SIGNIFICANCE OF SLOPE BREAK ZONE IN EVOLUTION OF KARST RESERVOIR IN ORDOS BASIN

Weathering crust on the top Ordovician in the Ordos Basin kept stable relief during the evolution from the Benxi stage to the early Middle Triassic and was high in the central part but low in the eastern part. A steep slope zone is recognized between the central uplift and the eastern depression and can be classified as a slope break zone resulted from the double action of tectonism and erosion. Therefore, the karst evolution process of the basin is integrated with the slope break zone theories to analyze the relations between the development of karst reservoirs and the background of slope break zone during the shallow burial to deep burial stages. It is proposed that the slope break zone is the most favorable area for the development of karst reservoirs.