摘要
渤海湾盆地辽西凹陷古近纪中晚期为深水湖泊环境,形成了特殊的古生物化石组合.本文通过研究区钻遇古近系钻井进行详细的古生物对比研究,归纳出该地区微体化石组合特征,建立了5个孢粉藻类化石组合及5个介形类化石组合.在辽西凹陷西部和西北部沙河街组见较深水、叠覆明显的近梯形介形类化石Candona sagmaformis、C.postabscissa和具膜管的藻类化石Hystrichosphaeridium tubiferum、Membranilamacia,研究区东营组广泛见深水介形类化石Tianjinia fulgida、Bohaicytliere sp、Parabohainia elliptica等.这些化石特征揭示了沙河街组至东营组沉积时期深水沉积中心范围逐步扩大,最终沉积中心连成一体.同时,通过大量古生物化石和岩性对比,得出辽西凹陷在沙河街组二段沉积时,存在较大范围的沉积间断,研究区内广泛发育沙河街组三段上亚段.这些认识为该地区古近系地层的划分对比及沉积环境研究提供了有利证据.
Abstract
The deep-water environment in lakes of the middle and late Paleogene in the Liaoxi sag,Bohai Bay Basin,formed a special group of paleontological fossils.In this study,we characterized the microfossil assem-blages through investigating the paleontological drilling data in this study area.Five fossil assemblages of pollen algae and five mesomorphic fossil assemblages were established.In the western and northwestern Shahejie For-mation,distinct near trapezoidal mesomorph fossils Candona sagmaformis,C.postabscissa,and membrane tube algae fossils Hystrichosphaeridium tubiferidium tubiferi and Membranilarnacia originally formed in deep-water were observed.Moreover,mesomorph fossils Tianjinia fiulgida,Bohaicythere sp,Parabohainia elliptica,and others formed in deep-water were widely observed in Dongying Formation.These fossil signatures indicate that the range of sedimentary center in deep water expanded gradually from Shahejie Formation to Dongying Forma-tion,and it connected with the sedimentary centers of the Liaozhong depression in the end.Meanwhile,compar-ison study of a large number of paleontological fossils and their rock lithology,we concluded that the Liaoxi sag and the low convex zone of Liaoxi sag had a large range of sedimentary breaks when deposited in the second sec-tion of Shahejie Formation.Also,the upper subsection of the third section of Shahejie Formation is widely de-veloped.This study provides a strong evidence for the division and comparison of the Paleogene strata in this re-gion,and meanwhile this study enriched the relevant studies on sedimentary environment.
基金项目
国家科技重大专项(2016ZX05024003-002)
维普
万方数据