【摘要】 喜马拉雅-青藏高原的构造隆升所引起的硅酸盐风化增强长期以来被认为是新生代大气二氧化碳浓度降低和全球变冷的主要原因.然而,由于缺乏喜马拉雅-青藏高原地区可靠的风化通量重建,这一“隆升-风化”假说迄今仍有待检验.本文利用孟加拉湾大洋钻探计划（ODP） 758站岩芯沉积物浮游有孔虫放射性钕同位素重建了晚始新世以来印度洋北部海水钕同位素组成的长期演化,并将其与印度洋中部海水钕同位素记录进行对比而剔除印度洋水团影响,其二者差值(Δε_Nd)的变化趋势可指示来自南亚的大陆风化输入对印度洋的贡献.结果显示Δε_Nd呈现长期增长的趋势,从而提供了晚新生代南亚风化长期增强的关键证据.孟加拉湾有孔虫ε_Nd记录的南亚风化输入增强的阶段与喜马拉雅造山带主要的构造隆升期和全球气候转型相吻合,暗示了南亚大陆特别是喜马拉雅地区的构造隆升和硅酸盐风化增强对晚新生代全球变冷有着重要贡献.更多还原

【Abstract】 Enhanced silicate weathering induced by the uplift of the Himalayan-Tibetan Plateau（HTP） has been considered as the major cause of pCO₂ decline and Cenozoic cooling.However,this hypothesis remains to be validated,largely due to the lack of a reliable reconstruction of the HTP weathering flux.Here,we present a 37-million-year record of the difference in the seawater radiogenic neodymium isotopic composition(Δε_Nd) of Ocean Drilling Program（ODP） sites and Fe-Mn crusts between the northern and central Indian Ocean,which indicates the contribution of regional weathering input from the South Asian continent to the Indian Ocean.The results show a long-term increase in Δε_Nd and thus provide the first critical evidence of enhanced South Asian weathering input since the late Eocene.The evolution coincided well with major pulses of surface uplift in the HTP and global climatic transitions.Our foraminiferal ε_Nd record suggests that tectonic uplift and silicate weathering in South Asia,especially in the Himalayas,might have played a significant role in the late Cenozoic cooling.更多还原