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Clue in 250m-year-old extinction mystery

NZ NewswireNZ Newswire 19/07/2016

The researchers said they hoped the study would help scientists better understand the consequences of environmental change. © Getty Images The researchers said they hoped the study would help scientists better understand the consequences of environmental change. It took millions of years for life on earth to recover from what is described as the greatest mass extinction of all time - now scientists say they've found a clue to help explain why.

About 90 per cent of the world's marine life and two-thirds of land animals were wiped from existence 252 million years ago by sudden changes to temperature, air and water conditions in what is called the "Great Dying".

Now researchers, led by staff at the University of Otago, have turned to ancient rocks to figure out why the recovery of life was delayed for more than five million years after the event.

Previous studies had concluded high levels of sulfur in water may have choked the return of life, but the new research - published in Nature Communications - looked at stones from Oman formed in an ancient ocean during the extinction and found no traces of the chemical.

Instead, they discovered totally different ingredients in the mix: too much iron and not enough oxygen.

Research lead Matthew Clarkson, from the University of Otago, said the finding suggested iron pollution in combination with lack of oxygen caused the longest recovery period in life on earth.

"We knew that the lack of oxygen in the oceans played a key role in the extinction and recovery processes, but we are still discovering how exactly it was involved, he said.

"Our findings about the chemistry of the ocean at the time provide us with a clearer picture of how this complex process delayed the recovery of life for so long."

They said it was possible run off from soil erosion caused by rising temperatures at the time may be a cause of the change in waters.

The researchers said they hoped the study would help scientists better understand the consequences of environmental change.

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