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Ireviken event

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Ireviken event

The Ireviken event was a minor extinction event at the Llandovery/Wenlock boundary (mid Silurian, ). The event is best recorded at Ireviken, Gotland, where over 50% of trilobite species went extinct; 80% of the global conodont species also become extinct in this interval.

Anatomy of the event

The event lasted around 200,000 years, spanning the base of the Wenlock epoch.[2][3]

It comprises eight extinction "datum points"—the first four being regularly spaced, every 30,797 years, and linked to the Milankovic obliquity cycle.[3] The fifth and sixth probably reflect maxima in the precessional cycles, with periods of around 16.5 and 19 ka.[3] The final two data are much further spaced, so harder to link with Milankovic changes.[3]

Casualties

The mechanism responsible for the event originated in the deep oceans, and made its way into the shallower shelf seas. Correspondingly, shallow-water reefs were barely affected, while pelagic and hemipelagic organisms such as the graptolites, conodonts and trilobites were hit hardest.[2]

Geochemistry

Subsequent to the first extinctions, excursions in the δ13C and δ18O records are observed; δ13C rises from +1.4‰ to +4.5‰, while δ18O increases from −5.6‰ to −5.0‰.[2]

See also

Anoxic event

References

  1. ^
  2. ^ a b c d
  3. ^ a b c d
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