No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction
Sofie Lindstrm et al., GEUS (Geological Survey of Denmark and Greenland), ster Voldgade 10, DK-1350 Copenhagen K, Denmark. Posted online ahead of print 10 April 2012; doi: 10.1130/G32928.1.
The end-Triassic mass extinction event (201 million years ago) severely affected animals and plants both in the sea and on land. Carbon isotope records across the Triassic-Jurassic (T/J) boundary show at least two prominent negative peaks interpreted to reflect injection of light carbon to the atmosphere, either from massive volcanic emissions of carbon dioxide or from release of methane through contact metamorphism during the initial stages of the breakup of the supercontinent Pangea. In particular, the most prominent negative carbon isotope peak has been suggested as the trigger of the end-Triassic event. Sofie Lindstrm and colleagues present a new, extended organic carbon isotope record across the T/J boundary in the Danish Basin, which correlates with reference records from the UK, providing new evidence that the major biotic changes, both on land and in the oceans, commenced prior to the most prominent negative carbon isotope excursion. If massive methane release was involved, it did not trigger the end-Triassic mass extinction, at least not on land. Instead, the highest negative C-isotope excursion is contemporaneous with the onset of floral recovery on land, whereas marine ecosystems remained disturbed for millions of years after the event.
Hf-Nd isotope variation in Mariana Trough basalts: The importance o
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Geological Society of America