Abstract: Based on the optical dating and paleomagnetic testing results,we make a chronostratigraphic research of Huanghua depression and Cangxian uplift which are two tectonic units of Tianjin area.In this paper,we establish a Quaternary stratigraphic section and make a new division of the Quaternary strata.The result shows that the two tectonic units have similar sedimentation histories,but many differences exist.On the one hand,both units have received transgression since the Quaternary and some marine strata formed to various extents,which indicates different transgression sedimentation histories between them;on the other hand,the Quaternary stratigraphic sequences of the two units are greatly different,indicating different sedimentation histories,and consequently,the type and thickness of sediments are obviously different,so they belong to different sedimentary units.The study also shows the depths of bottom interfaces of Holocene,upper Pleistocene and middle Pleistocene as 19m,45m and 103m,respectively in hole BZ1 in Huanghua depression and 13m,30m and 56m respectively in hole BZ2 and hole TN3 in Cangxian uplift.The depth of bottom interface of the Quaternary is about 162m,much smaller than the result of the previous Quaternary strata division.

Key words: Quaternary strata, OSL dating, magnetostratigraphy, marine strata, chronostratigraphic section

摘要： 通过钻孔岩心光释光测年与古地磁测试,对天津地区黄骅坳陷和沧县隆起两个构造单元的年代地层进行了研究,对区内第四纪分层界线重新进行了划分,建立了本区第四纪年代地层剖面。黄骅坳陷和沧县隆起两个构造单元的沉积发展历史具有一定相似性,同时还存在较大的差异。主要表现在:第四纪以来,黄骅坳陷和沧县隆起均有海侵发生,沉积一些海相地层,但是其发育程度不同,反映两个构造单元有着差异较大的海侵历史;二者在第四纪年代地层序列上存在较大差异,形成的相应沉积物的类型和厚度明显不同,为两个不同的第四纪沉积单元;天津地区原来第四系内部的分层界线为:Q_h埋深20m,Q_p³为70～80m,Q_p²为180～210m,Q_p¹为400m。研究表明,天津地区的第四系在黄骅坳陷和沧县隆起上明显不同:黄骅坳陷中的全新统、更新统上段及中段底界深度约分别为19,45,103m,第四系底界深度>200m;沧县隆起上的全新统、更新统上段及中段底界深度分别为13,30,56m,而第四系底界埋深为162m左右,远远浅于原来第四系分层的界线。

关键词: 第四纪地层, 光释光测年, 磁性地层学, 海相地层, 年代地层剖面