Geology

Volcanic Vetting

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Science  19 Dec 2008:
Vol. 322, Issue 5909, pp. 1759
DOI: 10.1126/science.322.5909.1759c

Two major extinctions, at the end of the Permian and end of the Cretaceous, appear to have been coincident with massive volcanic eruptions, of the Siberian and Deccan flood basalts respectively. Two studies provide tighter constraints on these associations, the duration of these events, and their potential climatic consequences. Reichow et al. provide new Ar-Ar dates on the main eruption of the Siberian flood basalts. The data imply that the eruptions occurred in less than 2 million years, and perhaps a few hundred thousand years, beginning shortly before the extinction (about 250 million years ago) and extending into it. Chenet et al. analyzed paleomagnetic data through individual flows in the upper part of the thick Deccan sequence. Their data show that many separate flows have the same paleomagnetic direction, implying that they erupted together in a time shorter than the inferred drift of the orientation of Earth's magnetic field. Four thick packages of flows may have each erupted in as little as a few decades, and the 1200-m section sampled, containing some soil layers, may have formed in less than 100,000 years. Such rates would have emitted copious amounts of sulfur dioxide. — BH

Earth Planet. Sci. Lett. 10.1016/j.epsl.2008.09.030 (2008); J. Geophys. Res. 113, B04101 (2008).

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