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对深海钻探研究项目72号钻井区516号钻孔和516号钻孔的32个沉积物样品进行了仪器中子活化分析。测定了32个常量、少量和微量元素,在碳酸盐相中获得了Ce异常值,Ce~A≡Ce(观测)/Ce~*(La和Nd含量之间的内插值,相对于北美页岩混合样)=Ce(观测)/[1.144La(观测)+0.66Nd(观测)]。计算表明,Ce异常由0.8(80Ma)、0.68(67Ma)变化为0.3(56Ma)、0.27(39Ma)和0.12—0.43(平均为0.26)(15—0.3Ma)。在～55Ma观察到的Ce~A与在58Ma于沃尔维斯洋脊525A号钻孔海相碳酸盐中观察到的Ce~A变化相吻合。这些变化是由于南北大西洋通道的拓宽,里奥格兰德洋底高地的下沉或罗曼什断裂带的下沉使海水循环得到改善。Ce~A变化的最终驱动力与海水的pH值和P(?)_2(氧分压)有关,并且也与大洋底部水的全球循环以及来自河流或风成物质来源的外部陆源输入物质的搬运有关。
Instrumental neutron activation analysis was performed on 32 sediment samples from deep drilling project Drilling No. 516 and Drilling No. 516 in No.72 drilling area. 32 constants, minor and trace elements were determined, Ce anomalies were obtained in the carbonate phase, and Ce ~ A≡Ce (Observations) / Ce ~ * (interpolated values between La and Nd content, relative to North American pages Rock mixed) = Ce (observed) / [1.144La (observed) + 0.66Nd (observed)]. Calculations show that the anomalies of Ce vary from 0.8 (80Ma), 0.68 (67Ma) to 0.3 (56Ma), 0.27 (39Ma) and 0.12-0.43 (averaging 0.26) (15-0.3Ma). The Ce ~ A observed at -55 Ma coincided with a change in Ce ~ A observed in 58 Ma in 525A bore marine carbonate at Walvis Ridge. These changes are due to the broadening of the North-South Atlantic passage, the descent of the Rio Grande ocean floor or the subsidence of the Romansh fault zone, which improves the seawater cycle. The final driving force for Ce-A change is related to seawater pH and P (?) _2 (oxygen partial pressure) and also to the global circulation of oceanic bottom waters and the transport of external terrigenous input from rivers or sources of wind related.