A 370 million years old mass extinction – different from all others ?

Picture : copyright A.C. Da Silva, Liège

One of Earth’s greatest ecological crises may have had a very different cause than other, better known, extinctions of animal life in Earth’s history, researchers from the Universities of Lausanne and Geneva have found and published in Scientific Reports.

The Devonian mass extinction took place approximately 370 million years ago and was one of the largest in Earth’s history, but the cause of the Devonian extinction remains largely unknown. Meteorite impacts as well as massive volcanism are debated as possible causes. Key to this debate is establishing exactly when the extinction happened, which can then allow the date of the extinction to be compared with the ages of Devonian asteroid impacts and volcanic eruptions. Dr. Joshua Davies and Prof. Urs Schaltegger from the Isotope Geochemistry and Geochronology group at the Department of Earth Sciences of University of Geneva, together with lead author Dr. Lawrence Percival from University of Lausanne, and colleagues from Bremen (D) and Liège (B), pinpointed the date of the extinction to 371.86 million years ago, employing the radioactive decay of uranium into lead in the mineral zircon for the determination of age.

Interestingly though, it does not match the ages of any known Devonian asteroid impact or huge volcanic eruption! Whilst evidence for an asteroid impact or a giant volcanic province may still be waiting to be discovered, it is also possible that neither was linked to the extinction, and that the Devonian event was triggered by processes profoundly different to those that led to later extinctions in Earths’ history like the one causing the end of the dinosaur era at the Cretaceous/Paleogene boundary 66 million years ago. 

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June 26, 2018

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