Elemental abundances in marine carbonates from ODP Leg 115 holes (Table 1)

We subjected 18 carbonate samples <1-46 Ma in age from Holes 706A, 707A, 708A, 709C, 710A, and 711A on or near the Mascarene Plateau and Madingley Rise and from Holes 712A, 713A, and 716A on or near the Chagos Bank-Maldives Ridge to instrumental neutron activation analysis to measure 32 major, minor, and trace elements and to determine the Ce anomalies (CeA*) in the carbonates relative to NASC (North American Shale Composite). Five carbonates, 32-46 Ma, yielded an average CeA* value of 0.14 ± 0.05, corrected for small (0.1%-1.8%) detrital clay particulates. This CeA* value is considered to represent the inferred CeA value in the western Indian Ocean during the 32-46-Ma interval and compares to an average CeA value of 0.05 ± 0.02 in the Pacific Ocean during the past ~35 Ma and from 93 to 97 Ma. These inferred CeA values are consistent with the Ce redox formulation proposed previously by the authors, which indirectly relates the CeA of seawater to the pH of the mixed layer.
The higher CeA* values of 0.23-0.66 in 11 carbonates, <1-30 Ma, indicate an inhibition of Ce + 3 oxidation to Ce(OH)4 in seawater during this interval. This observation is consistent with an enhanced transport of decayed organic debris into the Indian Ocean from the Himalayan Mountains, thereby providing a more reducing seawater environment. The postulated prominence of the Himalayas at ~30 Ma is consistent with the ODP Leg 116 observations that the voluminous sedimentation rates in the eastern Indian Ocean from the Bengal Fan existed for the past >24 Ma. An accelerated rise of the Himalayas may have commenced ~33-35 Ma.

我们对马斯卡林海台（Mascarene Plateau）及马丁利海岭（Madingley Rise）附近的706A、707A、708A、709C、710A、711A钻孔，以及查戈斯滩-马尔代夫海岭（Chagos Bank-Maldives Ridge）附近的712A、713A、716A钻孔的18件年龄介于1 Ma至46 Ma的碳酸盐样品，开展了仪器中子活化分析（instrumental neutron activation analysis），以测定其中32种常量、次要及痕量元素含量，并计算碳酸盐相对于北美页岩标准（North American Shale Composite, NASC）的铈异常值（Ce anomalies, CeA*）。其中5件年龄为32 Ma至46 Ma的碳酸盐样品，经校正0.1%~1.8%的碎屑黏土颗粒干扰后，其CeA*平均值为0.14 ± 0.05。该CeA*值被认为代表了32 Ma至46 Ma期间西印度洋的推断铈异常值，可与过去约35 Ma以来及93 Ma至97 Ma期间太平洋的平均铈异常值（0.05 ± 0.02）进行对比。上述推断的铈异常值与作者此前提出的铈氧化还原模型一致，该模型将海水铈异常与混合层pH值间接关联起来。
另有11件年龄介于1 Ma至30 Ma的碳酸盐样品，其CeA*值介于0.23~0.66，偏高的CeA*值表明该时段海水中Ce³+被氧化为Ce(OH)₄的过程受到抑制。这一观测结果与喜马拉雅山脉向印度洋输入的腐解有机碎屑增多的推论相符，即当时印度洋海水环境还原性更强。约30 Ma时喜马拉雅山脉的隆起幅度达到峰值的假设，与大洋钻探计划（Ocean Drilling Program, ODP）第116航次的观测结果一致：孟加拉扇在过去24 Ma以来的沉积速率极高。喜马拉雅山脉的加速抬升或始于约33 Ma至35 Ma期间。