Clues to largest mass extinction
TWO INTERNATIONAL studies should help fill in the picture of what was happening in the oceans and on land just before, during and after the most extreme extinction in Earth's history, the Permian-Triassic extinction.
Approximately 90 per cent of all marine species and 70 per cent of all land species disappeared at the Permian-Triassic boundary, roughly 250 million years ago, but the cause of this extinction event is still unknown.
Kliti Grice and colleagues studied organic compounds and sulphur isotopes in sediment cores drilled off the coasts of Australia and China.
The results published in Science suggest that the upper ocean was extremely low in oxygen and thus hospitable to bacteria that use sulphur compounds for energy.
The authors say their findings are consistent with the idea that sulphide poisoning in the ocean and emissions of hydrogen sulphide to the atmosphere were important drivers of extinction.
A second study pieces together the vertebrate fossil record on land, finding that a period of gradual change led to a final extinction pulse. The extinction pulse particularly affected large reptiles called Dicynodont therapsids.
— Our Bureau
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