Instead of being shaped by the Colorado River 5 or 6 million years ago, a new analysis of the minerals in the 280-mile (450-km) gorge suggests it was formed by a much older river likely frequented by the dinosaurs that roamed North America some 70 million years ago.

The research, published in the journal Science, adds a new component to 150 years of wrangling over the exact age of the mile-deep canyon in Arizona, according to University of Colorado Assistant Professor Rebecca Flowers.

A new method of measuring radioactive decay from minerals in the soil suggests the gorge is 70 million years old, Flowers, who worked with Professor Kenneth Farley of the California Institute of Technology one of the project, said in a telephone interview.

The team examined soil samples from both the western and eastern parts of the canyon, and their findings confirmed a similar study published last year based on a study of just one side of the canyon.

It suggests that the canyon would have been carved by a river that existed before dinosaurs became extinct 65 million years ago and before the existence of the modern Colorado River system, a 1,450-mile-long (2,333-km-long) body of water that flows from Colorado to Mexico.

"At that time, the topography of the landscape in the Western U.S. looked very, very different than today," she said.

In fact, the elevation of the land in the West was higher and that ancient river would have flowed in the opposite direction of the Colorado River, she said. (Reporting By Caroline Humer; Editing by Julie Steenhuysen and Cynthia Osterman)

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