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Scientist Sophie Newbury studies the "dead zone," a rock layer in Karoo Basin.
Courtesy of Robert Gastaldo, Colby College

Geologic Findings Undermine Theories of Permian Mass Extinction Timing
News story originally written on March 2, 2009

Tens of millions of years before dinosaurs roamed Earth, their ancestors were all but eliminated in a catastrophic event called the Permian Mass Extinction. This was the greatest extinction event ever in Earth's history! The Permian period extended from 299 to 252.6 million years ago.

Geologists have made some discoveries that call into question popular theories about this Extinction.

Before, scientists thought they had found a distinct record of the Permian Mass Extinction in sedimentary rocks found across southern hemisphere continents. There was actually a layer in the rocks that scientists called the "dead zone" because of the lack of plant and animal fossils found there.

But recent work done in the Karoo Basin in central South Africa, where the best fossils records from the Permian time period are found, shows conflicting evidence in the layers of rock found.

They discovered that this dead zone layer is not found at the same physical position in the rock record at all places, even across a land area 1 kilometer across. As such, it is not a reliable marker of the mass extinction of terrestrial animals.

Lead geologist on this project, Robert Gastaldo, says that the research proves that "there is no evidence to support a terminal extinction event in the record of the Karoo Basin, based on the criterion of an unique event bed or dead zone."

Last modified June 11, 2009 by Jennifer Bergman.

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