南黄海盆地基底及海相中、古生界地层分布特征

Basement structure and distribution of Mesozoic-Paleozoic marine strata in the South Yellow Sea basin

南黄海盆地是大型海相中、古生界和陆相中、新生界两期叠合型盆地,本文根据最新地震资料结合钻井资料及与海陆地质资料的对比研究对盆地内地震层序进行了划分,得到了陆相中、新生界盆地基底即中、古生界海相盆地的顶界埋深、三叠系和上二叠统的残留厚度,推断了陆相层基底地层分布,并根据磁力异常资料推测了海相中、古生界盆地结晶基底埋深,推断了海相中、古生界整体残留情况.下三叠统青龙组和上二叠大隆及龙潭组在南黄海盆地南部坳陷及勿南沙隆起广泛存在,而在北部坳陷的分布则狭窄,中部隆起则由于隆起和剥蚀作用导致这两套地层几乎没有残余.对中-古生界海相盆地和中-新生界陆相盆地的基底特征进行了比较,认为海相中、古生界在南黄海地区区域性存在,海相层厚度分布特征受基底起伏控制,同时受到印支板块运动的影响,中部隆起区是海相中、古生界比较稳定的地区.下古生界可能在南黄海盆地广泛分布,但受资料限制,还难以获知其残余地层的特征.

The South Yellow Sea basin is a large superposed basin composed of a Paleozoic- Mesozoic marine sedimentary basin and Mesozoic-Cenozoic terringenous sedimentary basin. The structure and stratigraphic distribution of the lower crystal basement and the upper folded basement of the two kinds of basins are discussed 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 Triassic Qinglong limestone and upper Permian strata is also analyzed in order 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 sequence in the northern depression is very limited; in the central uplift, few are left due to uplift and denudation. At present, the residual thickness of the lower Paleozoic remains unknown due to limited data.