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Piece of North American continent found in northern Australia

"This new finding is a key step in understanding how Earth's first supercontinent Nuna may have formed," researcher Zheng-Xiang Li said.

By Brooks Hays
Piece of North American continent found in northern Australia
The missing continent became mixed up during the formation and breakup of the supercontinent called Nuna. Photo by Bjoertvedt/Wikimedia/CC

Jan. 24 (UPI) -- Earth's continents are like a jigsaw puzzle that's constantly being rearranged. Sometimes, during the reshuffling, pieces get misplaced.

According to scientists at Curtin University in Australia, a portion of Queensland is one of those misplaced pieces, having originally been a part of North America some 1.7 billion years ago.

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Researchers first became clued into the mix-up after discovering that rocky deposits a few hundred miles west of the city of Cairns featured geologic patterns similar to rocks found in Canada.

"Our research shows that about 1.7 billion years ago, Georgetown rocks were deposited into a shallow sea when the region was part of North America," doctoral student Adam Nordsvan said in a news release. "Georgetown then broke away from North America and collided with the Mount Isa region of northern Australia around 100 million years later."

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The continental chunk's misplacement occurred during the reorganization of puzzle pieces that yielded the supercontinent Nuna.

"The team was able to determine this by using both new sedimentological field data and new and existing geochronological data from both Georgetown and Mount Isa to reveal this unexpected information on the Australia continent," Nordsvan said.

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When Nuna broke up 300 million years after it formed, the Georgetown rocks stayed attached to Australia, while the rest of North America drifted away.

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The research suggests the mountains in the Georgetown region are the product of two collisions: an initial collision in North America, between Georgetown and Mount Isa, and a second collision in Australia, between Georgetown and the Australian mainland.

"Ongoing research by our team shows that this mountain belt, in contrast to the Himalayas, would not have been very high, suggesting the final continental assembling process that led to the formation of the supercontinent Nuna was not a hard collision like India's recent collision with Asia," said Zheng-Xiang Li, a professor of earth science at Curtin. "This new finding is a key step in understanding how Earth's first supercontinent Nuna may have formed, a subject still being pursued by our multidisciplinary team here at Curtin University."

The research, which involved the help of scientists from Monash University and the Geological Survey of Queensland, was published in the journal Geology.

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