Basement Structure and Distribution of Mesozoic‐Paleozoic Marine Strata in the South Yellow Sea Basin

The South Yellow Sea basin is a large superposed basin composed of a Paleozoic-Mesozoic marine sedimentary basin and Mesozoic-Cenozoic terrigenous sedimentary basin. This work studied the structure and stratigraphic distribution of the lower crystal basement and the upper folded basement of the two kinds of basins based on integrated geological and geophysical data. New seismic data interpretation combined with drilling data and geological correlation between land and sea are used to identify the marine Paleozoic-Mesozoic stratigraphic sequence. The depth of the top surface of the marine Paleozoic-Mesozoic strata is determined by seismic interpretation; undulation of the bottom surface is derived by magnetic inversion. The residual thickness of the Triassic Qinglong limestone and the upper Permian strata is also analyzed to understand the distribution and structure features of the marine Paleozoic-Mesozoic strata. The thickness and distribution of the marine sequence are mainly controlled by the undulation of the basement, and also influenced greatly by the Indosinian movement. The thickness of the marine Paleozoic-Mesozoic strata is comparatively stable in the central uplift. The lower Triassic Qinglong formation and the upper Permian Dalong and Longtan formations are widely distributed in the southern depression and the Wunansha uplift of the South Yellow Sea basin, while the distribution of this succession in the northern depression is very limited; in the central uplift, little is are left due to uplift and denudation. At present, the residual thickness of the lower Paleozoic remains unknown due to limited data available.