Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record
Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record
复制标题
了解与岩石记录中海洋酸化和碱度超调相关的 Ca 同位素信号
DOI：
10.1016/j.chemgeo.2020.119672
复制
发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Ridgwell, Andy
中科院分区：
文献类型：
--
作者：
Fantle, Matthew S.;Ridgwell, Andy
在这篇文章中，我们探讨了Ca同位素代用指标作为碳酸盐自生作用的指示剂的想法（即，沉积包内CaCO 3的沉积后沉淀）。由于形成和成岩环境之间的同位素分馏因子的强烈对比，Ca同位素有可能指纹碳酸盐自生作用时，它发生在海水-沉积物界面附近。我们证明，钙同位素是特别适用于探索海洋酸化事件，并可能海洋缺氧事件，并把我们的注意力集中在海洋酸化有关的古新世始新世热极大期（PETM）。我们提出了三个方案，不同的幅度和持续时间的碳通量，模拟使用地球系统模型的中间复杂性（cGENIE），我们使用cGENIE输出约束的1-D反应运输模型的上边界条件的自生和重结晶的沉积部分。沿着简单的混合计算，模型告知我们的假设，即自生碳酸盐引起的饱和状态超调解释最近发表的钙同位素记录，并可能散装碳酸盐记录在海洋缺氧事件（OAE）2的探索。我们的模拟表明分馏因子的变化不能解释PETM δ 44 Ca记录，我们提出了一个δ 44 Ca-CaCO 3空间框架，以帮助阐明自生添加物在时间尺度上的相对于Ca在海洋中的停留时间（~1 Ma）较短。最终，我们发现，在沉积柱中产生的“自生带”可能会受到碱度过冲或氧化还原状态的影响;在这个区域产生的CaCO 3可以叠加时间信号与深度相关的信号，反映岩性和沉积速率，不需要在空间上是均匀的，即使是由全球事件驱动。最后，我们展示了钙同位素的实用性，探索短时间尺度的气候事件和定量框架，以指导解释。
In this contribution, we explore the idea that the Ca isotope proxy has utility as an indicator of carbonate authigenesis (i.e., post-depositional precipitation of CaCO3within the sedimentary package). Given the strong contrast in isotopic fractionation factor between the formational and diagenetic environments, Ca isotopes have the potential to fingerprint carbonate authigenesis when it occurs close to the seawater-sediment interface. We demonstrate that Ca isotopes are particularly applicable to exploring ocean acidification events, and potentially ocean anoxic events, and focus our attention on ocean acidification related to the Paleocene-Eocene Thermal Maximum (PETM). We present three scenarios that vary in the magnitude and duration of the carbon fluxes that are simulated using an Earth System model of intermediate complexity (cGENIE), and we use the cGENIE output to constrain the upper boundary conditions of 1-D reactive transport models of authigenesis and recrystallization in the sedimentary section. Along with simple mixing calculations, the models inform our exploration of the hypothesis that authigenic carbonate induced by a saturation state overshoot during the PETM explains recently published Ca isotope records, and perhaps bulk carbonate records over Ocean Anoxic Event (OAE) 2. Our simulations suggest that fractionation factor variability does not explain the PETM δ44Ca records, and we propose a δ44Ca-CaCO3space framework to assist with the elucidation of authigenic additions over time scales that are short relative to the residence time of Ca in the ocean (~1 Ma). Ultimately, we find that the ‘authigenic zone’ generated in the sedimentary column may be influenced by alkalinity overshoots or redox state; the CaCO3produced in this zone can overprint temporal signals with depth-dependent signals that reflect lithology and sedimentation rate and need not be spatially uniform, even when driven by a global event. Ultimately, we demonstrate the utility of Ca isotopes for exploring short time scale climatic events and a quantitative framework to guide interpretations.
登录
查看更多内容
DOI：
10.1073/pnas.0802841105
发表时间：
2008-09
期刊：
Proceedings of the National Academy of Sciences
影响因子：
--
作者：
P. Swart
通讯作者：
P. Swart
影响因子：
--
作者：
P. Weller;R. Stein
通讯作者：
P. Weller;R. Stein
影响因子：
5.2
作者：
Adhikari RR;Glombitza C;Nickel JC;Anderson CH;Dunlea AG;Spivack AJ;Murray RW;D'Hondt S;Kallmeyer J
通讯作者：
Kallmeyer J
一些现代碳酸盐沉积物的化学成岩作用
影响因子：
2.9
作者：
R. Berner
通讯作者：
R. Berner
影响因子：
5.3
作者：
F. Richter;Yan Liang
通讯作者：
F. Richter;Yan Liang