摘要
南黄海中部隆起是下扬子地块向海域的延伸,是当前海相盆地海域资源调查的潜力区。中部隆起自印支期以来经历多期构造隆升、挤压及剥蚀作用,显著影响了盆地油气资源的形成和分布。2016年底完钻的大陆架科学钻探CSDP-2井首次在中部隆起钻穿印支不整合面,该不整合面在中部隆起既是新近系-第四系底界,又是下三叠统灰岩的顶界,横向延伸平缓,上、下地层产状差异巨大,下伏地层具有强烈的挤压变形及逆冲推覆,呈现显著的角度不整合接触关系。本次研究基于泥岩声波时差法计算的印支面地层剥蚀量约为1200 m,镜质体反射率法计算的剥蚀量约为1400 m,与地层趋势面估算的剥蚀量基本一致。结合南黄海盆地演化过程分析,认为中部隆起大致于晚三叠世开始隆升,至晚白垩世期间经历快速剥蚀,并可能延续到渐新世末期。在当前南黄海盆地资源调查逐步转向中、古生界海相残留盆地之际,依托实际钻探资料进行印支不整合面研究及剥蚀量恢复对于恢复盆地构造-热演化史及评价油气资源等均具有重要的现实意义。
The central uplift of the South Yellow Sea(SYS) is an important potential area for basin resources exploration.The compressive deformation and denudation of the tectonic uplift since the Indosinian period are still unclear and have been a subject of active debate, though they may have significantly impacts on the formation and distribution of oil and gas resources in the basin. The CSDP-2 well(121°15′E, 34°33′N), supported and carried out by the Continental Scientific Drilling Project(CSDP) of China Geological Survey(CGS), was the exclusive deep exploratory well drilled in the central uplift of SYS. The depth of the Indosinian unconformity surface drilled by the CSDP-2 is 596 m. The seismic profiles calibrated by CSDP-2 show that the Indosinian unconformity is a regional strong reflectance interface between the Neogene-Quaternary unconsolidated sedimentary cover and the Lower Triassic limestone. As an integrated core-drilling well, it provide powerful data to study some fundamental geological events of this region. Integrated geophysical data and measured results of core samples can be used to estimate the eroded thickness. The denudation thickness calibrated by sonic-logging data and vitrinite reflectance is about 1200 m and 1400 m respectively, which is consistent with the analysis result from stratigraphic trend surface. The analysis of the evolution process of the SYS indicated that the central uplift underwent a prolonged denudation from the Middle-Late Cretaceous to the end of the Eocene. The study of Indosinian unconformity is of great practical significance for the restoration of the tectonic-thermal evolution history and the evaluation of oil and gas resources in the South Yellow Sea Basin(SYSB).