44 GEOLOGY OF THE HIGH PLATEAUS. 



Plateaus are they brought to light; but around the southeastern borders of 

 the district they are displayed conspicuously. The age of these flexures is 

 apparently Post-Cretaceous and Pre-Tertiary ; that is, they occupy, in respect 

 to time, an interval which separates the Mesozoic from the Tertiary.* They 

 consist of a series of monoclinal flexures, quite perfect in form, which trend 

 from northwest to north-northwest. They involve the Mesozoic beds, but not 

 the Tertiary. They come up from the southeast, and disappear under the 

 Aquarius Plateau, and on the southern and southeastern flanks are laid bare 

 by a vast erosion. Just before they reach this plateau they are seen to 

 be eroded, and near the summit the Eocene beds are seen to lie unconform- 

 ably across the beveled edges, and still farther on near the lava cap they 

 rest upon the Jurassic. All around the southern and eastern flanks of the 

 Aquarius and along a part of the northern flank, also entirely around the 

 circumference of Thousand Lake Mountain (with the possible exception of 

 its northern end), the contact of the Tertiary with the Jurassic is obvious. 



Farther eastward in the heart of the Plateau Province, outside of the 

 district of the High Plateaus, are three more displacements of grand pro- 

 portions, of which I can make but a passing mention. The southernmost 

 is the Echo Cliff flexure, a great monoclinal seen south of the Colorado near 

 the Moquis towns. Trending a little west of north, it crosses the river at 

 the head of Marble Canon, and continuing along the Paria River dies out 

 near Paria settlement at the base of the Vermilion Cliffs. Farther east is 

 the Water-Pocket flexure, one of the grandest monoclinals of the West. It 

 crosses the Colorado in the heart of Glen Canon, and running north-north- 

 west between the Henry Mountains and Aquarius for nearly 60 miles, swings 

 around to the west in a great curve and disappears under Thousand Lake 

 Mountain. The third is the San Rafael flexure, beginning as a branch of 

 the Water-Pocket flexure, where the latter changes its trend, and running 

 north-northeast along the eastern side of the San Rafael swell, passes off into 

 the northeast and dies out again. These are all monoclinal flexures of impos- 

 ing dimensions and of perfect form. Their age I cannot speak of at present 

 in any detail, though it is hardly doubtful that they go far back in Tertiary 



' Here, as elsewhere in this work, the Laramie beds are reckoned with the Cretaceous, of which 

 they t'orni the upper group of beds. 



