(Table 1) Cd/Ca and Mn/Ca ratios of benthic foraminifera from DSDP Hole 30-289

The late Miocene carbon shift (~6.2 Myr) -a 0.5-1.0 per mil, d13C decrease in benthic and planktonic foraminifera- has been ascribed to changes in global inventory, deep-ocean circulation, and/or productivity. Cadmium, d13C, and nutrients in the ocean are linked; comparison of d13C and Cd/Ca yields circulation and chemical inventory information not available from either alone. We determined Cd/Ca ratios in late Miocene benthic foraminifera from DSDP Site 289. Results include: (1) late Miocene Pacific Cd/Ca values fall between those of late Quaternary Atlantic and Pacific benthic foraminifera; (2) there are no systematic Cd/Ca offsets between Cibicidoides kullenbergi, Cibicidoides wuellerstorfi and Uvigerina spp.; and (3) there is a very slight Cd/Ca change coincident with d13C. Cd/Ca, slightly higher in younger, isotopically lighter samples, exhibits a smaller increase than predicted if circulation were the primary cause of the carbon shift. The carbon shift may have been due to a long-term shift in the steady-state carbon isotope input or to a change in the sedimentation of organic carbon relative to calcium carbonate.晚中新世碳位移事件（约6.2百万年）——表现为底栖有孔虫与浮游有孔虫的δ¹³C（d13C）下降0.5~1.0千分比——被归因于全球碳储库变化、深海环流改变以及/或海洋初级生产力变动。海洋中的镉（Cd）、δ¹³C与营养盐三者存在内在关联；对比δ¹³C与镉钙比（Cd/Ca），可获得单独依靠任一指标无法获取的环流与化学储库信息。我们对深海钻探计划（Deep Sea Drilling Project, DSDP）289站位的晚中新世底栖有孔虫的Cd/Ca比值进行了测定，结果如下：（1）晚中新世太平洋的Cd/Ca数值介于晚第四纪大西洋与太平洋底栖有孔虫的Cd/Ca数值之间；（2）库勒贝格拟卷包虫（Cibicidoides kullenbergi）、武尔斯特福拟卷包虫（Cibicidoides wuellerstorfi）与优弯柱虫属（Uvigerina spp.）之间不存在系统性的Cd/Ca偏移；（3）存在与δ¹³C变化同步的极微弱Cd/Ca变动。年轻样品（同位素值更轻）中的Cd/Ca略高，若环流是本次碳位移的主要成因，则Cd/Ca的增幅应大于实际观测值。本次碳位移可能源于稳态碳同位素输入的长期偏移，或是有机碳相对于碳酸钙的沉积作用发生了改变。