【摘要】 生物群、沉积物和有机地球化学变化显示 ,古新统—始新统 (P/ E)界线全球事件在西藏南部定日 (东特提斯残留海低纬度浅水 )地区存在明显响应 :古新统宗浦组顶部有孔虫动物群的属、种绝灭率分别为 87%和 94% ,始新统遮普惹组底部有孔虫属、种新生率分别达 80 %和 6 9% ;岩层以 (生物滩相 )薄—中层向厚层—块状生物灰岩转化 ,泥质含量增加 ;典型生物标志化合物参数变化明显 ,Pr/ 17比值平均从 0 .36 5增加到 0 .86 ,Ph/ 18由 0 .5 6变为0 .92 ,β/ 17由 12 .843剧增到 12 3.17,γ/ 17由 2 .46突变为 2 9.5。结合西藏及邻区岩相分布、接触关系后认为 ,这种全球地质事件的响应在研究区可能是一种古海洋事件 ,可能由大洋环流 (古水团 )变化引起更多还原

【Abstract】 The exact boundary between Paleocene and Eocene,well exposed at Gongzha,northwestern flank of the Zhepure Shan syncline,west to Tingri is determined by benthic foraminiferal assemblages.There is an obvious replacement of Lockhartia community ranging from units 13 to 16 by Alveolina community in units 17～19.Most of the species in the Lockhartia community disappear in the Alveolina community,and ca.70% new species occur in the later community.A sedimentary response can be observed at the boundary of the P/E.The latest Paleocene units 13～16 are dominated by nodular limestone and thin wackstone less than 15 cm in single layer thickness with 5%～10% of clay,and above the boundary,the earliest Eocene units 17～19 are composed of thick blocky wackstone and packstone with clay less than 1%.Some organic geochemical data also provide clues for analysis of the P/E event.Parameters of biomarkers extensively support the idea. For example,Pr/17(pristane n-C17),Ph/18(phytane n-C18),β/17(β-carotane n-C17) and γ/17 (γ-carotane n-C17)increase simultaneously from units 14～16 to units 17～19.The sharp increase of the parameters to great degree is the result of redox condition changes.Organic elements and their relations N,C,N/H and N/O are also distinctly different beneath and above the boundary of the P/E although the causes are not available.From the response of biota,sediment and biomarker in Tingri,southern Tibet,we suppose that it could result from changes of ocean water masses that led to the geologic event at the turnover of the P/E in the Tibetan Tethys Himalayas,and caused the change of aerobic in latest Paleocene to the quasi-,anaerobic environment in the earliest Eocene in southern Tibetan Sea.更多还原