London: The rise of one of the highest and flattest places on the planet – the Tibetan Plateau, in China’s Sichuan province, began much earlier than thought, a new study has suggested.
According to an international team of geologists, the Indian tectonic plate began its collision with Asia between 55 and 50 million years ago, but “significant topographic relief existed adjacent to the Sichuan Basin prior to the Indo-Asian collision.”
“Most researchers have thought that high topography in eastern Tibet developed during the past 10 to 15 million years, as deep crust beneath the central Tibetan Plateau flowed to the plateau margin, thickening the Earth’s crust in this area and causing surface uplift,” Eric Kirby, associate professor of geoscience, Penn State, said.
“Our study suggests that high topography began to develop as early as 30 million years ago, and perhaps was present even earlier.
Kirby and his team looked at samples taken from the hanging wall of the Yingxiu-Beichuan fault, the primary fault responsible for the 2008, Wenchuan earthquake.
The researchers used a variety of methods including the decay rate of uranium and thorium, helium in the minerals apatite and zircon. They also used the fission track dating, an analysis of tracks or trails left by decaying uranium in minerals in apatite and zircon.
“The results show that the rocks cooled relatively slowly during the early and mid-Cenozoic -- from 30 to 50 million years ago -- an indication that topography in the region was undergoing erosion.
The findings also suggest that this gradual cooling was followed by two episodes of rapid erosion, one began 30 to 25 million years ago, while other dates back to 15 to 10 million years and is continuing even today.
“We are still a long way from completely understanding when and how high topography in Asia developed in response to India-Asia collision,” Kirby claimed.
“However, these results lend support to the idea that much of what we see today in the mountains of China may have developed earlier than we previously thought,” he added.
This study has been published in the Nature Geoscience.
First Published: Friday, August 17, 2012, 19:16