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1.7-Billion-Year-Old Chunk of North America Found Sticking to Australia

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« on: January 23, 2018, 05:47:01 pm »

1.7-Billion-Year-Old Chunk of North America Found Sticking to Australia
By Megan Gannon, Live Science Contributor | January 22, 2018 01:59pm ET


       


1.7-Billion-Year-Old Chunk of North America Found Sticking to Australia
This diagram shows the Georgetown terrane, in green, joining Australia around 1.6 billion years ago during the formation of the supercontinent Nuna.
Credit: Geology, https://doi.org/10.1130/G39980.1

Geologists matching rocks from opposite sides of the globe have found that part of Australia was once attached to North America 1.7 billion years ago.

Researchers from Curtin University in Australia examinedrocks from the Georgetown region of northern Queensland. The rocks sandstone sedimentary rocks that formed in a shallow sea had signatures that were unknownin Australia but strongly resembled rocks that can be seen in present-day Canada.

The researchers, who described their findings online Jan. 17 in the journal Geology, concluded that the Georgetown area broke away from North America 1.7 billion years ago. Then, 100 million years later, this landmass collided with what is now northern Australia, at the Mount Isa region. [Photo Timeline: How the Earth Formed]

"This was a critical part of global continental reorganization when almost all continents on Earth assembled to form the supercontinent called Nuna," Adam Nordsvan, Curtin University doctoral student and lead author of the study, said in a statement.

Nordsvan added that Nuna then broke apart some 300 million years later, with the Georgetown area stuck to Australia as the North American landmass drifted away.
These rocks found around Georgetown, Australia, are made from sediments originally deposited off the coast of present-day Canada.
These rocks found around Georgetown, Australia, are made from sediments originally deposited off the coast of present-day Canada.
Credit: Geology, https://doi.org/10.1130/G39980.1

The continents as we know them today have shifted places throughout Earth's 4-billion-year history. Most recently, these landmasses came together to form the supercontinent known as Pangaea about 300 million years ago. Geologists are still trying to reconstruct how even earlier supercontinents assembled and broke apart before Pangaea. Scientists first proposed the existence of Nuna, Earth's first supercontinent, in 2002. Nuna is sometimes called Columbia.

Previous research suggested that northeast Australia was near North America, Siberia or North China when the continents came together to form Nuna, Nordsvan and colleagues noted, but scientists had yet to find solid evidence of this relationship.

Colliding landmasses can form mountain ranges. For example, the clash of the continental plates of India and Asia about 55 million years ago created the Himalayas. The researchers of the new study say they found evidence of mountains forming when Georgetown rammed into the rest of Australia.

"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,"Zheng-Xiang Li, a co-author of the study and a professor of Earth science at Curtin University, said in the statement.

Original article on Live Science.
https://www.livescience.com/61490-chunk-of-north-america-in-australia.html
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Brave New World
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« Reply #1 on: January 23, 2018, 05:48:03 pm »

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« Reply #2 on: January 23, 2018, 05:48:32 pm »

Earth's continents were laid out very differently in the distant past. Image Credit: CC BY-SA 3.0 NikoLang
Scientists have identified an area of Australia that broke away from North America 1.7 billion years ago.
The region in question, which today is known as Georgetown, is home to sandstone sedimentary rocks found nowhere else in Australia but that closely resemble rocks found in present-day Canada.

Researchers from Curtin University concluded that the whole area must have broken away from North America around 1.7 billion years ago before colliding with what is now northern Australia.

"This was a critical part of global continental reorganization when almost all continents on Earth assembled to form the supercontinent called Nuna," said doctoral student Adam Nordsvan.

When Nuna broke apart again 300 million years later, the Georgetown region remained attached to Australia as the North American landmass drifted away.

The discovery is important because it not only reveals more about Australia's history but also provides further clues as to the shape of the Nuna supercontinent and how all the landmasses fitted together.

Evidence was also found to suggest that Georgetown's mountain range also formed around this time.

"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 study co-author Zheng-Xiang Li.
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