New research from the University of Adelaide suggests that the ancient Tethyan Sea played a major role in shaping the landscape of Central Asia during the Cretaceous period, long before the rise of the Himalayas.
The research team reached this conclusion through extensive data analysis combining hundreds of thermal history models collected from more than 30 years of geological surveys across Central Asia.
Scientists often link the region’s landscape to a combination of tectonic activity, climate change, and processes deep in the Earth’s mantle over the past 250 million years. But new discoveries show there’s another dominant force.
“We found that climate change and mantle processes have had little impact on the landscape of Central Asia, which has had an arid climate for most of the past 250 million years,” said Dr Sam Boon, a postdoctoral fellow at the University of Adelaide at the time the study was conducted.
“Rather, the dynamics of the distant Tethys Ocean may be directly correlated with short-term mountain building in Central Asia.”
How did the lost ocean influence mountain construction?
The Tethys Ocean once extended over vast areas of the Earth, but gradually disappeared during the Mesocene Era over the past 250 million years. Today, the Mediterranean Sea is considered the last vestige of an ancient sea.
“The present-day relief of Central Asia was largely built on collision and ongoing convergence between India and Eurasia,” said co-author Associate Professor Stein Glory, from the School of Physics, Chemistry and Earth Sciences at the University of Adelaide.
“However, during the Cretaceous period, dinosaurs may have also seen mountainous landscapes similar to the present-day Basin and Range states of the western United States.
“Expansion of the Tethyan Mountains by unwinding of a slab of subducting oceanic crust is thought to have reactivated an old suture zone from the Himalayan collision zone into a series of near-parallel ridges in central Asia up to several thousand kilometers away.”
Researchers say geological activity related to ancient oceans may have led to the formation of mountains far from the actual plate boundaries.
Thermal history models reveal Earth’s past
The study relied on thermal history models that help scientists track how rocks cool as they approach the surface during periods of mountain uplift and erosion.
“These models are built using thermochronology techniques to reveal how rocks cool as they are transported toward the surface during mountain uplift and subsequent erosion,” Associate Professor Glory said.
“We analyzed a compilation of plate tectonics models of Tethyan ocean evolution and thermal history models with features of deep precipitation and mantle convection models.”
By combining these datasets, the team was able to reconstruct a previously hidden chapter of Earth’s geological history.
Applying research beyond Central Asia
Associate Professor Glory said the same research method could help scientists investigate other geological mysteries around the world. This study Nature Communication Earth and Environment.
“There are many regions on Earth where the drivers and timing of mountain building and rifting are poorly understood. Closer to home, for example, the history of Australia’s separation from Antarctica is somewhat mysterious,” he said.
“Australia drifted around 80 million years ago, but there is no obvious trace of this in the thermal history records of the Antarctic or Australian plate margins. Instead, a much older history of cooling is recorded.
“We are applying the same approach used in Central Asia to advance our understanding of the Australian-Antarctic divide.”
