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  • 1
    Publication Date: 2011-01-07
    Description: Widespread anoxia in the ocean is frequently invoked as a primary driver of mass extinction as well as a long-term inhibitor of evolutionary radiation on early Earth. In recent biogeochemical studies it has been hypothesized that oxygen deficiency was widespread in subsurface water masses of later Cambrian oceans, possibly influencing evolutionary events during this time. Physical evidence of widespread anoxia in Cambrian oceans has remained elusive and thus its potential relationship to the palaeontological record remains largely unexplored. Here we present sulphur isotope records from six globally distributed stratigraphic sections of later Cambrian marine rocks (about 499 million years old). We find a positive sulphur isotope excursion in phase with the Steptoean Positive Carbon Isotope Excursion (SPICE), a large and rapid excursion in the marine carbon isotope record, which is thought to be indicative of a global carbon cycle perturbation. Numerical box modelling of the paired carbon sulphur isotope data indicates that these isotope shifts reflect transient increases in the burial of organic carbon and pyrite sulphur in sediments deposited under large-scale anoxic and sulphidic (euxinic) conditions. Independently, molybdenum abundances in a coeval black shale point convincingly to the transient spread of anoxia. These results identify the SPICE interval as the best characterized ocean anoxic event in the pre-Mesozoic ocean and an extreme example of oxygen deficiency in the later Cambrian ocean. Thus, a redox structure similar to those in Proterozoic oceans may have persisted or returned in the oceans of the early Phanerozoic eon. Indeed, the environmental challenges presented by widespread anoxia may have been a prevalent if not dominant influence on animal evolution in Cambrian oceans.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gill, Benjamin C -- Lyons, Timothy W -- Young, Seth A -- Kump, Lee R -- Knoll, Andrew H -- Saltzman, Matthew R -- England -- Nature. 2011 Jan 6;469(7328):80-3. doi: 10.1038/nature09700.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of California, 900 University Avenue, Riverside, California 92521, USA. bgill@fas.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21209662" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Evolution ; Carbon Cycle ; Carbon Isotopes/analysis ; Carbonates/analysis ; Extinction, Biological ; Fossils ; Geologic Sediments/*chemistry ; History, Ancient ; Iron/analysis/chemistry ; Molybdenum/analysis/chemistry ; Oceans and Seas ; Oxidation-Reduction ; Oxygen/*analysis ; Seawater/*chemistry ; Sulfides/*analysis/chemistry ; Sulfur Isotopes/analysis ; Sweden
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2015-07-24
    Description: Sedimentary rocks deposited across the Proterozoic-Phanerozoic transition record extreme climate fluctuations, a potential rise in atmospheric oxygen or re-organization of the seafloor redox landscape, and the initial diversification of animals. It is widely assumed that the inferred redox change facilitated the observed trends in biodiversity. Establishing this palaeoenvironmental context, however, requires that changes in marine redox structure be tracked by means of geochemical proxies and translated into estimates of atmospheric oxygen. Iron-based proxies are among the most effective tools for tracking the redox chemistry of ancient oceans. These proxies are inherently local, but have global implications when analysed collectively and statistically. Here we analyse about 4,700 iron-speciation measurements from shales 2,300 to 360 million years old. Our statistical analyses suggest that subsurface water masses in mid-Proterozoic oceans were predominantly anoxic and ferruginous (depleted in dissolved oxygen and iron-bearing), but with a tendency towards euxinia (sulfide-bearing) that is not observed in the Neoproterozoic era. Analyses further indicate that early animals did not experience appreciable benthic sulfide stress. Finally, unlike proxies based on redox-sensitive trace-metal abundances, iron geochemical data do not show a statistically significant change in oxygen content through the Ediacaran and Cambrian periods, sharply constraining the magnitude of the end-Proterozoic oxygen increase. Indeed, this re-analysis of trace-metal data is consistent with oxygenation continuing well into the Palaeozoic era. Therefore, if changing redox conditions facilitated animal diversification, it did so through a limited rise in oxygen past critical functional and ecological thresholds, as is seen in modern oxygen minimum zone benthic animal communities.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sperling, Erik A -- Wolock, Charles J -- Morgan, Alex S -- Gill, Benjamin C -- Kunzmann, Marcus -- Halverson, Galen P -- Macdonald, Francis A -- Knoll, Andrew H -- Johnston, David T -- England -- Nature. 2015 Jul 23;523(7561):451-4. doi: 10.1038/nature14589.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA [2] Integrative Oceanography Division, Scripps Institution of Oceanography, La Jolla, California 90089, USA. ; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA. ; Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA. ; Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA. ; Department of Earth and Planetary Sciences/GEOTOP, McGill University, Montreal, Quebec, H3A 0E8, Canada. ; 1] Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA [2] Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26201598" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atmosphere/chemistry ; Biodiversity ; Geologic Sediments/chemistry ; History, Ancient ; Iron/*analysis/*chemistry ; Oceans and Seas ; Oxidation-Reduction ; Oxygen/*analysis/*chemistry/metabolism ; Seawater/chemistry ; Sulfides/metabolism ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2018-05-16
    Description: Mass extinctions documented by the fossil record provide critical benchmarks for assessing changes through time in biodiversity and ecology. Efforts to compare biotic crises of the past and present, however, encounter difficulty because taxonomic and ecological changes are decoupled, and although various metrics exist for describing taxonomic turnover, no methods...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2014-01-25
    Description: Opportunity has investigated in detail rocks on the rim of the Noachian age Endeavour crater, where orbital spectral reflectance signatures indicate the presence of Fe(+3)-rich smectites. The signatures are associated with fine-grained, layered rocks containing spherules of diagenetic or impact origin. The layered rocks are overlain by breccias, and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the Endeavour impact. Compositional data for fractures in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Evidence is thus preserved for water-rock interactions before and after the impact, with aqueous environments of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate-rich rocks at Meridiani Planum.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arvidson, R E -- Squyres, S W -- Bell, J F 3rd -- Catalano, J G -- Clark, B C -- Crumpler, L S -- de Souza, P A Jr -- Fairen, A G -- Farrand, W H -- Fox, V K -- Gellert, R -- Ghosh, A -- Golombek, M P -- Grotzinger, J P -- Guinness, E A -- Herkenhoff, K E -- Jolliff, B L -- Knoll, A H -- Li, R -- McLennan, S M -- Ming, D W -- Mittlefehldt, D W -- Moore, J M -- Morris, R V -- Murchie, S L -- Parker, T J -- Paulsen, G -- Rice, J W -- Ruff, S W -- Smith, M D -- Wolff, M J -- New York, N.Y. -- Science. 2014 Jan 24;343(6169):1248097. doi: 10.1126/science.1248097.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, Washington University in Saint Louis, St. Louis, MO 63130, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24458648" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteria ; *Exobiology ; Extraterrestrial Environment/*chemistry ; Geologic Sediments ; Hydrogen-Ion Concentration ; *Mars ; Silicates/analysis/chemistry ; Spacecraft ; Sulfates/chemistry ; *Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2012-03-10
    Description: On the basis of putative nuclei and endospores, Huldtgren et al. (Reports, 23 December 2011, p. 1696) propose that embryo-like Doushantuo microfossils are nonmetazoan holozoans akin to mesomycetozoeans. However, both size and preservation preclude interpretation of internal structures as nuclei. Moreover, the authors may have conflated two different populations; some specimens display a pseudoparenchymatous organization incompatible with a mesomycetozoean comparison.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Xiao, Shuhai -- Knoll, Andrew H -- Schiffbauer, James D -- Zhou, Chuanming -- Yuan, Xunlai -- New York, N.Y. -- Science. 2012 Mar 9;335(6073):1169; author reply 1169. doi: 10.1126/science.1218814.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. xiao@vt.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22403373" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Nucleus/*ultrastructure ; Eukaryota/*growth & development ; *Fossils
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2012-05-05
    Description: The rover Opportunity has investigated the rim of Endeavour Crater, a large ancient impact crater on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized craters on Earth. Highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks adjacent to the crater rim. The gypsum was precipitated from low-temperature aqueous fluids flowing upward from the ancient materials of the rim, leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate-rich sandstones of the Meridiani region.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Squyres, S W -- Arvidson, R E -- Bell, J F 3rd -- Calef, F 3rd -- Clark, B C -- Cohen, B A -- Crumpler, L A -- de Souza, P A Jr -- Farrand, W H -- Gellert, R -- Grant, J -- Herkenhoff, K E -- Hurowitz, J A -- Johnson, J R -- Jolliff, B L -- Knoll, A H -- Li, R -- McLennan, S M -- Ming, D W -- Mittlefehldt, D W -- Parker, T J -- Paulsen, G -- Rice, M S -- Ruff, S W -- Schroder, C -- Yen, A S -- Zacny, K -- New York, N.Y. -- Science. 2012 May 4;336(6081):570-6. doi: 10.1126/science.1220476.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Cornell University, Ithaca, NY 14853, USA. squyres@astro.cornell.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22556248" target="_blank"〉PubMed〈/a〉
    Keywords: Calcium Sulfate ; Extraterrestrial Environment ; Geological Phenomena ; *Mars ; Meteoroids ; Silicates ; Spacecraft ; *Water ; Zinc
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 50 (1963), S. 546-546 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 44 (1957), S. 394-394 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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