Icebergs bombed by asteroids 600mn-yrs-ago ‘created early life’

Wednesday, October 20, 2010

WASHINGTON - University of Adelaide researchers have found evidence of ancient icebergs mixed in with volcanic rocks, which were spewed out when an asteroid hit the Earth between 635-542 million years ago.

The discovery of blocks of gravel, which sank to the bottom of the sea trapped in ancient icebergs, has sparked a new understanding of a bizarre group of creatures.

Associate Professor Victor Gostin and colleagues said that the impact of the 4.7-kilometer (2.9-mile) asteroid - which left a 90-kilometer (55.9-mile) crater in what is now Lake Acraman in the Gawler Ranges of South Australia - occurred during a period of extreme cold.

This contradicts previous ideas which suggest the impact of the asteroid actually precipitated a period of glaciations, Gostin said.

“Icebergs carry coarse debris, boulders and grains. As the iceberg melts it is dragged to the bottom by the weight of the debris, then the ice melts and the surrounding mud eventually buries the debris, creating this sort of fossilized iceblock,” Discovery News quoted Gostin as saying.

“So when you find coarse boulders embedded in fine deposits, something must have rafted it there — in this case, an iceberg,” he added.

Professor Malcolm Walter of the University of New South Wales described the effect of the icy climate and asteroid impact as a “double whammy” that paradoxically led to the “flourishing of exotic plankton and the first macroscopic animals”.

The Ediacaran fauna were the first large complex life forms to appear. They resembled jellyfish, sponges, marine worms, plus other organisms whose body plan resembles nothing alive today.

Gostin’s team will explore other glacial deposits that formed around the same time in other parts of the world to see if there is further evidence of the asteroid’s impact on the microscopic creatures at that time.

The research is published in the Australian Journal of Earth Sciences. (ANI)

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