Scientists Solved the Mystery of an Ancient Continent That Disappeared

Scientists have discovered the missing pieces of a long-lost continent that was once attached to Australia when dinosaurs roamed the planet, reports a new study. The scattered remains of this ancient landmass, known as Argoland, are buried underneath parts of Southwest Asian nations, such as Indonesia and Myanmar, opening a new window into the deep past of this dynamic region.

For decades, researchers have been puzzled by the disappearance of a huge 3,000-mile-long landmass, known as Argoland, that once bordered northwestern Australia some 155 million years ago, during the Jurassic era. 

Scientists know that Argoland existed because it created an immense patch of old seafloor as it moved north, known as the Argo Abyssal Plain. The tantalizing footsteps of this ancient landmass lead into Southeast Asia, but then the trail suddenly seems to go cold, with no sign of a huge continental chunk buried under the region. 

Now, Eldert Advokaat and Douwe van Hinsbergen, a pair of geologists at Utrecht University in the Netherlands, suggest that Argoland’s crust began to splinter into what they call an “Argopelago” of smaller islands as early as 300 million years ago, when Antarctica, South America, Africa, Australia, and India were part of a supercontinent called Gondwana. 

The researchers have now “identified the Gondwana-derived blocks and mega-units of Southwest Borneo, Greater Paternoster, East Java, South Sulawesi, West Burma, and Mount Victoria Land as fragments that collectively may represent fragments of Argoland,” according to a study published this month in Gondwana Research.

“The big thing is that we can now say that we know the amount of crust that was here, we know that it was really highly extended, and we can account for it in the geologic record that we find in Southeast Asia,” said Advokaat in a call with Motherboard. “We don't lose continents without a trace. We can still find them and that means that we can still make reasonably reliable reconstructions of what the Earth looked like back in the deep geological past.”

Advokaat began his quest to find the remains of Argoland about seven years ago while he was studying the origins of rocks on the Indonesian island of Sulawesi, and reconstructing the broader continental movements of this region across geological epochs. He teamed up on the project with van Hinsbergen, who previously discovered another lost Gondwanan continent, called Greater Adria, that is now buried 1,000 miles under Europe.  

With the help of newly released paleomagnetic observations, the team now believes they have solved the mysterious vanishing of Argoland. Previous attempts to find this continent in Southeast Asia were thwarted by the weirdly jumbled ages of rock in this region, which defy expectations of a single buried landmass. Advokaat and van Hinsbergen now propose that the continent was already a dynamic mix of islands and ocean basins when it split from Australia in the Jurassic, complicating the story of its northward drift. 

The lower parts of the Argopelago were eventually swallowed by the Sunda Trench subduction zone, a fault-line where the Indo-Australian continental plate is being pushed into Earth’s mantle by the Eurasian continental plate. During this process, some of the upper crust of the long-lost continent was “offscraped” onto land and seafloor that have survived to the present day. This backstory helps to explain how the remains of Argoland ended up stacked alongside other rock layers with surprisingly diverse ages.

“Only in small places, we have these kinds of windows where we can see that older crust material at the surface, and most of it is just covered by younger sediments,” Advokaat said. “It's very fragmented, but what is exposed gives you a lot of information.”

“The ultimate thing that we want to do is find out when the basins opened, which is when [Argoland] started to tear apart,” he continued. “That's what we're looking for. We are trying to peel off all these events of deformation, so it's really restoring it back to how it once looked.”

To that end, Advokaat plans to continue piecing together the geological puzzle of the region’s history, including the tale of how Argoland initially began to break apart at the dawn of the age of dinosaurs, and how it became embedded into the strata of Southeast Asia by the end of it.  

“It's quite a relief to have finally finished it,” Advokaat said, referring to the study. “But the truth is always temporary. The truth is what we know so far, until someone provides new knowledge and then we have to adjust it. So in that sense, it's a living thing. It's a living document.”