Beijing: Yangtze - the world`s third longest river - located in China, is at least 23 million years old, an international team of scientists has found.
The study conducted by a combined team of Chinese, Japanese, American and Australian researchers has found that Yangtze is at least 23 million years old but no older than 36.5 million years.
The river flows from the mountainous glaciers of the Tibetan plateau 6,418 km across China to the East China Sea at Shanghai.
Yangtze has a long and varied history, going back thousands of years but until now, scientists have not been able to determine just how long the river has been in existence.
In the new study published in the Proceedings of the National Academy of Sciences, researchers studied Lower Miocene sediments and compared them with sediments that came about in modern times.
They found virtually no differences between the two which the teams suggested, means that a river very much like the one that exists today, existed as far back as 23 million years ago.
Most research to date has suggested that the river changed direction during an uplifting of the Tibetan Plateau following an India-Eurasian plate collision millions of years ago.
Still, estimates of the river`s age have varied from 45 million years ago, to just 2 million years ago.
To get a better estimate, the new research studied rocks taken from the Jianghan Basin, downstream from the Three Gorges Dam, news website `Phys.Org` reported.
The rocks there were virtually indistinguishable from rocks found in the modern era, and because such rocks can only form in the presence of moving water.
The researchers concluded that the river must have existed in close to its present state, approximately 23 million years ago - the age of the rocks they examined.
And because no such rocks could be found that were dated older than 36.5 million years, the researchers used that number to estimate the earliest possible date of formation of the river.
The researchers noted that their estimation of the age of the river coincides with both the Tibetan Plateau uplifting timeframe and a permanent increase in summer monsoon rains, which would of course have fed more water to the river contributing to both its size and the path it forged to the sea.
PTI
