Tuesday, December 17, 2013

Siberian Traps Geochronology Tied VERY Tightly to Permian Triassic Exinction

Geology is partly detective work, and scientists now have enough evidence to book a suspect in the biggest environmental catastrophe in Earth's history.

Painstaking analysis of rocks from China and Russia prove the culprit is a series of massive volcanic eruptions, which flooded ancient Siberia with thick lava flows just before Earth's worst mass extinction almost 252 million years ago, researchers said here yesterday (Dec. 11) at the annual meeting of the American Geophysical Union. Thanks to new computer models of the eruption's devastating effects, and detailed mapping of rocks deposited around the time of the mass dying, researchers now have their best case ever for pinning the extinction on the enormous lava outpouring.

The eruptions — now called the Siberian Traps — lasted less than 1 million years but left behind Earth's biggest "large igneous province," a pile of lava and other volcanic rocks about 720,000 cubic miles (3 million cubic kilometers) in volume. More than 96 percent of marine creatures and 70 percent of land species perished at the end of the Permian Period, versus 85 percent of life in the later dinosaur-killer extinction. In the Permian, all trilobites died out, along with 97 percent of the gorgeous marine creatures called ammonites. Sharks, fish and reptiles were hard hit.

"We can resolve the timing of the Siberian Traps and show that magmatism did precede the onset of mass extinction," said Seth Burgess, an MIT geochemistry graduate student who presented some of the research here.

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