CHARACTERISTICS OF STRATIGRAPHIC DISTRIBUTION IN THE MIDDLE UPLIFT OF SOUTH YELLOW SEA

The middle uplift of South Yellow Sea is tectonically one of the most stable areas in the basin, and it has received great concerns since its lower Paleozoic is a potential hydrocarbon-bearing prospect area. Wavelet analysis method has been used to deal with gravity and magnetic anomalies in the South Yellow Sea to obtain the crystalline basement shape of the middle uplift, and combined with regional geology and seismic section data, some new understandings on stratigraphic distribution features in the middle uplift are as follows:(1)The crystalline basement of middle uplift is not a flat "plain", and its geographic fluctuation pattern could be summarized as "three uplifts and two depressions"; (2)Because of the Indo-China movement, the main strata in middle uplift were Sinian-lower Permian series, while both Qinglong-limestone of lower Triassic and Longtan-coal seam of upper Paleozoic have been completely eroded; (3)The depocenter of the lower Paleozoic was located at the depressions of the crystalline basement,and it was distributed non-continuously due to the volcanic activities and magma intrusion;(4)There are volcanic rocks scattering in the middle uplift showing the tendency of "more in the east, less in the west".