PALO ALTO, Calif., Oct. 5 (UPI) — Geologists say a river as big as the modern Colorado flowed 55 million years ago in Arizona and Utah — in the opposite direction from the present-day river.
Researchers in the Department of Global Ecology at the Carnegie Institution in Palo Alto, Calif., have named this ancient northeast-flowing river the California River, after its presumed source in the Mojave region of Southern California, an institution release said Monday.
By analyzing sand grains in sedimentary deposits in Utah and southwest Arizona the researchers were able to determine that the sand at both localities came from the same source — igneous bedrock in the Mojave.
The river emptied into a large lake in Utah more than 400 miles away from the California source, scientists say.
“The river was on a very similar scale to the modern Colorado-Green River system,” Steven Davis, a postdoctoral researcher at Carnegie, says, “but it flowed in the opposite direction.”
The modern Colorado River’s headwaters are in the Rocky Mountains, flowing southeast to the river’s mouth in the Gulf of California.
The mighty California River likely met its end as the Rocky Mountains rose and the northern Colorado Plateau tilted, reversing the slope of the land surface and the direction of the river’s flow to create the present Colorado-Green River system, Davis says.
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