西藏岗巴西山晚白垩世—早古近纪有孔虫生物地层

发布时间：2019-03-29 19:42

【摘要】：目前,我们对东特提斯西藏地区晚白垩世-早古近纪底栖大有孔虫的认识仍然较少。通过对西藏浅海沉积中的底栖大有孔虫化石的分析和总结,本论文初步建立了一整套较高精度的晚白垩-早古近纪的有孔虫生物地层。(1)通过对西藏特提斯晚白垩纪世-早古近纪海相地层及其所含的底栖有孔虫的研究,识别出四个沉积阶段13个有孔虫生物带:(1)第一个沉积阶段(Coniacian期到Maastrichtian期),大部分形成于较深的内部-外部浅海环境,具有龙脊的浮游有孔虫是这一阶段动物群(TLK1)的主要组成;(2)第二个沉积阶段(Maastrichtian末期),浮游有孔虫几乎被礁前动物群(主要以Lepidorbitoides、Omphalocyclus和Orbitoides种类为主,TLK2)完全替代;(3)第三个沉积阶段(古新世早期),在白垩纪末期的全球性大灭绝之后,古新世时全球气温开始变暖,浅海礁体环境开始重新出现,更适宜在温暖浅海环境下生存的底栖大有孔虫在这一时期非常繁盛,因此古新世的底栖动物群主要有小个体miliolids和rotaliids底栖有孔虫(如Ranikothalia、Daviesina和Lockhartia等,TP1-4);(4)第四个沉积阶段(古新世晚期-始新世早期),浅海礁体环境主要由温水底栖有孔虫种类(如Alveolina及Assilina,TP5-11)为主。(2)结合前人研究提出的碳同位素偏移数据(CIE),在本文划分的有孔虫生物地层基础上,将P-E界线确定在TP6中部位置,对应着标准底栖有孔虫化石带5(SBZ5)上部位置,而不是其他学者认为的SBZ4-SBZ5交界位置。(3)结合对东、西特提斯底栖大有孔虫生物带目前的研究成果,认为Alveolina等底栖大有孔虫在东特提斯的出现时间比西特提斯晚了大约1Ma,这也支持了底栖大有孔虫由西向东迁移的推测。(4)本次研究重新建立了东特提斯晚白垩世-早古近纪底栖大有孔虫生物地层序列,同时也在东特提斯生物带与西特提斯浅海底栖生物带(SBZs)之间建立了清晰的联系。基于有孔虫生物地层重新确定了岗巴西山剖面中的P-E界线。
[Abstract]:At present, our understanding of the late Cretaceous-early Paleogene benthic foraminifera in the Tibet area of East Tethys is still less than that of the late Cretaceous-early Paleogene foraminifera. Based on the analysis and summary of the benthic foraminifera fossils in the shallow sea sediments of Tibet, A set of high precision foraminifera biostratigraphy from late Cretaceous to early Paleogene has been established in this paper. (1) the marine strata and their benthic foraminifera contained in Tethys, Tibet, are studied in this paper. Thirteen foraminifera biota were identified in four sedimentary stages: (1) the first sedimentary stage (Coniacian to Maastrichtian), most of which was formed in a deeper inner-outer shallow sea environment; The zooplankton foraminifera with dragon ridges is the main component of the fauna (TLK1) at this stage. (2) in the second sedimentary stage (end of Maastrichtian), phytoplankton foraminifera was almost replaced by prereef fauna (mainly Lepidorbitoides,Omphalocyclus and Orbitoides species, TLK2). (3) in the third sedimentary stage (early Paleocene), after the global extinction at the end of the Cretaceous, the global temperature began to warm in the Paleocene, and the shallow reef environment began to re-emerge. Benthic foraminifera, which are more suitable for living in warm shallow sea environment, are very prosperous in this period. Therefore, the Paleocene benthic fauna mainly consists of miliolids and rotaliids benthic foraminifera (such as Ranikothalia,Daviesina and Lockhartia, TP1-4). (4) in the fourth sedimentary stage (late Paleocene-early Eocene), the shallow reef environment consists mainly of warm-water benthic foraminifera species (such as Alveolina and Assilina,). (2) on the basis of the foraminifera biostratigraphy in this paper, based on the carbon isotope migration data (CIE), the TP5-11 boundary is located in the middle part of the TP6. It corresponds to the upper position of the standard benthic foraminiferal fossil zone 5 (SBZ5) rather than the SBZ4-SBZ5 junction position considered by other scholars. (3) combined with the present research results of the macroforaminiferal benthic foraminifera belt in eastern and western Tethys, It is believed that the occurrence of benthic foraminifera such as Alveolina in East Tethys was about 1 Maa later than that of Seettis. This also supports the hypothesis that benthic large foraminifera migrate from west to east. (4) this study reestablished the late Cretaceous-early Paleogene macroforaminifera biostratigraphic sequence of East Tethys. A clear link has also been established between the East Tethys belt and the Seettis shallow benthic zone (SBZs). Based on the foraminifera biostratigraphy, the P _ (?) E boundary in the Gangbaishan profile has been redefined.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q915

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