Early Tibetan Plateau was larger than previously thought

The Tibetan Plateau - the world's largest, highest, and flattest plateau - may have extended almost 1,000 kms more to the east, around 40 million years ago, than previously documented, scientists say.
Known as the "Roof of the World," the Tibetan Plateau covers more than 2,512,288 square kms in Asia and India and reaches heights of over 15,000 feet.
Researchers have now found that approximately 40 million years ago, the southern part of the plateau extended some 965 kms more to the east than previously documented.
"We've determined the elevation history of the southeast margin of the Tibetan Plateau," said Gregory Hoke, assistant professor of Earth sciences at Syracuse University in the US.

"By the Eocene epoch (approximately 40 million years ago), the southern part of the plateau extended some 600 miles (965 kms) more to the east than previously documented. This discovery upends a popular model for plateau formation," Hoke said.
Hoke was attracted to the topography of the plateau's southeast margin because it presented an opportunity to use information from minerals formed at the Earth's surface to infer what happened below them in the crust, 'phys.Org' reported.

"The tectonic and topographic evolution of the southeast margin has been the subject of considerable controversy. Our study provides the first quantitative estimate of the past elevation of the eastern portions of the plateau," he said.

Historically, geologists have thought that lower crustal flow - a process by which hot, ductile rock material flows from high- to low-pressure zones - helped elevate parts of the plateau about 20 million years ago.
But years of studying rock and water samples from the plateau have led Hoke to rethink the area's history.
His data indicates that the plateau has been at or near its present elevation since the Eocene epoch. Moreover, surface uplift in the southernmost part of the plateau - in and around southern China and northern Vietnam - has been historically small.
Hoke's discovery also suggests that some of the topography is millions of years younger.

"Our data provides the first direct documentation of the magnitude and geographic extent of elevation change on the southeast margin of the Tibetan Plateau, tens of millions years ago," Hoke added.
"Constraining the age, spatial extent, and magnitude of ancient topography has a profound effect on how we understand the construction of mountain ranges and high plateaus, such as those in Tibet and the Altiplano region in Bolivia," he said.
The study was published in the journal Earth and Planetary Science Letters.