Tectonic shifts caused mass extinction after “Cambrian explosion”

Geological studies of sites in Australia and Antarctica reveal the series of tectonic events which caused a mass extinction more than 500 million years ago.

The new research helps explain the million-year relationships between geological processes, climate change and extinction.

Half a billion years ago, life on Earth rapidly expanded in a period known as the “Cambrian explosion.” The fossil record from the Cambrian period (539–485 million years ago) shows the sudden emergence of a plethora of new species, including all the major body plans of animals we still see today.

At the end of the Cambrian, however, 40% of life on Earth vanished in a major extinction event.

Entire animal lineages such as archaeocyathids (reef-building sponges) and hyoliths (animals with small, conical shells) were lost at the end of the Cambrian.

New research published in the journal Science Advances might explain the Earth-shaking processes that led to the end-Cambrian mass extinction.

“It’s unusual to point to a tectonic cause for an extinction event, but the evidence is compelling,” says corresponding author John Goodge from the University of Minnesota Duluth in the US.

During the Cambrian, the authors of the paper say, a contraction of the crust along the edge of the ancient supercontinent Gondwana led to a “series of geodynamic, palaeoenvironmental, and biotic changes” including a loss of shallow marine habitats; the release of large amounts of greenhouse gases; and rapid climate change.

The scientists’ analysis is based on fieldwork beginning in the 1990s geological records from Nimrod Glacier in Antarctica. These results were compared to those obtained beginning in 2011 on Kangaroo Island in South Australia.

Tents in antarctica
Field camp on Errant Glacier in the central Transantarctic Mountains. Credit: John Goodge.

The two sites today are separated by more than 5,000 km. More than half a billion years ago, they were right next to each other and near the equator. They share near-identical records of mountain-building events just before the end-Cambrian extinction.

Examining trilobite fossils, they were able to pinpoint the habitat collapse and extinction.

“You never know when something you did decades ago is going to come together in a new way,” Goodge adds.

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