DOI: 10.1111/gbi.12262
Scopus记录号: 2-s2.0-85032916968
论文题名: The late-stage “ferruginization” of the Ediacara Member (Rawnsley Quartzite, South Australia): Insights from uranium isotopes
作者: Tarhan L.G. ; Planavsky N.J. ; Wang X. ; Bellefroid E.J. ; Droser M.L. ; Gehling J.G.
刊名: Geobiology
ISSN: 1472-4677
EISSN: 1472-4669
出版年: 2018
卷: 16, 期: 1 起始页码: 35
结束页码: 48
语种: 英语
英文关键词: Australia
; Ediacara Biota
; Ediacaran Period
; iron oxides
; paleoenvironment
Scopus关键词: assessment method
; biota
; Ediacaran
; fossilization
; groundwater
; iron oxide
; marine environment
; paleoenvironment
; paleosol
; reconstruction
; sandstone
; sedimentology
; taphonomy
; terrestrial environment
; uranium
; uranium isotope
; Australia
; South Australia
Scopus学科分类: Earth and Planetary Sciences: General Earth and Planetary Sciences
; Environmental Science: General Environmental Science
; Agricultural and Biological Sciences: Ecology, Evolution, Behavior and Systematic
英文摘要: The paleoenvironmental setting in which the Ediacara Biota lived, died, and was preserved in the eponymous Ediacara Member of the Rawnsley Quartzite of South Australia is an issue of long-standing interest and recent debate. Over the past few decades, interpretations have ranged from deep marine to shallow marine to terrestrial. One of the key features invoked by adherents of the terrestrial paleoenvironment hypothesis is the presence of iron oxide coatings, inferred to represent the upper horizons of paleosols, along fossiliferous sandstone beds of the Ediacara Member. We find that these surficial oxides are characterized by (234U/238U) values which are not in secular equilibrium, indicating extensive fluid-rich alteration of these surfaces within the past approximately 2 million years. Specifically, the oxide coatings are characterized by (234U/238U) values >1, indicating interaction with high-(234U/238U) fluids derived from alpha-recoil discharge. These oxides are also characterized by light “stable” δ238/235U values, consistent with a groundwater U source. These U isotope data thus corroborate sedimentological observations that ferric oxides along fossiliferous surfaces of the Ediacara Member consist of surficial, non-bedform-parallel staining, and sharply irregular patches, strongly reflecting post-depositional, late-stage processes. Therefore, both sedimentological and geochemical evidence indicate that Ediacara iron oxides do not reflect synsedimentary ferruginization and that the presence of iron oxides cannot be used to either invoke a terrestrial paleoenvironmental setting for or reconstruct the taphonomic pathways responsible for preservation of the Ediacara Biota. These findings demonstrate that careful assessment of paleoenvironmental parameters is essential to the reconstruction of the habitat of the Ediacara Biota and the factors that led to the fossilization of these early complex ecosystems. © 2017 John Wiley & Sons Ltd Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/85026
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作者单位: Department of Geology and Geophysics, Yale University, New Haven, CT, United States; Department of Earth Sciences, University of California, Riverside, Riverside, CA, United States; South Australian Museum and University of Adelaide, Adelaide, SA, Australia
Recommended Citation:
Tarhan L.G.,Planavsky N.J.,Wang X.,et al. The late-stage “ferruginization” of the Ediacara Member (Rawnsley Quartzite, South Australia): Insights from uranium isotopes[J]. Geobiology,2018-01-01,16(1)