Geology of the Grand Canyon: The Cretaceous.


The platform immediately below the Pink Cliffs is picturesque rather than grand. Rough rolling ridges of yellow sandstone, long sloping hillsides and rocky promontories clad with large pines and spruces, surround the valleys. These rocks are of Cretaceous age. Upon the southward slopes of the Paunságunt and Markágunt Plateaus, they nowhere present the serried fronts of cliffs, but break down into long irregular slopes much like those of common hill countries. In those superficial and merely scenic aspects which make the terraces so impressive, the Cretaceous is for the most part notably deficient; but in those deeper studies, which are of most significance to the geologist, it holds an importance not inferior to that of any other formation. It is never wanting at its proper place in the terraces, but always displays a vast series of sandstones and clay-shales, varying from 4,000 to 5,000 feet in thickness. Around the western and southern flanks of the Markágunt, and just beneath the summit platform, they occupy a belt varying in width from 4 to 10 miles. Around the Paunságunt their relative positions and relations are quite the same. But as we pass eastward into the great amphitheater of the Paria Valley they at length take the form of cliffs of very striking aspect. The numerous ledges rise in quick succession, step by step from the valley bottom to the base of the Eocene mass of Table Cliff, which stands as a glorious Parthenon upon the summit of a vast Acropolis. The many superposed cliffs which constitute this stairway are severally of moderate dimensions, but their cumulative altitude is more than 4,000 feet, tier above tier, and their composite or multiple effect, intensified by the exceeding sharpness of the infinite details of repetitive sculpture, places it among the grander spectacles of the Plateau country. In their coloring, these cliffs are quite peculiar. There are no red, purple, orange, and chocolate hues, such as prevail in other formations, but pale yellow and light brown in the sandstones and blue-gray to dark iron-gray in the heavy belts of shale. The tones are very light and brilliant on the whole, the darker belts playing the part of a foil which augments rather than diminishes their luminosity.