Continental weathering following a Cryogenian glaciation: Evidence from calcium and magnesium isotopes
Continental weathering following a Cryogenian glaciation: Evidence from calcium and magnesium isotopes
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DOI：
10.1016/j.epsl.2014.03.048
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发表时间：
2014-06
影响因子：
5.3
通讯作者：
S. Kasemann;P. P. V. Strandmann-P.;A. Prave;A. Fallick;T. Elliott;K. Hoffmann
中科院分区：
文献类型：
--
作者：
S. Kasemann;P. P. V. Strandmann-P.;A. Prave;A. Fallick;T. Elliott;K. Hoffmann
根据硼同位素测量结果推断，在较年轻的Cryogenian冰川作用的极端环境条件下，发生了明显的海洋酸化事件，大气中二氧化碳浓度升高。钙和镁同位素分析为这段时间发生的过程提供了更多的见解。来自纳米比亚新元古代剖面的数据表明，冰川作用结束后，大陆风化通量从碳酸盐和硅酸盐混合特征过渡到硅酸盐为主。加上帽白云岩中原生白云岩形成的影响，这导致海洋脱离酸化状态，并在气候改善后恢复到较高的pH值。在整个大陆边缘的南部刚果克拉通陆棚的地层同位素变化的幅度的差异点修改和放大的全球信号，这需要加以考虑，以避免高估全球化学风化通量的本地影响。
A marked ocean acidification event and elevated atmospheric carbon dioxide concentrations following the extreme environmental conditions of the younger Cryogenian glaciation have been inferred from boron isotope measurements. Calcium and magnesium isotope analyses offer additional insights into the processes occurring during this time. Data from Neoproterozoic sections in Namibia indicate that following the end of glaciation the continental weathering flux transitioned from being of mixed carbonate and silicate character to a silicate-dominated one. Combined with the effects of primary dolomite formation in the cap dolostones, this caused the ocean to depart from a state of acidification and return to higher pH after climatic amelioration. Differences in the magnitude of stratigraphic isotopic changes across the continental margin of the southern Congo craton shelf point to local influences modifying and amplifying the global signal, which need to be considered in order to avoid overestimation of the worldwide chemical weathering flux.