Research On Pre-Tertiary Seismic Stratigraphy And Structural Characteristics Of The South Yellow Sea

The South Yellow Sea Basin, located in the continental shelf between China and Korea, is one of our country's offshore petroliferousbasins. Considering the tectonic position, the South Yellow Sea Basin is the subject of Lower Yangtze block. It is actually a superimposed basin formed by the polyphasic deposition of marine middle-Paleozoic and continental Meso-Cenozoic on a pre-Sinian metamorphic basement.Due to the limited level of the survey, exploration and study of the South Yellow Sea, also the lacking of the effective data of the target layer, the ambiguous feature of its geologic structure and the unclear history of its geologic evolution, its oil and gas potencial is diffcult to forecast. Ranking it as one of the first study targets of our country's strategic petroleum target area selection and evaluation is the most effective and realistic way to develop new offshore oil and gas resources and study the basic geology and petroleum geology of the South Yellow Sea as well as its adjacent area. It is also one of the most effective ways to promote the oil-gas exploration of the pre-Tertiary oil-gas resources in North China. Research on the pre-Tertiary oil and gas perspect of the South Yellow Sea is significant for energy exploration in China. At the same time, because of the special geographic location of this district, with the implement of UNCLOS(United Nations convention on the Law of the Sea ) in our country, it also has very important realistic significance for us to protect the equity and the exploration of our sea, carry out a deep-going study of Seismic stratigraphic the South Yellow Sea and find out the issues like structure, style, factor, regularities of distribution of this district.According to the seismic section collected and processed in recent years, contrast to the north jiangsu basin, and combining with the development conditions and distribution regularities of the regional stratigraphic, we calibrated the seismic-geological strata, analysed the seismic stratigraphic attribute, builded the stratigraphic sequence framework and studyed the strata distribution and tectonic evolution characteristics of the South Yellow Sea Basin.Based on the structure and characteristics of seismic reflection profiles, eight kinds of characteristic wave—T₂,T₇,T₈,T₉,T₁₀,T₁₁,T₁₂ and Tg were comparatively interpreted in the South Yellow Sea Basin. Combined with regional stratigraphic and tectonic features, according to the classfication principles of seismic sequence, the South Yellow Sea Basin is divided into I, II, III, IV, V, VI, VII, VIII and IX nine seismic sequences from top to bottom.Through the comprehensive study of regional seismic section, from the two aspects of constructing and transforming, the South Yellow Sea's marine strata is preliminarily divided into five secondary structural units—Trinidad rock pushover belt, Yantai Thrust Belt, Laoshan Fault-Uprising Belt, Qingdao Fault-depressed Belt and Wunansha Uping-Fold Belt from north to south. The South Yellow Sea's marine strata develops five groups of fault syetem—NNE, NE-NNE, EW-trending, SN-trending and NW, with NE and EW-trending mainly. It is characterized by four kinds of structural nature—reverse fault, normal fault, inverted fault, overthrust nappe fault and also four kinds of structural style—overthrust nappe, inversion structure, drape structure of buried hill, reverse drag anticlines.At the same time, the South Yellow Sea's continental strata is divided into four secondary structural units—Yantai Depression, Laoshan Uplift, Qingdao Depression, and Wunansha Uplift. Compared to the marine strata, it has only three kinds of structural system—NE, NW and EW-trending. In these depressions, there are tree kinds of structural character—normal fault, reverse fault and inverted fault, meanwhile it also shows five types of structural assemblage, which are mainly extensional structures such as tension fault and normal fault groups.The South Yellow Sea Basin has experienced six major stages of tectonic evolutio—Sinian-middle Ordovician plate expansion, late Ordovician-Silurian plate convergence, middle Devonian-middle Triassic stable platform, late Triassic-early Cretaceous intracontinental extrusion uplift, late Cretaceous-Paleogene intracontinental fault, Paleogene-Quaternary intracontinental downwarped basin.