论文部分内容阅读
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
Biota, sediments and organic geochemical changes show that there is a clear response to the Pliocene-Pliocene (P / E) global event in the Tingri (low-latitude Eastern Tethys low-latitude) region of southern Tibet: The genera and species extinction rates of the foraminifer fauna at the top of the Zongzongpu Formation are 87% and 94% respectively, while the foraminifera at the bottom of the Eocene Yingpu Formation is 80% and 69% respectively. The lithofacies transform from thin to middle layer to thick layer and massive limestone, and the argillaceous content increases. The parameters of typical biomarkers change obviously, the Pr / 17 ratio increases from 0.365 to 0.86 on average, Ph / 18 changed from 0.56 to 0.92, β / 17 increased sharply from 12.84 to 12 3.17, and γ / 17 changed from 2.46 to 2 9.5. According to the lithofacies distribution and contact relationship in Tibet and its adjacent areas, it is considered that the response of this global geological event may be an ancient oceanic event in the study area and may be caused by the change of ocean circulation