气候变化领域集成服务门户(CCPortal): Brachiopod δ34SCAS microanalyses indicate a dynamic, climate-influenced Permo-Carboniferous sulfur cycle

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DOI	10.1016/j.epsl.2020.116428
	Brachiopod δ34SCAS microanalyses indicate a dynamic, climate-influenced Permo-Carboniferous sulfur cycle
	Johnson D.L.; Grossman E.L.; Webb S.M.; Adkins J.F.
发表日期	2020
ISSN	0012821X
卷号	546
英文摘要	Early isotopic studies of sulfate in carbonate minerals (carbonate associated sulfate; CAS) suggested that carbonates can provide a reliable, well-dated archive of the marine sulfur cycle through time. However, subsequent research has shown that diagenetic alteration can impose highly heterogeneous CAS sulfur isotopic compositions (δ34SCAS) among different carbonate phases within sediments. Such alteration necessitates targeted sampling of well-preserved, primary carbonate phases. Here, we present a new record of Carboniferous and Early Permian brachiopod δ34SCAS generated from over 130 measurements of microsampled brachiopod shells. Our record refines existing brachiopod δ34SCAS records and confirms a large, ∼6.5‰ δ34SCAS decrease in the Early Carboniferous. Importantly, the record also features a novel 3–5‰ increase in δ34SCAS near the Serpukhovian-Bashkirian boundary (323.4 Ma) that coincides with carbonate δ13C and δ18O increases. Variability in δ34SCAS is minor both within (≤0.3‰) and among (≤2‰) individual co-depositional brachiopod specimens. A taxon-specific δ34SCAS offset is present one species (Composita subtilita) that also exhibits a δ13C offset, supporting the existence of biological “vital effects” on δ34SCAS. Geologic evidence and mathematical modeling of the Permo-Carboniferous carbon and sulfur cycles suggest that changes in the burial ratio of organic carbon to pyrite sulfur (RC:S) are insufficient to explain the observed mid-Carboniferous δ34SCAS record. We find that changes in the 34S depletion of pyrite relative to seawater sulfate (ε34) or in the δ34S of the input to the ocean (δ34Sin) are also needed. Large additions of O2 from organic carbon burial during the Permo-Carboniferous cannot be entirely compensated for with sulfur cycle changes; lower than modern late Visean pO2 and/or additional O2 sinks are needed to keep pO2 at plausible levels. Based on the geologic context surrounding our record's mid-Carboniferous δ34SCAS increase, we advocate for simultaneous changes in pyrite burial, ε34, and δ34Sin, driven by sea level or tectonically induced changes in environments of sulfur burial, as a viable mechanism to produce rapid seawater δ34S changes. © 2020 Elsevier B.V.
关键词	biogeochemical cycles brachiopods carbonate associated sulfate Permo-Carboniferous sulfur isotope geochemistry
英文关键词	Carbonation; Isotopes; Organic carbon; Pyrites; Sea level; Seawater; Sulfate minerals; Carbonate-associated sulfates; Diagenetic alteration; Isotopic composition; Isotopic study; Measurements of; Organic carbon burial; Sulfur cycles; Vital effects; Sulfur; biostratigraphy; brachiopod; carbonate; Carboniferous; fossil assemblage; fossil record; paleoenvironment; Permian; sulfur cycle; Brachiopoda
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202683
推荐引用方式 GB/T 7714	Johnson D.L.,Grossman E.L.,Webb S.M.,et al. Brachiopod δ34SCAS microanalyses indicate a dynamic, climate-influenced Permo-Carboniferous sulfur cycle[J],2020,546.
APA	Johnson D.L.,Grossman E.L.,Webb S.M.,&Adkins J.F..(2020).Brachiopod δ34SCAS microanalyses indicate a dynamic, climate-influenced Permo-Carboniferous sulfur cycle.Earth and Planetary Science Letters,546.
MLA	Johnson D.L.,et al."Brachiopod δ34SCAS microanalyses indicate a dynamic, climate-influenced Permo-Carboniferous sulfur cycle".Earth and Planetary Science Letters 546(2020).