"It flip-flopped pretty quickly," he said, adding that the study reveals these shifts can occur on a "continental scale."
New Oil Reserves?
Experts say the Amazon drainage assumed its present west-to-east flow at least 16 million years ago.
"The Amazon fan right now is an active oil and gas exploration area," Coleman said. "And if things were flowing in the other direction, then it makes sense to look where the ancient Amazon fan was being deposited for those sorts of natural resources."
Any potential reserves would lie in the central Amazon Basin of Brazil and off the west coast of South America.
The study's findings highlight that "the surface of the Earth is very transient," study co-author Russell Mapes, a UNC graduate student, said in a press statement.
"Although the Amazon seems permanent and unchanging, it has actually gone through three different stages of drainage since the mid-Cretaceous,"—about a hundred million years ago—"a short period of time geologically speaking."
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