Ancient lost ocean may have built Central Asia’s dinosaur-era mountains

 A new study from Adelaide University suggests that the ancient Tethys Ocean played a major role in shaping Central Asia's landscape during the Cretaceous period, long before the rise of the Himalayas.

The research team reached this conclusion through a large-scale data analysis that combined hundreds of thermal history models collected from more than 30 years of geological studies across Central Asia.

Scientists have often linked the region's landscape to a combination of tectonic activity, climate changes, and processes deep within Earth's mantle over the past 250 million years. However, the new findings point to a different dominant force.

"We found that climate change and mantle processes had only little influence on the Central Asian landscape, which persisted in an arid climate for much of the last 250 million years," said Dr. Sam Boone, who was a post-doctoral researcher at Adelaide University when the research was conducted.

"Instead, the dynamics of the distant Tethys Ocean can directly be correlated with short-lived periods of mountain building in Central Asia."

How a Lost Ocean Influenced Mountain Building

The Tethys Ocean once stretched across a vast area of the planet before gradually disappearing during the Meso-Cenozoic period, which covers the last 250 million years. Today, the Mediterranean Sea is considered the final remnant of that ancient ocean.

"The present-day relief of Central Asia was largely built by the India-Eurasia collision and ongoing convergence," said co-author Associate Professor Stijn Glorie, from Adelaide University's School of Physics, Chemistry and Earth Sciences.

"However, 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.

"It is thought that the extension in the Tethys, due to roll-back of subducting slabs of ocean crust, reactivated old suture zones into a series of roughly parallel ridges in Central Asia, up to thousands of kilometers away from the Himalaya collision zone."

According to the researchers, geological activity connected to the ancient ocean may have triggered mountain formation far from the actual plate boundaries.

Thermal History Models Reveal Earth's Past

The study relied on thermal history models, which help scientists trace how rocks cooled as they moved closer to Earth's surface during periods of mountain uplift and erosion.

"These models were constructed using thermochronology methods and reveal how rocks cooled down when they are brought towards the surface during mountain uplift and subsequent erosion," Associate Professor Glorie said.

"We analyzed a compilation of thermal history models in function of plate-tectonic models for the Tethys Ocean evolution, as well as deep-time precipitation and mantle-convection models."

By combining these datasets, the team was able to reconstruct previously hidden chapters of Earth's geological history.

Applying the Research Beyond Central Asia

Associate Professor Glorie said the same research method could help scientists investigate other geological mysteries around the world. The study was published in Nature Communications Earth and Environment.

"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."

Source: ScienceDaily