DOI: 10.1111/gbi.12127
Scopus记录号: 2-s2.0-84927007777
论文题名: Hematite-coated microfossils: Primary ecological fingerprint or taphonomic oddity of the Paleoproterozoic?
作者: Shapiro R.S. ; Konhauser K.O.
刊名: Geobiology
ISSN: 1472-4677
EISSN: 1472-4669
出版年: 2015
卷: 13, 期: 3 起始页码: 209
结束页码: 224
语种: 英语
Scopus关键词: burial diagenesis
; discharge
; hematite
; microfossil
; micropaleontology
; paleoecology
; Proterozoic
; taphonomy
; Canada
; Ontario [Canada]
; ferric ion
; ferric oxide
; chemistry
; cyanobacterium
; fossil
; geographic and geological phenomena
; growth, development and aging
; microbiology
; Cyanobacteria
; Ferric Compounds
; Fossils
; Geological Processes
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: Microfossils belonging to the 1.88-billion-year-old 'Gunflint-biota' are preserved as carbonaceous and hematitic filaments and spheres that are believed to represent ancient chemolithoautotrophic Fe(II) oxidizing bacteria that grew above a chemocline where ferruginous seawater upwelled into shallow, oxygenated waters. This 'biological' model posits that hematite formed during burial from dewatering of the precursor ferric oxyhydroxides that encrusted Fe(II)-oxidizing bacteria. Here, we present an alternate 'taphonomic' model in which iron-rich groundwaters discharged into buried stromatolites; thus, the mineralization reactions are more informative of diagenetic processes than they are for primary marine conditions. We sampled centimeter-scale columnar stromatolites from both the lower and upper stromatolite horizons of the Biwabik and Gunflint formations, across a range of metamorphic gradients including unaltered to prehnite-pumpellyite taconite, supergene altered ore, and amphibolite-pyroxene grade contact-metamorphic zones. Fossils are rare to very rare and comprise curved filaments that exist in clusters with similar orientations. The filaments from throughout the Biwabik are similar to well-preserved carbonaceous Gunflintia from Ontario. Spheres of Huroniospora are also found in both formations. Microfossils from the least altered sections are preserved as carbon. Prehnite-pumpellyite samples are composed of either carbon or hematite (Fe2 O3 ). Within the contact aureole, filaments are densely coated by magnetite (Fe3 O4 ); the highest grade samples are secondarily oxidized to martite. The consistency in stromatolite microstructure and lithofacies throughout the metamorphic grades suggests they formed under similar environmental conditions. Post-depositional alteration led to replacement of the carbon by iron oxide. The facies association, filament distribution, and lack of branching and attached spherical cells argue against Gunflintia being a direct analogue to common marine, chemolithoautotrophic Fe(II)-oxidizing bacteria. Instead, we propose that the presence of hematite-coated microfossils is a reflection of taphonomic processes and does not necessarily reflect the byproduct of an original microbial ecosystem. © 2015 John Wiley & Sons Ltd. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/85132
Appears in Collections: 影响、适应和脆弱性
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作者单位: Geological and Environmental Sciences Department, CSU Chico, Chico, CA, United States; Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
Recommended Citation:
Shapiro R.S.,Konhauser K.O.. Hematite-coated microfossils: Primary ecological fingerprint or taphonomic oddity of the Paleoproterozoic?[J]. Geobiology,2015-01-01,13(3)