The Grand Canyon has a fancy East Coast pedigree, say geologists Bill Dickinson and George Gehrels of the University of Arizona. Their research explains both the origin of Arizona’s colorful gorge and the fate of the Appalachians, an eastern mountain chain that was once as mighty as the Rockies.
Most geologists believed that the rocks of the Colorado Plateau, surrounding the Grand Canyon, originated in a mountain range that ran from New Mexico to Colorado 300 million years ago. Presumably, sand eroded away from that range, then washed west and solidified into Arizona’s sedimentary rocks from 300 million to 150 million years ago.
Dickinson and Gehrels used uranium-lead dating to study hundreds of grains and match their ages with those of rocks throughout the United States and Canada. Their findings reveal a different history.
About half the sand in the Colorado Plateau originated 1.2 billion to 500 million years ago ...
