DOI: 10.1016/j.epsl.2018.09.020
Scopus记录号: 2-s2.0-85054073231
论文题名: Global seawater redox trends during the Late Devonian mass extinction detected using U isotopes of marine limestones
作者: White D.A. ; Elrick M. ; Romaniello S. ; Zhang F.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 503 起始页码: 68
结束页码: 77
语种: 英语
英文关键词: anoxia
; epeiric seas
; extinction
; Late Devonian seawater redox
; redox-sensitive metals
; uranium isotopes
Scopus关键词: Deposits
; Isotopes
; Light extinction
; Lime
; Limestone
; Nuclear fuels
; Seawater
; Tropics
; anoxia
; epeiric seas
; Late Devonian
; Redox-sensitive metals
; Uranium isotopes
; Anoxic sediments
英文摘要: The Late Devonian extinction ranks as one of the ‘big five’ Phanerozoic extinctions affecting up to 80% of marine species and is characterized by two major extinction events that are separated by <3 My. The leading hypotheses explaining both extinction events are global cooling and/or widespread marine anoxia. We test the marine anoxia hypothesis by analyzing uranium isotopes (δ238U) across a ∼7 My interval of well-dated Upper Devonian marine limestones from the Devil's Gate Formation in Nevada, USA. The measured δ238U curve shows no co-variation with local sediment-derived redox trends, water-depth dependent facies changes, redox-sensitive metals, TOC, or diagnostic elemental ratios. From these relationships, we infer that the δ238U curve represents global seawater redox conditions. Two negative δ238U excursions (indicating more reducing seawater) are observed with durations of ∼3.8 My (late Frasnian) and ∼1.1 My (early Famennian), respectively. Steady-state modeling of the observed −0.2 to −0.3‰ shifts in δ238U points to a ∼5–15% increase in the total area of anoxic seafloor during these excursions. The late Frasnian negative excursion is broadly coincident with the first extinction event (late rhenana Zone or lower Kellwasser event), whereas the early Famennian negative excursion (lower-middle triangularis zones) occurs after the most intense Frasnian–Famennian boundary (F–F) extinction event (upper Kellwasser event). Compilations of local sediment redox conditions from Upper Devonian marine deposits with conodont zone-level age control indicates that the extinction events were coincident with widespread anoxic deposits accumulating in subtropical epeiric sea and some open ocean settings, supporting previous interpretations that widespread marine anoxia had an important influence on the Late Devonian extinctions. The temporal relationships between global-ocean redox trends represented by the δ238U curve and the newly compiled subtropical marine redox sediment trends indicates that local epeiric seawaters carried a similar U-isotopic composition as the open ocean for the majority of the studied interval except for a brief interval (<500 ky) spanning the F–F boundary. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109620
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States; School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, United States
Recommended Citation:
White D.A.,Elrick M.,Romaniello S.,et al. Global seawater redox trends during the Late Devonian mass extinction detected using U isotopes of marine limestones[J]. Earth and Planetary Science Letters,2018-01-01,503