气候变化领域集成服务门户(CCPortal): Uranium isotopes as a proxy for primary depositional redox conditions in organic-rich marine systems

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DOI	10.1016/j.epsl.2019.115878
	Uranium isotopes as a proxy for primary depositional redox conditions in organic-rich marine systems
	Abshire M.L.; Romaniello S.J.; Kuzminov A.M.; Cofrancesco J.; Severmann S.; Riedinger N.
发表日期	2020
ISSN	0012821X
卷号	529
英文摘要	In marine sediments, authigenic uranium (U) enrichments and U isotope compositions are important tools for interpreting changes in redox conditions, however, their use as paleoproxies requires a comprehensive understanding of the dominant processes that contribute to sediments becoming enriched or depleted. This study focuses on the U content and 238U/235U ratio of organic-rich surface sediments from the Namibian continental margin, where high productivity results in an expanded oxygen minimum zone (OMZ). The investigated core sample sites are located on the shelf, shelf break, and slope where bottom water redox conditions vary from anoxic to suboxic to oxic, respectively. While all cores have relatively high total organic carbon (TOC) contents (up to 12 wt.%), each location displays a unique U to TOC relationship. Shelf sediment exhibit a fair correlation between U and TOC, while the shelf break and slope sediments show a pronounced decoupling of U and TOC. On the Namibia continental margin, particle-rich nepheloid layers transport organic-rich deposits from within the OMZ, through oxic water, to be redeposited on the slope. Due to the sensitivity of U to changes in redox conditions, this lateral movement results in the release of the reduced U phases back into the water column through oxidation while transporting the partially remineralized organic carbon to the slope. Oxidation of U during transport does not alter the average primary 238U/235U isotopic signature in redeposited sediment, and the combination of high TOC, low U content and high δ238U values may become a useful tool for the identification of the boundaries of ancient OMZs. © 2019 Elsevier B.V.
关键词	paleoceanography redeposition redox upwelling uranium uranium isotopes
英文关键词	Isotopes; Nuclear fuels; Sediments; Submarine geology; Uranium; Paleoceanography; Redeposition; redox; upwelling; Uranium isotopes; Organic carbon; enrichment; isotopic composition; marine sediment; paleoceanography; redeposition; redox conditions; sediment chemistry; upwelling; uranium isotope; Atlantic Ocean; Namibian Margin
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/202464
作者单位	Boone Pickens School of Geology, Oklahoma State University, Stillwater, OK 74078, United States; Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, United States; Department of Marine and Coastal Sciences, Rutgers, State University, New Brunswick, NJ 08901, United States
推荐引用方式 GB/T 7714	Abshire M.L.,Romaniello S.J.,Kuzminov A.M.,et al. Uranium isotopes as a proxy for primary depositional redox conditions in organic-rich marine systems[J],2020,529.
APA	Abshire M.L.,Romaniello S.J.,Kuzminov A.M.,Cofrancesco J.,Severmann S.,&Riedinger N..(2020).Uranium isotopes as a proxy for primary depositional redox conditions in organic-rich marine systems.Earth and Planetary Science Letters,529.
MLA	Abshire M.L.,et al."Uranium isotopes as a proxy for primary depositional redox conditions in organic-rich marine systems".Earth and Planetary Science Letters 529(2020).