Friday, 18 November 2011

The Exact Time Frame Of The Permian Great Dying Has Been Established

Charles Henderson (middle) and his team collect
samples at Shangsi in the Sichuan Province, China
The Great Dying was, of course, the greatest extinction in Earth history: 98% of marine life and 78% of terrestrial life became extinct. This last figure was recently established in an exhaustive study of all known species before and after the extinction event boundary. Yet many other aspects to this single destructive event remain a unclear, such as when did the event start  and end, and how fast did it progress?

Palaeontologists and geologists have been able to estimate roughly the extinction event by closely examining the layers of rock. Yet the exact cut-off point was difficult to identify due to natural global irregularities in the fossil record. Now a team from Universities in North America and Chain, led by Dr Charles Henderson from the University of Calgary's department of Geoscience have, for the first time, accurately pinned down statistics of this giant extinction event.

They took well preserved samples of sediment from formations spanning a geographical range from China to Tibet. By combining this with fossil data, they found that the extinction event peaked some 252.28 million years ago over a period of 20,000 year, with a maximum extinction date range of 200,000 years. They believe that the primary cause, based upon geochemical analysis of the sediment, was a vast release of carbon dioxide from super-massive marine lava flows which occured in what is now Siberia.

'Our information narrows down the possibilities of what triggered the massive extinction and any potential kill mechanism must coincide with this time. These dates are important as it will allow us to understand the physical and biological changes that took place.' says 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.'