Geochemical analysis of Chinese rocks used to better understand the Permian-Triassic mass extinction

Oct 16, 2012 by Greg Hand
Field photograph of the Permian-Triassic boundary (PTB) section at Xiakou, Hubei Province, South China.

(Phys.org)—University of Cincinnati professor Thomas J. Algeo, working with a team of Chinese scientists, has established a tight link between repeated episodes of volcanic activity and environmental degradation leading up to the deadliest extinction in Earth's history.

In a paper published in the November 2012 issue of the journal Geology, Algeo and colleagues from the China University of Geosciences track patterns of ratios associated with volcanic ash layers preserved in . In particular, the team looked at two rock successions preserving finely layered marine deposits that record from before the end of the (252 million years ago) through the early part of the next geologic period, the Triassic. These successions contain layers recording events during the crisis that resulted in the extinction of some 90 percent of marine species on Earth.

"These sections have not been studied in detail geochemically," Algeo said. "Because they are deep-marine deposits, they record a very detailed and complete sequence of events. This is something you generally don't find in terrestrial or shallow-marine rocks."

The evidence, Algeo said, demonstrates a volcanic cause of the end-Permian crisis. Volcanic activity contributed to the that accompanied the main extinction horizon at the end of the Permian.

Some researchers have hypothesized that the biotic crisis and were caused by the , a large flood basalt province that erupted approximately 252 million years ago, coinciding more or less with the mass extinction. "This connection has been inferred on the basis of similarities in age and, thus, is circumstantial," Algeo said.

"We demonstrate for the first time that the Permian-Triassic biotic crisis was probably triggered by enormous explosive volcanic eruptions," Algeo said. "We suspect that the ash layers in the Chinese PTB sections are linked to the Siberian Traps, although more research will be needed to verify this."

At the heart of their analysis, the co-authors identify significant changes in the ratio of carbon isotopes at each ash layer in the Chinese sections. This implies large releases of isotopically light, organically derived carbon dioxide or methane with each eruptive event. "This is consistent with large-scale injection of magma into the organic-rich sediments of the West Siberian coal province," Algeo said.

According to Algeo, the Chinese deposits have to potential to clarify the mechanisms that almost wiped out all life on Earth 252 million years ago, and to help in better constraining the timing of the Siberian Traps eruptions.

In earlier research at a variety of locations around the globe, Algeo had compiled evidence that the Permian-Triassic extinction, unlike the more famous Cretaceous-Tertiary extinction in which the large dinosaurs went extinct, was a gradual process. The final extinction event may have been preceded by hundreds of thousands of years of environmental stress. The China research supports this hypothesis of gradual steps toward a dramatic extinction event. The accumulating evidence, he said, points to a very different mechanism, and a far more devastating result, than the end-Cretaceous bolide impact.

"It's becoming clear that almost every mass extinction has a different cause," Algeo said.

Explore further: Aging Africa

More information: geology.gsapubs.org/content/current

Related Stories

Global extinction: Gradual doom is just as bad as abrupt

Feb 03, 2012

A painstakingly detailed investigation shows that mass extinctions need not be sudden events. The deadliest mass extinction of all took a long time to kill 90 percent of Earth's marine life, and it killed ...

Algeo tracks evidence of 'The Great Dying'

Oct 28, 2010

More than 251 million years ago, at the end of the Permian period, Earth almost became a lifeless planet. Around 90 percent of all living species disappeared then, in what scientists have called "The Great Dying."

Recommended for you

Aging Africa

Aug 29, 2014

In the September issue of GSA Today, Paul Bierman of the University of Vermont–Burlington and colleagues present a cosmogenic view of erosion, relief generation, and the age of faulting in southernmost Africa ...

NASA animation shows Hurricane Marie winding down

Aug 29, 2014

NOAA's GOES-West satellite keeps a continuous eye on the Eastern Pacific and has been covering Hurricane Marie since birth. NASA's GOES Project uses NOAA data and creates animations and did so to show the end of Hurricane ...

EU project sails off to study Arctic sea ice

Aug 29, 2014

A one-of-a-kind scientific expedition is currently heading to the Arctic, aboard the South Korean icebreaker Araon. This joint initiative of the US and Korea will measure atmospheric, sea ice and ocean properties with technology ...

User comments : 0