Monday, 22 March 2010

Fossil clues from the world's biggest extinction event, the ‘Great Dying' of 251 million years ago, will throw light on our present climate dilemma, according to a researcher from The University of Western Australia.

Dr Zhong Qiang Chen, an Australian Research Fellow at UWA's Centre for Petroleum Geoscience, is the lead researcher on a $570,000 Australian Research Council Discovery project: Reconstruction of marine ecosystems following the greatest mass extinction of Earth life: Lesson for the present .

Dr Chen and his team are studying the much delayed recovery of marine species after the ‘Great Dying' by examining fossils around the world, particularly in his native South China, which, during the Triassic, enjoyed a temperate climate and was the site of a major re-flourishing of microfloras, then invertebrates and vertebrates following an order from low to high levels comparable to modern ecosystems.

The ‘Great Dying' at the end of the Permian period saw more than 90 per cent of marine species wiped out by likely basalt volcanic eruption that pumped massive volumes of greenhouse gases into the air and acidified the oceans.  This extinction event impacted organisms and ecosystems more severely than the younger crisis which killed all dinosaurs 65.5 million years ago at the end of the Cretaceous period, when up to 75 per cent of marine species died out.

However, without the 20 small and five major extinction events that occurred in the distant past, life as we know it would not exist.

The ‘Great Dying' is best recorded in South China.  In some places, the rocks below the layer of volcanic ash deposited during the ‘Great Dying' abound with fossils of plants and animals, but the rocks above the layer have no fossils at all.  "In fact, the Perth Basin in WA also records the complete process of marine ecosystems' collapse and rebuilding during the ‘Great Dying' and its aftermath," Dr Chen said.  "This site provides a unique window on how marine life reacted to the ‘Great Dying' in the southern high-latitude Gondwanaland, with Australia as the core."

Dr Chen has recently returned from a field trip to Oman where, as president of a series of UNESCO geoscience workshops, he led an international group into the Hajar Mountains to examine the rocks and the geological boundary of the Triassic and Permian periods, clearly delineated by the colours of the rocks.

"I started being interested in fossils as a boy growing up in an iron-mining town.  The iron had been preserved in the Triassic rocks," Dr Chen said.  "I'd find a small seashell fossil and be amazed at its similarity to a modern one.

"We are now looking at the fossil record globally, comparing the ecosystems in Earth deep time with today's ecosystems that are also facing the same disasters such as elevated CO2 content, global warming, volcanic eruption and some chemical pollution events.  Ultimately, we hope to recognise what types of ecosystems were fragile and easily collapse in the ‘Great Dying' and what kinds of ecosystems were able to easily recover in the aftermath.  This will provide information for the management of modern ecosystems," Dr Chen said.

Dr Chen chairs an International Geological Correlation Program working on the ‘Great Dying' and its aftermath, sponsored by the International Union of Geological Sciences and United Nations Educational, Scientific and Cultural Organisation.

Media references

Dr Zhong Qiang Chen (+61 8)  6488 1924
(UWA School of Earth and Environment)
Janine MacDonald (UWA Public Affairs)  (+61 8)  6488 5563  /  (+61 4) 32 637 716


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