UAE rocks tell story of mass extinction

The riddle of a mass extinction a quarter of a billion years ago has been solved by scientists.

Chemical analysis of UAE rocks have shown a rapid increase in acidity of the world’s oceans contributed to mass extinction. Jorge Silva / Reuters

Rocks from the UAE have helped to solve the riddle of what caused the extinction of 90 per cent of marine species and two thirds of land animals 252 million years ago.

And the stones also offer a cautionary tale about today’s environmental changes. Scientists have used chemical analysis of the rocks to discover that a rapid increase in the acidity of the world’s oceans, caused by volcanic activity, contributed to the mass extinction.

Published in the journal Science, the work found the type of boron found in UAE rocks had changed, indicating that the oceans had become more acidic. The rocks were in what was a shallow sea at the time.

Before this, many organisms had been wiped out by changes in oxygen levels in the atmosphere, and the rocks indicate the rate of extinction was intensified by chemical upheavals in the sea.

That second bout of destruction particularly targeted marine organisms with calcified shells.

The destruction was known as the Permian-Triassic boundary mass extinction because it happened between the Permian and Triassic geological periods.

Prof Tim Lenton, from the University of Exeter, helped to design a theoretical model that explained the data from the rocks.

“For the first time it’s providing some smoking-gun evidence for this largest mass extinction in the record,” Prof Lenton said. “It’s shedding new light on a very familiar problem.”

It is thought that large amounts of lava from the Earth’s mantle was coming out of what is now Siberia and heating up sedimentary carbonate rocks from the Earth’s crust.

This caused vast amounts of carbon dioxide to be released into the atmosphere, which caused the lethal acidification of the world’s oceans.

“You have this mantle magma, if you like, just splurging out but extending sideways and cooking an awful lot of carbonate rocks,” said Prof Lenton, who specialises in climate change and Earth systems science.

Describing the data from the rocks as “beautiful in their complexity”, he and a colleague at Exeter, Dr Stuart Daines, spent the equivalent of about three months analysing the information from the rocks to come up with a model that explained what happened.

Much of the fieldwork in the UAE was carried out by researchers from the University of Edinburgh.

During the first phase of the Permian-Triassic boundary extinction there was a “slow” injection of carbon into the Earth’s atmosphere, the researchers say, although this is not thought to have had much effect on the acidity of the oceans.

It was only during the second phase of the extinction that the seas became much more acidic.

As the modern-day release of carbon dioxide by human activities is also causing the oceans to acidify, the recent study offers a stark warning of the damage marine ecosystems could suffer if this process continues.

The University of Edinburgh says the amount of carbon volcanic activity added to the atmosphere 252 million years ago was “probably greater than today’s fossil-fuel reserves”.

But the rate of release, which “was a critical factor driving ocean acidification”, is being matched by what is taking place today.

Other researchers involved in the study were based at other UK universities, and some in Austria and Germany.

The Permian-Triassic extinction is the largest ever such event and one of five commonly recognised.

Other mass extinctions include the Cretaceous-Paleogene extinction 66 million years ago, which wiped out all remaining non-flying dinosaurs.