The study, to be published Friday in journal Science, said an analysis of mineral grains from the bottom of the western Grand Canyon indicates that it was largely carved out by about 70 million years ago -- a time when dinosaurs were around and may have even peeked over the rim.
Researchers used a dating method that exploits the radioactive decay of uranium and thorium atoms to helium atoms in a phosphate mineral known as apatite. The helium atoms were locked in the mineral grains as they cooled and moved closer to the surface during the carving of the Grand Canyon.
Temperature variations at shallow levels beneath the Earth's surface are influenced by topography, and the thermal history recorded by the apatite grains allowed the researchers to infer how much time had passed since there was significant natural excavation of the Grand Canyon.
"Our research implies that the Grand Canyon was directly carved to within a few hundred meters of its modern depth by about 70 million years ago," said CU-Boulder Assistant Professor Rebecca Flowers in a statement. (*/T007)
Editor : Nyoman Budhiana
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