The Nature paper proposes that the proto- Colorado River first flowed from the Little Colorado River valley through a pre-existing East Kaibab paleocanyon and began to carve Grand Canyon about 6 million years ago; Ma= million years; photo by Ted Grussing.
that also hosted beavers, leopards, and rhinoceroses, all surrounded by semi-arid scrublands; their descendants are the Colorado River pikeminnow and chub; fish fossil picture from Jon Spencer; stratigraphic drawing of Whitecone Peak from Shoemaker et al., 1957.
was also heralded by the appearance of 60-40 Ma detrital sanidine grains in far-traveled Colorado River sand deposits of the Bouse Formation; Ma= million years; photo by Laura Crossey.
Photo credit: Ted Grussing
