Friday , October 22 2021

Lost for 12,000 years, the hidden island of Cooloola produces secrets


The ancient parabolic dunes of the Cooloola Sand Mass Region form much of the landscape between Noosa Heads and the northern tip of Fraser Island.

Now Sydney University PhD student Tiago Passos believes that a lost island with the same dune formations may have been found at Barwon Bank, giving scientists a unique opportunity to confuse what may be the original Fraser Island and precursor of the unique landscape. of Cooloola.

Our lost sand island, recreated from images of the bottom of the sonar off the coast of Cooloola.

Our lost sand island, recreated from images of the bottom of the sonar off the coast of Cooloola. Contributed

Lost for 12,000 years and just 40km from Rainbow Beach, an Ice Age sand island was discovered, incredibly well preserved and about 60m below.

Passos says the training he is researching would have been "just like Fraser Island."

And as Fraser Island, increasingly known by its Aboriginal name, K? Gari (which means paradise), it may also have been inhabited.

The 70 km stretch of dunes seems to have survived surprisingly intact, despite being swallowed by the ocean. Passos is one of the researchers who investigate this.

It is believed that the lost ancestor of our Cooloola coast has been preserved under the ocean because of its chemical composition, which includes calcium compounds.

It is believed that these may have formed a kind of cement when subjected to rain, weather and other geological processes.

That would mean that the dunes became stone before being submerged by the rising seas that followed the last Ice Age.

The work of Passos is part of the effort to explain the dunes, which survived almost like an ancient sculpture of petrified sand.

"The place would have been an island just like Fraser Island, surrounded by water, but 40 kilometers from the current coast," Passos said.

The 70-km-long stretch of dunes, deep in the sea between the Fraser and Moreton Islands, baffled scientists who believe it should have been destroyed by the action of waves and tides as the waters rose around it.

"I find the mechanism that made them so well preserved intriguing," Passos said.

The study of the dune researcher led to the publication of his work in the prestigious geology Australian Earth Science Magazine.

Passos says that sonar images revealed the shape and extent of the preserved landscape of the dunes.

Humans are believed to have established themselves long ago on the Australian continent at the driest, coldest time, when the island was still above water, along with many plants and animals still extant.

The hardening of the dunes may have preserved a foot or paw print. And these impressions can still be preserved in some places.

"After the dunes hardened, walking on them would be like walking on a rock," Passos said recently.

He said the dunes were discovered by an expedition to the Great Barrier Reef, which mapped the seabed at a site called Barwon Bank on Fraser Shelf, 50 km north of the island of Moreton.

The sonar image captured submerged curved structures, which were originally thought of as part of an ancient reef.

Passos analyzed the images and samples and found that they were rock-like structures.

And though the calcium may have come from a reef, the lost island was not in itself a reef. It was shaped by the wind, just like Fraser Island.

But, unlike Fraser Island, the submerged dunes are largely composed of calcium carbonate (instead of the silica sand of Fraser Island).

They are up to 15 meters high, according to marine geologist James Daniel of James Cook University.

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