In what is a major international discovery, three Australian scientists have located the upturned remnants of what was once a giant underwater reef – with an escarpment 10 times higher than the Great Barrier Reef – in the Northern Flinders Ranges in outback South Australia.
The scientists are referring to the reef as Oodnaminta Reef, given it is located near an old hut called Oodnaminta Hut.
The reef is about 650 million years old and is the only known reef complex of this age anywhere in the world.
The next closest aged series of reefs found to-date are around 800 million years old and located in Arctic Canada.
And while they are yet to confirm it scientifically, the scientists – Jonathan Giddings, Associate Professor Malcolm Wallace, and Estee Woon from the School of Earth Sciences at the University of Melbourne – believe that peculiar fossils of possible multi-cellular organisms found in the reef could be the earliest examples of primitive animal life discovered to-date.
Their discovery is particularly significant because the reef existed for 5-10 million years during a period of tropical climate squeezed between two major ice age events where ice was present even at equatorial latitudes.
This extreme climate change from ice age to tropical conditions and back to ice age occurred approximately 750-550 million years ago (hundreds of millions of years before dinosaurs roamed the Earth) and is one of the most tumultuous climatic periods of Earth’s history.
"This reef is an internationally significant discovery because it provides a significant step forward in showing the extent of climate change in Earth's past and the evolution of ancient reef complexes – and it also contains fossils which may be of the earliest known primitive animals," Mr Giddings said.
"A lot of people will be intrigued as to why this once underwater reef is now located in a very barren part of inland Australia.
"At this stage in Earth's history, the eastern coast of Australia extended north from where the Flinders Ranges now lie.
"The eastern part of the Australian continent, from the Flinders Ranges through to the current eastern seaboard, was still buried under the ocean."
Associate Professor Wallace said that unlike the Great Barrier Reef, this reef was not made by coral.
"It was instead constructed by microbial organisms and other more complex organisms that have not been previously discovered," he said.
"The giveaway it is a reef is that there's a large mass of carbonate which forms when organisms have grown together in a complex framework.
"From a climate change point of view, this reef provides an important record of what was happening in the ocean 650 million years ago.
"The chemistry of the reef and other sediments forming in the ocean at the same time show the ocean was poorly mixed, and this may have had an effect on Earth’s climate at that time by allowing carbon to be trapped in the ocean’s depths."
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