CHAPTER V
THE CENOZOIC ERA
Although chapter five is the most recent in the earth’s history and lasts up to the present day, evidences of its life and its happenings are extremely meager in the Grand Canyon region. With the exceptions of the fresh water deposits formed during the very early part (Bryce Canyon formations) and of the many volcanoes built in the later stages, no rocks were formed here during that chapter. This region was then above sea level and erosion was working continuously. The great level plain which today forms the plateau surface at Grand Canyon was created by the wearing away of overlying rocks. The Grand Canyon itself and also Zion and Bryce Canyons were sculptured. In fact, all of the features of erosion which today make this desert region so picturesque and fanciful owe their origin to the various agents of erosion which have been at work during this most recent chapter of the world’s history.
The “Age of Mammals” is a name often applied to the last era. Creatures not unlike some of the most advanced forms of life found today lived even in the early parts of this age. As the era progressed, nevertheless, a development was noticeable until finally in the very last part man himself appeared. Though few remains of this interesting and comparatively recent life have been found in northern Arizona and southern Utah, still a few elephant tusks, some camel teeth and the more recent remains of early cliff and pueblo dwellers give evidence of a thrilling history during parts of this era.
In the following pages will be found brief sketches of some of these interesting features represented in the Grand Canyon region. The many activities of erosion such as canyon-forming, the eruption of volcanoes, influences of the great ice sheets of the north, crustal movements, fragmentary evidences of early mammals, and lastly early man himself are all introduced.
BRYCE CANYON FORMATION
(WASATCH: EOCENE EPOCH)
The formation found at Bryce Canyon and at Cedar Breaks in southern Utah has the distinction of being composed of the most recently formed sedimentary rocks in this plateau region. It was during the early part of the last great chapter of history that lime and some sand were accumulating here in fresh water. They are believed by most geologists to represent the deposits of ancient lakes and in them are found freshwater mollusks. Rivers and other agents of deposition probably also took a part in the forming of these strata as is indicated by the great irregularity and variety of sand and other sediments. Truly the origin of these rocks presents an interesting problem.
BRYCE CANYON AERIAL PHOTO COPYRIGHT FRED HARVEY
MAP OF THE COLORADO RIVER