'Tibetan Plateau was larger than previously believed 40m years ago'

Geologists have determined that the Tibetan Plateau-the world's largest, highest, and flattest plateau-had a larger initial extent than was previously documented.

Gregory Hoke, assistant professor of Earth sciences, said they've determined the elevation history of the southeast margin of the Tibetan Plateau, asserting by the Eocene epoch (approximately 40 million years ago), the southern part of the plateau extended some 600 miles more to the east than previously documented. This discovery upends a popular model for plateau formation.

Known as the "Roof of the World," the Tibetan Plateau covers more than 970,000 square miles in Asia and India and reaches heights of over 15,000 feet.

He said that the tectonic and topographic evolution of the southeast margin has been the subject of considerable controversy, asserting that their study provides the first quantitative estimate of the past elevation of the eastern portions of the plateau.

Hoke said surface uplift, caused by lower crustal flow, doesn't explain the evolution of regional river networks, referring to the process by which a river drainage system is diverted, or captured, from its own bed into that of a neighboring bed.

He said that their study suggests that river capture and drainage reorganization must have been the result of a slip on the major faults bounding the southeast plateau margin.

Hoke's discovery not only makes the plateau larger than previously thought, but also suggests that some of the topography is millions of years younger.

He 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.

The study has been published in the journal Earth and Planetary Science Letters.