A little later than 2 billion years, the world had almost finished assembling a supercontinent by the name of Nuna (or Columbia). Much of the continental mass we see today was spliced together in a gigantic puzzle piece, including Laurentia and Australia.
Then, 1.7 billion years ago, the Georgetown Inlier pieces were then deposited in an epicontinental rift, a sea or ocean overlying a massive continental shelf. A growing chasm began to tear the Georgetown Inlier away from Laurentia around 1.66 billion years ago, leaving a volcanic arc in its wake.
Around this time, Nuna itself gradually began to self-destruct, break up, and rift apart.
By around 1.6 billion years ago, as Laurentia made its way northwards, this tiny Inlier refused to tag along, and instead remained behind and collided with northern Australia.
“The Georgetown block crossed an ocean similar to how India did before colliding with Asia,” lead author Adam Nordsvan, a PhD student at CU, told IFLScience. “It’s a fantastic finding.”
He describes the Georgetown Inlier as a “continental ribbon,” a rather beautiful term for “a piece of continental crust that has rifted from a craton,” in this case Laurentia.
“New Zealand is a modern example of this,” he added.
Although this isn’t the first paper to suggest that parts of Australia could in fact be imposters from Laurentia, it is the first to definitely conclude this. Now we know a little more about the story of a long-lost supercontinent, one that’s baffled researchers ever since its chaotic jigsaw pieces were first discovered.