Researchers pinpoint date, rate of Earth’s most extreme extinction

By: Bill Graveland, The Canadian Press
Posted: 11/17/2011 1:14 PM | Last Modified: 11/17/2011 2:47 PM

Charles Henderson (middle) of the University of Calgary collects material from a sedimentary layer in Shangsi, Sichuan Province, China. This was one of more important sections studied for ash layers and marine fossils used to pinpoint the dates and rate of Earth's massive extinction. It's not exactly down to the day, month and year, but researchers are closer to pinpointing when most life on our planet became extinct.THE CANADIAN PRESS/HO-Charles Henderson

CALGARY – It’s not exactly down to the day, month and year, but researchers are closer to pinpointing when most life on our planet became extinct.
About 95 per cent of marine life and 70 per cent of terrestrial life became extinct about 250 million years ago when continents were all one land mass called Pangea.

A team of scientists from North America and China published a paper this week in Science which narrows down both the date and the rate of extinction.
“It may sound like it’s not very high resolution … when you compare it to the things we do today, but in terms of geological studies this is as precise as we’ve ever gotten to this point,” Charles Henderson, a professor in the geoscience department at the University of Calgary, said in an interview with The Canadian Press.

The extinction was originally believed to have occurred 251.4 million years ago. Henderson, who is a co-author of the paper, said the new estimate pegs it as happening earlier than that — about 252.2 million years ago.

The study also concludes that extinctions of most marine and terrestrial life took place simultaneously. The trigger was probably a massive release of carbon dioxide from volcanic flows in northern Russia.

“Our information narrows down the possibilities of what triggered the massive extinction and any potential kill mechanism must coincide with this time.”
Henderson’s part in the research involved the study of micro fossils. He said the tiny teeth of an extinct eel-like animal provided a relative time scale on everything from hydrocarbon deposits to global extinctions.

Other colleagues examined stable carbon isotopes. A third study involved high-resolution geo chronology. Henderson said his colleagues examined tiny crystals of zircon found within ash beds which are like “little time capsules” and hold in radioactive decay.

The analysis of various types of dating techniques on well-preserved sedimentary sections from South China to Tibet helped researchers determine when the mass extinction peaked and that it covered a span of less than 200,000 years. Most of the extinction occurred within about 20,000 years.

“These dates are important as it will allow us to understand the physical and biological changes that took place,” said Henderson.

“We do not discuss modern climate change, but obviously global warming is a biodiversity concern today. The geologic record tells us that ‘change’ happens all the time, and from this great extinction life did recover.”

via Researchers pinpoint date, rate of Earth’s most extreme extinction – Winnipeg Free Press.

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