Abstract. We have measured Cd / Ca ratios of several benthic foraminiferal species and studied benthic foraminiferal assemblages on two cores from the northern Indian Ocean (Arabian Sea and northern Bay of Bengal, BoB), in order to reconstruct variations in intermediate water circulation and paleo-nutrient content since the last deglaciation. Intermediate water Cd_w records estimated from the benthic Cd / Ca reflect past changes in surface productivity and/or intermediate-bottom water ventilation. The benthic foraminiferal assemblages are consistent with the geochemical data. These results suggest that during the last deglaciation, the Heinrich Stadial 1 and Younger Dryas (HS1 and YD, respectively) millennial-scale events were marked by a decrease in Cd_w values, indicating an enhanced ventilation of intermediate-bottom water masses. Benthic foraminifer assemblages indicate that surface primary productivity was low during the early Holocene (from 10 to 6 cal kyr BP), resulting in low intermediate water Cd_w at both sites. From ~ 5.2 to 2.4 cal kyr BP, the benthic foraminiferal assemblages indicate meso- to eutrophic intermediate water conditions, which correspond to high surface productivity. This is consistent with a significant increase in the intermediate water Cd_w in the southeastern Arabian Sea and the northeastern BoB. The comparison of intermediate water Cd_w records with previous reconstructions of past Indian monsoon evolution during the Holocene suggests a direct control of intermediate water Cd_w by monsoon-induced changes in upper water stratification and surface primary productivity.

中文翻译：

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自上次冰消期以来北印度洋生产力和中间环流的变化：底栖有孔虫Cd / thinsp; Ca记录和底栖组合分析的新见解

摘要。我们测量了几种底栖有孔虫物种的Cd / Ca比值，并研究了北印度洋（阿拉伯海和孟加拉北部湾，BoB）两个岩心上的底栖有孔虫组合，以重建中间水循环和古营养素的变化。自上次冰消以来的含量。根据底栖Cd / Ca估算的中间水Cd _w记录反映了过去地表生产力和/或中底水通风的变化。底栖有孔虫组合与地球化学数据一致。这些结果表明，在最后一次冰消期间，Heinrich Stadial 1和Younger Dryas（分别为HS1和YD）的千年尺度事件以Cd _w的降低为标志。值，表明中底水团的通风增强。底栖有孔虫的组合表明，在全新世早期（从10到6千卡比BP），表面初级生产力较低，导致两个位置的中间水Cd _w较低。从约5.2到2.4 cal Kyr BP，底栖有孔虫的组合表明中等至富营养的中间水条件，这对应于高地表生产力。这与阿拉伯海东南部和东北BoB中中间水Cd _w的显着增加是一致的。全新世时期中间水Cd _w记录与以前印度季风演化的先前重建的比较表明，中间水Cd的直接控制_瓦特通过在上部水分层和表面初级生产力季风诱导的变化。