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Negative C-isotope excursions at the Permian-Triassic boundary linked to volcanism
http://www.geosociety.org/news/pr/12-63.htm[font face=Serif]…
[font size=5]Negative C-isotope excursions at the Permian-Triassic boundary linked to volcanism[/font]
[font size=4] Jun Shen et al., State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan, Hubei 430074, P.R. China; and Dept. of Geology, University of Cincinnati, Cincinnati, Ohio 45221-0013, USA. Posted online ahead of print 22 Aug. 2012; doi: 10.1130/G33329.1.[/font]
[font size=3]The mass extinction at the Permian-Triassic boundary (PTB), the largest in Earth's history, killed off ~90% of marine species. It is thought to have been caused by the Siberian Traps, a large flood basalt province that erupted ~252 million years ago, but this connection has been inferred on the basis of similarities in age and, thus, is circumstantial. This study by Jun Shen and colleagues documents a strong relationship between marine environmental changes and the deposition of volcanic ash layers in south China, demonstrating for the first time that the PTB biotic crisis was probably triggered by enormous Plinian (explosive) volcanic eruptions. Previous studies of ash layers in south China PTB sections have invoked a source in regional subduction-zone volcanism in the eastern Tethys, but the present study infers an origin as distal deposits of the Siberian Traps. Each ash layer in the Chinese sections shows a negative excursion in the ratio of carbonate or organic carbon isotopes, implying large releases of isotopically light, organic-derived CO[font size=1]2[/font] or methane in conjunction with each eruptive event, consistent with large-scale magma injection into organic-rich sediments of the West Siberian coal province. If confirmed by further investigation, these results will have important implications both for kill mechanisms during the PTB crisis as well as for refinement of the eruption history of the Siberian Traps.
…[/font][/font]
http://dx.doi.org/10.1130/G33329.1
[font size=5]Negative C-isotope excursions at the Permian-Triassic boundary linked to volcanism[/font]
[font size=4] Jun Shen et al., State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan, Hubei 430074, P.R. China; and Dept. of Geology, University of Cincinnati, Cincinnati, Ohio 45221-0013, USA. Posted online ahead of print 22 Aug. 2012; doi: 10.1130/G33329.1.[/font]
[font size=3]The mass extinction at the Permian-Triassic boundary (PTB), the largest in Earth's history, killed off ~90% of marine species. It is thought to have been caused by the Siberian Traps, a large flood basalt province that erupted ~252 million years ago, but this connection has been inferred on the basis of similarities in age and, thus, is circumstantial. This study by Jun Shen and colleagues documents a strong relationship between marine environmental changes and the deposition of volcanic ash layers in south China, demonstrating for the first time that the PTB biotic crisis was probably triggered by enormous Plinian (explosive) volcanic eruptions. Previous studies of ash layers in south China PTB sections have invoked a source in regional subduction-zone volcanism in the eastern Tethys, but the present study infers an origin as distal deposits of the Siberian Traps. Each ash layer in the Chinese sections shows a negative excursion in the ratio of carbonate or organic carbon isotopes, implying large releases of isotopically light, organic-derived CO[font size=1]2[/font] or methane in conjunction with each eruptive event, consistent with large-scale magma injection into organic-rich sediments of the West Siberian coal province. If confirmed by further investigation, these results will have important implications both for kill mechanisms during the PTB crisis as well as for refinement of the eruption history of the Siberian Traps.
…[/font][/font]
