Calibrating the triple oxygen isotope composition of evaporite minerals as a proxy for marine sulfate
Calibrating the triple oxygen isotope composition of evaporite minerals as a proxy for marine sulfate
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DOI：
10.1016/j.epsl.2021.117320
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发表时间：
2022-01
影响因子：
5.3
通讯作者：
A. Waldeck;Haley C. Olson;W. Yao;C. Blättler;A. Paytan;D. Hodell;D. Johnston
中科院分区：
文献类型：
--
作者：
A. Waldeck;Haley C. Olson;W. Yao;C. Blättler;A. Paytan;D. Hodell;D. Johnston
海水硫酸盐的三重氧同位素组成记录在海洋硫酸盐碳酸盐岩和重晶石中，常用于解释过去大气pO 2/pCO 2和总初级生产力（GPP）的变化。在实践中，从海洋蒸发存款硫酸盐的最负的三重氧同位素值（17 O）的测量被认为是最接近代表同期海水硫酸盐，并用于计算大气成分。然而，一系列的三重氧同位素组成通常是在一个单一的海洋蒸发岩盆地内测量。在这里，我们详细描述了三重氧同位素组成的硫酸盐石膏样品从三个墨西拿（5-6马）海洋蒸发岩子盆地从西地中海盆地的变化。蒸发岩硫酸盐是从同期海水硫酸盐抵消，并反映了两个端员硫酸盐人口之间的混合：原始海水硫酸盐和硫酸盐，已被同位素重置盆地限制后。在地层环境中，硫酸盐的δ 17 O和δ 18 O组合提供了一个机会，以更好地限制海洋硫酸盐碳酸盐岩保存开阔海洋海水硫酸盐的原始同位素组成的程度。这项研究包括探索质量相关的分馏，同位素平衡与水，和各种方案的混合。我们的研究结果校准海洋硫酸盐方解石在约束同期，开放的海洋三重氧同位素组成的海水硫酸盐的效用。
The triple oxygen isotope composition of seawater sulfate, as recorded in marine sulfate evaporites and barites, is commonly used to interpret past changes in atmospheric pO 2/pCO 2 and gross primary production (GPP). In practice, the most-negative measured triple oxygen isotope value (Δ'17 O) of sulfate from a marine evaporite deposit is thought to most closely represent contemporaneous seawater sulfate and is used to calculate atmospheric composition. However, a range of triple oxygen isotope compositions are typically measured within a single marine evaporite basin. Here, we characterize in detail the variability in the triple oxygen isotope composition of the sulfate in gypsum sampled from three Messinian (5-6 Ma) marine evaporite sub-basins from the Western Mediterranean Basin. Evaporite sulfate is offset from contemporaneous seawater sulfate and reflects mixing between two end-member sulfate populations: the original seawater sulfate and sulfate that has been isotopically reset after basin restriction. The combined Δ'17 O and δ 18 O compositions of sulfate within a stratigraphic context offer the opportunity to better constrain the degree to which marine sulfate evaporites preserve the original isotopic composition of open ocean seawater sulfate. This study encompasses an exploration of mass-dependent fractionation, isotope equilibrium with water, and various scenarios of mixing. Our results calibrate the utility of marine sulfate evaporites in constraining the contemporaneous, open ocean triple oxygen isotope composition of seawater sulfate.