BIOSTRATIGRAPHY OF THE GRAND CANYON
"The Grand Canyon contains a marvelous record of geologic and
paleontologic events spanning most of the last two billion years, nearly
one half of the life span of this planet. Although it is neither the
deepest nor the longest canyon in the world, it is one of the fewest
places where so many chapters of earth history are clearly displayed."
Stanley A. Beus & Michael Morales
Grand Canyon Geology