The end-Permian extinction is resolved to about sixty thousand years

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Burgess, Bowring and Shen published uranium–lead ages on zircons from ash beds through the boundary interval at Meishan, using chemical-abrasion isotope-dilution mass spectrometry to place the Permian–Triassic boundary at 251.902 ± 0.024 million years and to constrain the main marine extinction pulse to roughly sixty thousand years, with an uncertainty of comparable size. The scientific content of this result is not the date but the duration. A biotic collapse spread over millions of years can be explained by ordinary environmental change; one compressed into tens of thousands of years requires a forcing fast enough to outrun the ocean and the carbon cycle, and it is that constraint which makes the Siberian Traps degassing hypothesis compelling rather than merely coincidental.

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