上新世以来苏北盆地与长江三角洲构造沉降史分析

Tectonic Subsidence Analysis of Subei Basin and Yangtze Delta from the Pliocene

利用回剥分析定量恢复了上新世以来苏北盆地与长江三角洲的构造沉降速率,并对比分析了两者的沉降特征,同时探讨了与青藏高原隆升的响应关系。研究发现,上新世以来苏北盆地呈现缓慢沉降的特点,而长江三角洲则表现为"间歇式"沉降,出现了4次快速沉降阶段(Ⅰ-Ⅳ幕),且速率较苏北盆地高,表明沉降中心由北向南逐渐转移。长江三角洲的构造沉降过程与青藏高原隆升具有很好的响应关系。这种"跷跷板"的构造营力,也引导了长江最终东流入海。两盆地差异沉降表明长江可能最早于苏北入海,三峡贯通的更早记录应该在苏北盆地,而长江三角洲则记录了贯通年龄的一个下限。

Based on several sediment cores, back-stripping analysis is used to recover the tectonic subsid- ence rates in the Subei Basin and Yangtze Delta from the Pliocene. Results revealed that the Subei Basin underwent a slow trend of tectonic subsidence while the Yangtze Delta showed four intermittent subsidence phases （stages of I-Ⅳ）, with higher rate than that of the Subei Basin. This study also demonstrated that the subsidence center had shifted from the north of the Subei Basin to the south of the Yangtze Delta in the Plio-Quaternary. The close correlation between the tectonic subsidence of the Yangtze Delta and the uplift of Tibetan Plateau since the Late Cenozoic was witnessed. This ＇topographic reversal＇ in the Late Cenozo- ic is also believed to have diverted the Yangtze River to flow east. The study also proposed that the con- nection of Yangtze River into the sea should be earlier in the Subei Basin than the Yangtze Delta.