Long after the dinosaurs were buried on the old river bar, masses of vegetable material accumulating on the margin of shallow seas were covered with sand and finally transformed by pressure into the extensive coal deposits of Carbon and Emery counties. Although no dinosaur bones have been found in this region, the sandstone above the coal beds still records the fact that no less than eight varieties of dinosaurs walked across the mud flats more than sixty million years ago. One huge beast left footprints which indicate that he took fifteen-foot strides, and another, apparently because he slipped in peaty mud, made an impression approximately four and a half feet long and two and a half feet across.
While the great reptiles were still living in some parts of the world, the region now known as Zion National Park was an arid waste or "fossil Sahara." There, sediments washed down from the mountains were blown by the wind into huge sand dunes. At the same time the desert plain was sinking gradually toward the bottom of a sea. After a long period, in which layers of limestone and shales were deposited above the sand, the area of deposition was again lifted above the water. Streams grinding down through the bedrock finally exposed the vermilion and white sandstones of Zion Canyon. The sandstone was laid down in the Mesozoic era; uplift and erosion, however, were products of a later time.
During the last period in the Mesozoic era the sea extended from the Gulf of Mexico to Alaska and from Ohio to central Utah. By the end of that period the sea had withdrawn, and lateral pressure from the west was folding the earth's crust into a system of mountains known as the ancestral Rockies. In following ages the pounding wind and rain and the abrasive action of streams reduced the ancestral mountains to a plain. By the middle of Cenozoic time the Cascade disturbance began, and vertical pressure under the present Rocky Mountain province resulted in elevation of the land and the consequent breaking and faulting of massive blocks of earth. The Cascade disturbance, together with the erosion that followed the lifting of land masses, created the Great Basin and the Rocky Mountain system, to which the Wasatch Range in Utah belongs.