Leading palaeontologist speaks on evolutionary change
One of Australia's most recognised and respected palaeontologists has been invited to speak at the 116th annual meeting of the Geological Society of America.
Dr Kath Grey, who has been resident palaeontologist for more than 30 years at the West Australian Department of Industry and Resources' Geological Survey Division, will present the results of her studies of an asteroid impact that occurred at Lake Acraman in South Australia about 580 million years ago.
Dr Grey's results suggest that the event, known as the "Acraman impact", may have set the scene for the so-called "Cambrian explosion", one of the biggest evolutionary changes in the geological record.
"My evidence contradicts parts of the widely accepted 'Snowball Earth' theory, which claims that evolutionary changes resulted from a devastating ice age, when ice sheets completely covered the earth some 600 million years ago," Dr Grey said.
"Instead, it seems that the aftermath of an almost five kilometre diameter asteroid impact may have revolutionised the nature of life on earth. The impact itself would have created a crater about 90 kilometres in diameter.
"To put this in context, the asteroid would have been bigger than the Perth CBD and the crater would have extended from Rockingham, through Mundaring to Joondalup and Rottnest; the debris would have scattered beyond Geraldton, Mount Magnet, Merredin and Albany."
According to Dr Grey, the consequences of the impact would have been felt globally, with the main effect being the production of an enormous dust cloud.
"This dust cloud reached the stratosphere, blocking out sunlight and preventing photosynthesis, possibly for several months or even years," Dr Grey said.
"Life forms were fairly primitive at the time of the impact, however it seems to have severely affected the bacteria and simple algae that were the main components of the biota.
"As life began to recover from the event, new and more advanced forms of algae took over the vacant niches and evolved rapidly. Some of these new organisms belonged to types known to generate oil and gas in younger rocks and many played a significant role in increasing the amount of oxygen in the atmosphere.
"They formed the base of the food chain that allowed animals to evolve, so the changes that took place had a profound effect on later evolution."
About 6500 people will be at the Geological Society of America's meeting and Dr Grey is looking forward to presenting her findings to them.
"Many of the participants are from North America and I think they will include some of our biggest critics," Dr Grey said.
"Proponents and supporters of the 'Snowball Earth' theory will probably be there, so it will be interesting to hear their reaction.
"However, the meeting will provide an important forum to showcase and defend a significant piece of Australian scientific research."
Dr Grey graduated from Sheffield University in England in 1971 before she joined the Geological Survey of Western Australia, part of the Department of Industry and Resources. Her preliminary studies on the evolution of the algae 600 million years ago formed part of her PhD studies, completed in 1999 at Macquarie University in New South Wales, where she is also an Associate Researcher with the Australian Centre for Astrobiology.
Her work has greatly improved science's understanding of ancient life on earth including being instrumental in discovering some of the most convincing evidence of the earth's oldest fossilised stromatolites - near Marble Bar in the Pilbara region of Western Australia.
In 2003 she was awarded one of the Geological Society of Australia's highest accolades, the Gibb Maitland Medal, in recognition of her world-class contribution to palaeontology and micropalaeontology and understanding of Western Australia's geology.
The 116th annual meeting of the Geological Society of America will be held at the Colorado Convention Centre in Denver from 7-10 November 2004.
© 2005 The Geological Society of America