210 GEOLOGY OP THE HIGH PLATEAUS. 



once extended over the vast expanse before us and far beyond the limits 

 of vision to the south- and southeast. One after another they have been 

 swept away by the ordinary process of erosion, and the great expanse 

 of desert around the Colorado has been denuded down to the Carbonifer- 

 ous. Here and there an insulated patch of the Trias remains, fading 

 remnants of formations which were once continuous and without a break; 

 but the whole of the vast Cretaceous system and the heavy Eocene beds 

 have not left a single butte upon the denuded portion. Sixty to eighty 

 miles to the east of us the Cretaceous still extends uninterruptedly from 

 the southern slope of the Aquarius Plateau to the Colorado and thence 

 into Arizona. A little farther westward and the Upper Trias similarly 

 stretches across the interval. But from the eastern wall of the Kaibab to 

 the mouth of the Grand Canon the Carboniferous forms the floor of the 

 country, and no later beds are found within 50 miles of the river except a 

 few outliers of the Shinarump. 



