle of medium scale baselevel cycles, and in view of space they are distributed in the basin slopes in front of braided river delta and the lowland of ancient topography in the basin plain with the distribution range migrating to the central basin gradually as the large scale base-level declines. The distributions of turbidites in the study area are controlled by four factors: The tectonic settings of the basin and peripheral areas control turbidite development from the macro level; the regional tectonic activities provide trigger mechanisms for turbidite development; the changes of base level cycle control the formation and distribution of turbidite; the ancient topography of prograding delta area determines the flow direction of turbidity currents in delta front and the depositional position. The turbidite deposit in Longdong area is of prime conditions for petroleum accumulation, being as an significant succeeding domain for incremental reserves and production in Changqing oil field in the future.

Key words: Ordos basin, Longdong area, Yanchang formation, turbidite, high resolution, sequence stratigraphy, distribution rule