178 STRUCTURAL GEOLOGY. 



more northern, which is a continuation of the northern Ti-ra-kav flexure, i# 

 but faintly seen in the stereogram ; the southern, which is the flexure of the 

 Island Park sag, is more pronounced. All of these maximum flexures on 

 the south side appear to be but slight from an examination of the stereo- 

 gram, as its scale is very small and no exaggeration has been permitted ; 

 but they are very important characteristics in the structural geology of the 

 region, and give rise to very remarkable topographic features. In the 

 broad generalization necessitated by the scale of the illustration many 

 minute displacements, parallel, oblique and transverse to these larger, dis- 

 appear ; that is, in the production of these greater flexures the beds were 

 locally contorted and broken. 



Turning now to the north side of the Uinta uplift, we find that the line 

 of maximum displacement, beginning at the eastern extremity, is at first a 

 gentle flexure with comparatively small uplift; but the flexure rapidly 

 increases in abruptness and magnitude until at last we find that the beds are 

 broken and we have a fault ; but only a portion of the uplift is by faulting, 

 and the beds on the thrown side are turned up at the edge. Farther west- 

 ward the beds below lie nearly horizontal, and the beds on the upheaved 

 side are flexed downward; and these conditions alternate so that we some- 

 times have the upheaved beds flexed downward only, while the thrown beds 

 are nearly or quite horizontal. Again, we have the upheaved beds nearly 

 horizontal at the edge and the thrown beds decidedly flexed upward; and 

 another variation is found where the upheaved beds are flexed downward 

 and the thrown beds upward. 



It is probable that the displacement began by flexure, and continued 

 until much of it was made in this way, and finally the beds broke, and the 

 latter part of the displacement was by faulting. And when this faulting 

 occurred, in some places the beds broke on the side of the flexure nearer the 

 axis, in other places on the side of the flexure farther from the axis, and in 

 still other places between the sides of the flexure ; that is, the line of fracture 

 meanders along the zone of flexure. As we approach the Flaming Gorge 

 district we find that the faulting is greatly diminished, while the flexing is 

 increased, the total throw or uplift, as we may please to consider it, remaining 

 approximately the same. At last this line of abrupt displacement branches, 



