苏北盆地晚白垩世-古新世海侵湖泊的证据及其地质意义

通过对苏北盆地钻井岩心分析研究总结得出，在晚白垩世、古新世苏北盆地曾与海相通，并遭受海侵影响。海侵的原因，可能是从晚白垩世晚期起，中国东部的地应力条件以引张力占优势，并在华北—渤海湾、苏北—南黄海和东海陆架区，发育了一系列为早第三纪巨厚沉积物所充填的半地堑箕状盆地，海水由东海向黄海海侵，造成陆架上箕状盆地在短时期内与海水相通。苏北盆地在晚白垩世泰州组—古新世阜宁组沉积形成了以全盆地阜二段、阜四段为主，局部泰二段的富含介形虫的暗色泥岩，成为该盆地的主力烃源岩。古生物以及岩矿、地球化学等方面的证据可以确定苏北盆地晚白垩世—古新世发育的湖盆环境可统称“近海湖泊”或将海侵层段称“海侵湖泊”，而至始新世戴南和三垛组沉积时则可统称内陆湖泊和河流冲积平原环境。通过对苏北盆地晚白垩世—古新世海侵湖泊的确切与充分的认识分析，不仅对苏北盆地晚白垩世—古新世时期的湖盆古地理重建，而且对烃源岩的发育与分布以及生油气潜力评价都具有重要的意义。

Evidence of Transgression Lake of Subei Basin During Late Cretaceous and Paleocene Epoch and Its Geological Significance

Based on the analysis of core of Subei basin during late Cretaceous and Paleocene Epoch, the authors conclude that Subei Basin was linked with the sea and the deposit was affected by transgression. The causes of marine transgression may be the tension power have predominated the ground stress condition of the east China and develop a series of halfgraben like basin which was filled by huge thick sediment of early Tertiary in shelf of Huabei Bohai gulf , Subei south yellow sea and East China sea. Consequently, seawater transgresses from East China Sea to yellow sea and connects half graben like basin on the shelf and sea during short period. During the sediment of late Cretaceous Taizhou Formation and Paleocene Epoch Funing Formation, Subei Basin have formed dark shale containing lots of ostracoda that include predominated whole basin E1f2 Formation and E1f4 Formation and local K2t2 Formation, which have become main source rocks of the basin. The evidences of paleontology, minerals in rocks and geochemistry can ascertain the environment of lake basin which develops during late Cretaceous and Paleocene Epoch. This environment was generally designated "near sea lake basin" or the layer and member that was transgressed by sea was called "transgression lake basin", whereas, which was generally called inland lake and river alluvium plain during sediment of Eocene Dainan Formation and Sanduo Formation. Based on the analysis and sufficiency cognition of Transgression Lake of late Cretaceous and Paleocene Epoch of Subei Basin, the research is important to not only paleogeographic reconstruction of Subei basin during late Cretaceous and Paleocene Epoch but also the comment to make upon development and distribution of the source rocks and potential of oil and gas generation.