气候变化领域集成服务门户(CCPortal): The role of authigenic carbonate in Neoproterozoic carbon isotope excursions

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DOI	10.1016/j.epsl.2020.116534
	The role of authigenic carbonate in Neoproterozoic carbon isotope excursions
	Laakso T.A.; Schrag D.P.
发表日期	2020
ISSN	0012821X
卷号	549
英文摘要	Sedimentary carbonates from the Neoproterozoic Era host some of the largest carbon isotope excursions in the geological record, in some cases as large as 12‰ to 15‰. The origin of these signals remains a matter of debate – including whether they reflect local diagenetic effects, or record changes in the dissolved inorganic carbon (DIC) of global seawater that are indicative of shifts in the larger carbon cycle. Producing such changes through oxidation of organic carbon or methane requires unreasonably large fluxes that imply massive perturbations to carbon and oxygen budgets that are not observed. We present a plausible way to drive large changes in the δ13C of the global ocean via large-scale precipitation of isotopically fractionated authigenic carbonates distributed globally at modest concentrations in terrigenous sediments, particularly if the isotopic fractionation of authigenic carbonate shifts rapidly relative to average marine carbonate. We suggest that changes in the fractionation associated with authigenic carbonate precipitation could therefore be responsible for at least some of the variability in isotopic records drawn from primary marine carbonate. Using a diffusion-reaction model, we find that oscillations in sulfate concentrations are one mechanism for altering the isotopic composition of authigenic carbonates, thus forcing abrupt changes in seawater δ13C. This mechanism is particularly effective under the geochemical conditions that likely prevailed during the Neoproterozoic. A sulfate-driven, authigenic origin for Neoproterozoic carbon isotope excursions makes testable predictions for the expression of the anomaly over depth transects, and for the evolution of δ34S through such events. © 2020 Elsevier B.V.
关键词	authigenic carbonate carbon isotopes Neoproterozoic
英文关键词	Budget control; Carbonates; Carbonation; Isotopes; Seawater effects; Sulfur compounds; Authigenic carbonates; Carbon isotope excursions; Diffusion-reaction model; Dissolved inorganic carbon; Geochemical conditions; Isotopic fractionations; Large-scale precipitation; Sulfate concentrations; Organic carbon; authigenic mineral; carbon isotope; carbonate rock; concentration (composition); dissolved inorganic carbon; isotopic composition; isotopic fractionation; Proterozoic; sedimentary rock
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/202711
作者单位	Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02139, United States
推荐引用方式 GB/T 7714	Laakso T.A.,Schrag D.P.. The role of authigenic carbonate in Neoproterozoic carbon isotope excursions[J],2020,549.
APA	Laakso T.A.,&Schrag D.P..(2020).The role of authigenic carbonate in Neoproterozoic carbon isotope excursions.Earth and Planetary Science Letters,549.
MLA	Laakso T.A.,et al."The role of authigenic carbonate in Neoproterozoic carbon isotope excursions".Earth and Planetary Science Letters 549(2020).