【作者】 王曦；

【导师】 万晓樵；

【作者基本信息】 中国地质大学（北京） ， 海洋地质， 2006， 硕士

【摘要】 随着深海钻探计划(DSDP)和大洋钻探计划(ODP)的开展,在古海洋学领域已经取得了许多重大发现。古近纪古新世与始新世(P/E)界线间的地质事件的发现便是其重要成果之一。西藏南部岗巴地区发育有良好的海相界线地层。本文对剖面各个层位生物群,界线附近的碳、氧、锶稳定同位素以及磁化率进行了研究,研究成果显示,全球界线事件在西藏南部岗巴地区具有明显的影响。古新统宗浦组顶部底栖有孔虫动物群阶段性绝灭,总灭绝率为69%,与世界其他深海地区相对应。始新统遮普惹组底部有孔虫逐渐复苏,除两种为古新世的残存类型外,始新世生物组合全为新的属种,并呈现三个复苏阶段。根据分析,PETM事件的发生造成海水温度的升高,使生活环境发生改变。该事件发生很突然,持续时间很短,在突发事件中有孔虫不能适应新的环境,从而造成大量绝灭。事件发生后,海水温度逐步恢复正常,新的有孔虫的属种开始出现并大量繁殖,有孔虫又进入繁盛时代。碳稳定同位素表现为三期负向偏移,并在界线处出现约4‰的负向偏移。这一异常与全球碳稳定同位素事件表现一致。PETM事件的δ13C明显负偏移可从海洋环境的变化得到解释。由于成岩作用的影响,氧稳定同位素的变化与全球极端气候事件不太一致。锶同位素在界线位置没有明显的变化,而明显的峰值出现在界线之上,初步推断是与陆源物质的输入有关。这种变化与全球53Ma出现的锶同位素变化相对应。磁化率曲线在界线附近表现平稳,而在界线之上2m处出现一个很明显的波动。这一结果可能是由于岩性的变化以及降水或者是气候的变化造成的。西藏南部岗巴地区宗浦剖面P/E界线附近生物群、同位素、磁化率参数的明显变化,表明研究区对应的地质事件是客观存在的,也说明P/E界线全球地质事件同样发生在东特提斯低纬度浅海地区。西藏南部(特提斯低纬度浅海环境)受全球地质事件的影响,在古新世与始新世界线时期出现明显的气候变化。全球深海温度增高在浅海环境具有相同表现。只是影响时间较长。更多还原

【Abstract】 With the development of DSDP and ODP, a lot of important results have beenachieved in palaeoceanography. One of them is the geologic event at thePaleocene/Eocene boundary (P/E). A marine boundary succession is well preserved inthe Gamba region of southern Tibet. The research on micro-fauna and carbon, oxygen,strontium isotopes and magnetic susceptibility reveals that the signals of globalPaleocene/Eocene boundary event are well recorded in the Gamba region. Thebenthic foraminifera were extinguished stepwise toward the top of the PaleoceneZongpu Formation, with a general extinction rate of 69%. Overturn of foraminiferaoccurs at the P/E boundary that is indicated by the extinction of genus Miscellanea.The recovery of the faunal happened gradually upward from the bottom of the EoceneZhepure Formation. Except 12 species were survived from the Paleocene, all other 56genera are new types of Eocene and present three recovery stages. According to theanalysis, PETM event caused seawater temperature rising and environment change.This event happened abruptly and lasted a short time, benthic foraminifera cannot fitfor it and begin to extinct. After that, the temperature return to normal, with newgenus appeared. A clear negative Carbon isotope shift of -4‰ occurs at the boundary.It is well correlated with standard isotopic shift in the world. The changes of the seaenvironment can help us to explain this kind of phenomenon. But the changes ofoxygen isotope are not consistent with event. The strontium isotopic shift is notobvious at the boundary, but an important peak appears above the boundary that ismatched with the 53ma level. Magnetic susceptibility change is obscure at theboundary but a sharp change of magnetic susceptibility clearly appears at two metersabove the boundary. All above significant changes imply that the Tethys-Himalayanarea was affected by the Paleocene/Eocene Thermal Maximum (PETM). Temperaturewarming in deep oceans also occurred in shallow marine sequence but with expandedduration.更多还原