Uranium Dating Puts Grand Canyon Carving at 6 to 5 Million Years Ago

3 articles · Updated · Earth.com · Aug 17

A 2026 Science study says the Grand Canyon’s main cutting began between 6 and 5 million years ago, much later than the 1.75-billion-year age of the basement rock it exposes.
19 sandstone samples from Arizona’s Bidahochi Basin yielded zircon grains that match early Colorado River sediment downstream, placing river water east of the canyon by 6.6 million years ago.
That signal coincided with faster deposition, a strontium-isotope shift and fossils of large fast-water fish, pointing to a river feeding Hopi Lake until it spilled over the Kaibab uplift and drained westward.
The spillover model fills a key gap between evidence that the Colorado River existed in western Colorado by 11 million years ago and had exited the western canyon by 5.6 million years ago.
The finding does not end the debate: some researchers have argued parts of the canyon were near modern depth 70 million years ago, while a 2014 synthesis proposed younger carving linked older paleocanyons into one system.