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Mass die-off half a billion years ago caused by shifting tectonic plates, ancient rocks reveal




A major extinction in the midst of a huge expansion of life on Earth may have been driven by plate tectonics.

New research finds links between rock layers in Antarctica and Southern Australia, which at the time were part of the supercontinent Gondwana. This suggests that similar dynamics were occurring around the supercontinent roughly 513 million years ago: Mountains were uplifting, ancient reefs were dying, and eroded material from the continent was pouring into the sea. These moments in time coincide with the extinction known as the Sinsk event, said study leader Paul Myrow, a sedimentologist at Colorado College.

"Oddly, it was tectonics that triggered an extinction," Myrow told Live Science.

The Sinsk event occurred during the Cambrian period (540 million to 485 million years ago), which saw a huge diversification of life on Earth known as the Cambrian explosion.

But in the middle of this flourishing, the Sinsk extinction killed off several major groups, including cone-shelled Animals called hyoliths and sponges called archaeocyathids, which once built enormous reefs all over the globe. Researchers know that the Sinsk event was linked to falling levels of oxygen in the oceans, but they haven't been able to pinpoint the precise cause.

Related: The 5 mass extinction events that shaped the History of Earth — and the 6th that's happening now

A map showing the positions of Australia and Antarctica in the Gondwanan supercontinent. (Image credit: Paul Myrow, Science Advances)

Now, Myrow and his colleagues say they have the answer. The tectonics of Gondwana, which formed between 600 million and 540 million years ago, triggered a series of events that drowned the archaeocyathid reefs and altered the oceans, they reported March 29 in the journal Science Advances.