HAVASU FALLS IN REDWALL LIMESTONE. GRAND CANYON
Large amphitheaters, many curving alcoves, caves, and solution tunnels are all characteristic features of the great Redwall. It is composed of relatively pure lime so rain and other waters have a chemical action upon it—they leach and dissolve it. Waters all tend to drain toward curving centers, and so increase this curving. Everywhere the rounding off of corners takes place.
The origin of the Redwall Limestone is as interesting as its form. The purity of the lime indicates that it was built up in a relatively wide and quiet sea. Its composition represents a vast accumulation of the skeletons of ancient plants and animals. Seashells are found in great numbers, some of them preserved in delicate detail. These and other forms of ocean life clearly indicate that a great sea connection then existed between this region and that of western Canada to the north.
TRACKS IN THE SUPAI SANDSTONE
(PERMIAN PERIOD)
During that period in geological history known as the Permian, when some of the beds of soft coal in eastern America were being formed, a large area in northern Arizona was receiving red sediments from the east, probably carried by rivers from the granitic highlands of that region. Today these sediments appear in the Grand Canyon walls as alternating layers of red sandstone and shale immediately above the great Redwall. They are almost a thousand feet in thickness.
TRACKS OF SHORT-LEGGED PREHISTORIC ANIMAL. SUPAI FORMATION. GRAND CANYON
When the red beds were accumulating in this region, the climate probably was more or less arid; the vegetation consisted principally of ferns and other lowly plants; and the animal life included a group of large but primitive four-footed creatures. Numerous tracks of the latter, preserved in the walls of Grand Canyon, have provided one of the most interesting discoveries of recent years. Some of these footprints are several inches in length, and the number of toes varies between three and five. They show no close relationship to the tracks of other localities, and apparently represent a fauna new to North America.
LANDSCAPES OF THE HERMIT SHALE
(PERMIAN PERIOD)
