244 GEOLOGY OF THE HIGH PLATEAUS. 



As we enter the lower gateway of the gorge ascending from Sevier 

 Valley we at once recognize tlie nature of the displacements which have 

 occurred. On the north side are seen immense beds of volcanic conglom- 

 erate dipping at angles varying from 12° to 25° to the westward. There 

 is much repetitive faulting here. Again and again the beds have sheared 



Fig. 4. — Faults at lower end of East Fork Canon. 



and slipped, the throws varying from 200 to 350 feet, all of them being 

 thrown to the eastward. More than 2,000 feet of conglomerate, beautifully 

 stratified in huge massy layers, with intercalations of dark liornblendic 

 trachyte of the roughest description, are exposed in this part of the gorge. 

 Suddenly we miss the conglomerates. They appear to end abruptly at a 

 lateral ravine which enters the main canon from the north, and on the 

 opposite side of the ravine the I'ocks are of a totally diiferent character. 

 Through that ravine runs the main throw of the great Sevier fault, here of 

 about 2,500 feet of displacement. As we look bej^ond it and up to the tow- 

 ering crags of the principal plateau mass, we again recognize the continua- 

 tions of the conglomerates in the palisjjides bounding the tabular summit. 

 Beneath them another series of strata has been brought to light by the lift 

 of the fault and the erosion of the canon. These are tufaceous deposits, 

 presenting features of great interest. 



The general aspect of these beds is shown in Heliotypes V and VI.* 

 It is obvious at once from their very aspect that they are water-laid, yet 

 when closely examined all of them are seen to have been subject to altera- 

 tion in varying degree, which gives them the appearance of massive volcanic 

 rocks. There is one member about 120 feet in thickness which has the 

 character of a volcanic rock so pronounced that no person would doubt that 



" The summit of tlio plateau is uot visible from the points where the photographs were taken, as 

 the upper -walls of the cailou are beyond the summits of the lower walls. 



