Chuck Bednar for redOrbit.com – @BednarChuck
New evidence of severe losses in brachiopods in the northern Boreal latitudes around the island of Spitsbergen suggest that the controversial Capitanian extinction event that occurred about 262 million years ago should be classified as a true “mass extinction” event.
Previously, the Capitanian extinction event was known only from equatorial settings, and thus its status as a full-fledged global crisis was controversial. However, the researchers that discovered this new evidence suggest that it should be added to the list of the “Big 5” extinctions.
Evidence of severe brachiopod losses discovered
The Capitanian event took place in the Middle Permian but was only recognized 20 years ago, David P.G. Bond from the University of Hull Department of Geography, Environment and Earth Sciences and his colleagues report in the Geological Society of America Bulletin. Previously, the event was only known from equatorial latitudes, casting uncertainty on its global impact.
He and his colleagues look to resolve that by presenting the first proof of severe Middle Permian losses amongst brachiopods in the region of Spitsbergen, the largest and only populated island in the Svalbard archipelago in northern Norway. Their study shows that the this event took place at the same time as an intensification of marine oxygen depletion in the area.
In fact, they write that there were two severe extinctions amongst brachiopods in northern Boreal latitudes during the Middle to Late Permian, separated by a recovery face. The findings are based on new dating of the Spitbergen strata using strontium isotopes, and when compared with well-dated parts of Greenland, they suggest that the first crisis took place in the Capitanian.
“This age assignment indicates that this Middle Permian extinction is manifested at higher latitudes,” Bond and his co-authors wrote. “Redox proxies (pyrite framboids and trace metals) show that the Boreal crisis coincided with an intensification of oxygen depletion, implicating anoxia in the extinction scenario. The widespread and near-total loss of carbonates across the Boreal Realm also suggests a role for acidification in the crisis.”
Should the ‘Big 5’ become the ‘Big 6’ now?
Based on their findings, the researchers believe that the Middle Permian crisis’s status as a true “mass extinction” event has been solidified and that it should be added to the list of the “Big 5” mass extinction events, joining the likes of the well-known Cretaceous-Tertiary extinction event that wiped out the dinosaurs, the ammonites and the last of the pterosaurs.
Other “Big 5” mass extinction events include the Late Devonian mass extinction, which wiped out 75 percent of all species on Earth; the Permian mass extinction, which is also known as The Great Dying because only four percent of species made it through alive; the Ordovician-Silurian mass extinction, which had a drastic impact on marine life forms; and the Triassic-Jurassic mass extinction, which was caused by climate change and an asteroid impact.
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