The world's largest river basin, the Amazon, once flowed from the Atlantic Ocean to the Pacific - opposite its present direction - according to research by a geology graduate student and his advisor at the University of North Carolina at Chapel Hill.
Russell Mapes, a graduate student from Grass Valley, Calif., set out in 2004 to study the speed at which sediment in the Amazon travels from the Andes mountains, in the present headwaters of the river, to the Atlantic. While studying sedimentary rocks in the river basin he discovered something else - ancient mineral grains in the central part of South America that could only have originated in now-eroded mountains in the eastern part of the continent.
Of course, they're talking pre-Cretaceous. . . . .