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Science 15 May 1998:
Vol. 280. no. 5366, p. 1007
DOI: 10.1126/science.280.5366.1007
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Research News

PALEONTOLOGY:
Biggest Extinction Looks Catastrophic

Richard A. Kerr

Most paleontologists have believed that the mass extinction at the end of the Permian period 250 million years ago was long and slow and had causes such as gradual sea level fall and climate change. But last year new dates from Chinese rocks shrank the final pulse of marine extinctions to less than 1 million years. Now more dating of the same rocks squeezes the disaster even further--and suggests a catastrophic cause, perhaps even a comet or asteroid impact. The new results, reported on page 1039, show that a shift in the ratio of carbon isotopes recorded in marine rocks--an event intimately tied to the extinctions--lasted perhaps as little as 10,000 years.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)