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本文对南海西南次海盆IODP U1433站上中新统远洋粘土中的钙质超微化石生物地层学与属种组合作了较为详细研究。结果显示研究层位底部年龄在10.40-9.75 Ma之间,属于NN9带,向上共识别出8个钙质超微化石生物地层事件。依据生物地层框架、钙质超微化石总丰度与属种百分含量,发现西南次海盆在8.3-8 Ma以前处于上层海水分层性好,表层海水生产力较低的阶段;大约在8 Ma以后,生产力大幅增加。结合前人U1433站位物源研究结果,以及南海东亚季风强度变化史,作者认为钙质超微化石显示的生产力变化,与越南中部高地的抬升,以及东亚夏季风增强有关。
In this paper, the calcareous nannofossil biostratigraphy and genera assemblages in the Upper Miocene marine clay of IODP U1433 Southwest China Sea Basin are studied in detail. The results show that the bottom of the study horizon is between 10.40-9.75 Ma and belonged to the NN9 zone, up to which eight calcareous nannofossil biostratigraphic events were identified. Based on the biostratigraphy framework, the total abundance of calcareous microfossils and the percentage of genera of the species, it was found that the sub-sea basin in the southwest was well stratified in the upper strata before 8.3-8 Ma and had a low seawater productivity in about 8 Ma After that, productivity increased dramatically. Based on the provenance of previous U1433 stations and the history of monsoon intensities in the East China Sea in the South China Sea, the author believes that the productivity changes of calcareous nannofossils are related to the uplifting of the highlands in central Vietnam and the enhancement of the East Asian summer monsoon.