东经90°海岭的远洋沉积记录与晚新生代重大构造环境事件

PELAGIC SEDIMENTARY RECORDS OF THE NINETYEAST RIDGE AND THE LATE CENOZOIC IMPORTANT TECTONO-ENVIRONMENTAL EVENTS

东经 90°海岭的北部远洋型沉积记录是青藏高原隆升的远程监视器。文章应用有孔虫组合分析和壳体微量元素分析 ,结合相关的沉积学、地球化学、古地磁学和微体古生物学工作 ,对以ODP75 8钻孔为代表的 9Ma以来的沉积记录综合研讨 ,识别出对应于高原阶段隆升 (3 7～ 3 2Ma、0 .8～ 0 .6Ma、0 .17～ 0 .16Ma)的重大环境变化信号。文章还提出印度冬季季风强度是反映高原构造活动关键标志的观点。按照这种观点 ,海岭远洋记录提供的晚新生代最大环境转折时段位于 3.7～ 3.2Ma间。

The pelagic sedimentary records from the North of the Ninetyeast Ridge can be regarded as a tele-monitor for understanding the uplift of the Qinghai-Xizang (Tibetan) Plateau. Using the identification of foraminiferal assemblage and analysis of the foraminiferal test and combining the above results with the previous sedimentary, geochemical, paleomagnetic and micropaleontological data, we make an integrated discussion about the ridge records since 9Ma displayed typically by ODP758 site. Some significant signals of variable ocean environment, which response to the phased uplift of the plateau dating from 3.7Ma to 3.2Ma, 0.8Ma to 0.6Ma and 0.17Ma to 0.16Ma, can be obviously recognized in the records. We point out that the intensity of Indian winter monsoon is just a key symptom to mirror the tectonics of the plateau. On the basis of this point, the period marking the most important turn of environment during the Late Cenozoic shown by the ridge records has been found between 3.7Ma and 3.2Ma.