Scientists at Adelaide University in Australia have discovered evidence that the prehistoric Tethys Ocean may have formed the mountainous landscape of Central Asia during the Cretaceous period (145-66 million years ago).
The Tethys Ocean was a prehistoric ocean which disappeared during the Meso-Cenozoic period (the last 250 million years). It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasian inland marine basins (primarily today’s Black Sea and Caspian Sea).
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225 million years ago, India was a large island off the Australian coast, separated from Asia by the Tethys Ocean. The collision between this island and the Eurasian continent began approximately 50 million years ago.
“During the Cretaceous periods, dinosaurs would have seen a mountainous landscape as well, similar to the present-day Basin-and-Range Province in the western USA,” says co-author Stijn Glorie, who is an associate professor from Adelaide University’s School of Physics, Chemistry and Earth Sciences.
Previously, Central Asia’s mountainous landscape was thought to be linked to a mixture of tectonic activity, climate changes and dynamics within the Earth’s mantle over the past 250 million years. The new findings point to the Tethys Ocean as the main force, however.
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These mountain ranges would’ve formed thousands of kilometres away from the Himalaya collision zone, which is why the discovery is so astonishing. According to the researchers, it happened because of ocean crust sinking under the continent (which is called subduction) and “rolling back” – peeling away and sinking deeper.
This created enough tension inland to reactivate old fault lines in Central Asia into mountain ridges. Think of it like pulling on one end of a tablecloth and watching wrinkles appear far from where you’re pulling.
The researchers came to this conclusion using data analysis which combined thermal history models collected from more than 30 years of geological studies across the region. These models reveal how rocks cooled as they shifted closer to Earth’s surface during periods of mountain uplift and erosion.
According to Glorie, this research method could help scientists solve other geological mysteries across the world.
“There are many parts on the planet where the drivers and timing for mountain building and/or rifting are poorly understood. For example, closer to home, the break-up history of Australia from Antarctica is somewhat enigmatic,” he said.
“Australia drifted away about 80 million years ago, but there is no obvious imprint of this in the thermal history record of either the Antarctic or Australian plate margins. Instead, they record much older cooling histories.
“We are applying the same approach as used in Central Asia to advance understanding of Australia-Antarctica break-up.”
Read the full paper here: Deciphering mantle, tectonic and climatic drivers of exhumation
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Top image: Pamir Highway between the Ak-Baital Pass and Karakul in Tajikistan. Credit: Jean-Philippe Tournut/Getty Images
