Sulfur-isotope evidence for recovery of seawater sulfate concentrations from a PTB minimum by the Smithian-Spathian transition
Sulfur-isotope evidence for recovery of seawater sulfate concentrations from a PTB minimum by the Smithian-Spathian transition
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DOI：
10.1016/j.earscirev.2018.08.010
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发表时间：
2019-08
影响因子：
12.1
通讯作者：
A. Stebbins;T. Algeo;T. Algeo;C. Olsen;H. Sano;H. Rowe;R. Hannigan
中科院分区：
文献类型：
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作者：
A. Stebbins;T. Algeo;T. Algeo;C. Olsen;H. Sano;H. Rowe;R. Hannigan
早三叠世的Smithian-Spathian亚阶段界线（SSB）是二叠纪末生物大灭绝事件后海洋动物群和生态系统长期恢复过程中的一个重要时段。虽然一些特提斯SSB部分已被研究，很少有信息是关于在泛海底的环境条件，其中包括约85%的早三叠世全球海洋，在Smithian-Spathian过渡。了解早三叠世碳、硫循环的变化，对于阐明海洋油气恢复的模式和控制因素具有重要意义。特别是我们对早三叠世硫循环的理解是不完整的。在这项研究中，我们报告碳酸盐碳和氧，碳酸盐相关的硫酸盐（CAS）硫和氧，黄铁矿硫同位素比从Jesmond节，卡奇克里克地，加拿大西部。这一部分，作为一个热带碳酸盐环礁形成于泛大洋中部，跨越了最新的史密斯到中斯帕提斯。δ 34 SCA和δ 18 OCAS都在SSB转变期间增加，然后在早期斯帕斯期减少，与δ 13 Ccarb剖面的变化相匹配。我们推测，在SSB的δ 34 SCA和δ 18 OCAS的急剧增加反映了微生物硫酸盐还原（MSR）和黄铁矿埋藏量的全球增加。推动这一增加MSR和黄铁矿埋藏冷却温度，提高初级生产力，并增加有机质的可用性。SSB之后的下降趋势表明，这些环境变化达到了最大值，并开始减少或扭转在早期Spathian。δ 34 SCAS-pyr值与δ 34 Spyr值之间的差值（Δ 34 SCAS-pyr）从最晚的Smithian到Spathian中期保持相对稳定。这种稳定性提供了一个估计MSR硫同位素枯竭，使我们能够估计古海水硫酸盐浓度。使用“MSR-trend”方法，我们估计早三叠世海水硫酸盐浓度在2.5和9.1 mM之间。这些估计值高于先前公布的二叠纪-三叠纪界线的值，表明早三叠世晚期海水硫酸盐的总体增加。
The Smithian-Spathian substage boundary (SSB) in the Early Triassic was an important time interval during the protracted recovery of marine faunas and ecosystems following the end-Permian mass extinction event. Although some Tethyan SSB sections have been studied, little information is available regarding environmental conditions in the Panthalassic Ocean, which comprised ~85% of the Early Triassic global ocean, during the Smithian-Spathian transition. Understanding changes in the carbon and sulfur cycles during the Early Triassic is important for deciphering the pattern and controls on the marine recovery. Our understanding of the Early Triassic sulfur cycle, in particular, is incomplete. In this study, we report carbonate carbon and oxygen, carbonate-associated sulfate (CAS) sulfur and oxygen, and pyritic sulfur isotopic ratios from the Jesmond section, Cache Creek Terrane, western Canada. This section, which formed as a tropical carbonate atoll in the middle of the Panthalassic Ocean, spans the latest Smithian to middle Spathian. Both δ34SCASand δ18OCASincreased through the SSB transition before decreasing in the early Spathian, matching variation in the δ13Ccarbprofile. We hypothesize that the sharp increase in δ34SCASand δ18OCASat the SSB reflects a global increase in the amount of microbial sulfate reduction (MSR) and pyrite burial. Driving this increase in MSR and pyrite burial were cooling temperatures, increasing primary productivity, and increasing organic matter availability. The decreasing trend immediately following the SSB indicates that these environmental changes reached maxima and began to diminish or reverse in the early Spathian. The difference between δ34SCASand δ34Spyrvalues (Δ34SCAS-pyr) remained relatively stable from the latest Smithian through the middle Spathian. This stability provides an estimate of MSR sulfur-isotope depletion allowing us to estimate paleo-seawater sulfate concentrations. Using the “MSR-trend” method, we estimate that Early Triassic seawater sulfate concentrations were between 2.5 and 9.1 mM. These estimates are higher than previously published values for the Permian-Triassic boundary, suggesting an overall increase in seawater sulfate by the late Early Triassic.