DISPLACEMENT. 177 



hence the summit of the Point of Rocks Group was earned about as high 

 in the western as in the eastern region. 



O 



From the axis on either side the beds are flexed in a gentle curve to 

 the north and south for many miles until the flanks of the range are reached, 

 where the beds are seen to drop down by abrupt flexures or faults, and 

 these lines of maximum displacement are subparallel with the axis. Thus 

 a great block having its longest axis in an easterly and westerly direction 

 was uplifted. In some places this block was severed from the adjacent 

 country by fracture; in some places by more or less abrupt flexure; and it 

 was itself flexed gently from the axis either way. Nothing more is needed 

 to explain the character of this uplift between the lines of maximum dis- 

 placement, but the latter present many interesting facts. 



On Plate III, this portion of the Uinta uplift, together with the dis- 

 placements of the Yampa district are represented in a stereogram. The 

 general axis of the great uplift is easily recognizable, as is also the gentle 

 flexure in either direction from this axis. Then the great Uinta fault h, h, 

 h, h is seen on the north with the Flaming Gorge branch i, i. On the south 

 side of the Uinta Mountains in the Island Park district we find the north 

 Ti-ra-kav flexure />*, k, k and the south Ti-ra-kav flexure /, /, L In the 

 Yampa district on its northern border the eastern extension of the north 

 Ti-ra-kav flexure is scarcely seen, as there is an oblique area of upheaval 

 between the Island Park sag d, d and the Echo Park sag e. The flexure of 

 the Echo Park sag also becomes less abrupt in an easterly direction until it 

 almost fades out. The displacements south of the'Island Park and Echo 

 Park sags need no further mention here, as they will be discussed in a sub- 

 sequent portion of this chapter. 



It will be seen in the Island Park district on the south side of the 

 Uinta uplift that there are two lines of maximum downthrow approxi- 

 mately parallel, the north and south Ti-ra-kav flexures ; the beds between 

 these two flexures are nowhere horizontal. The south Ti-ra-kav flexure 

 disappears toward the west until the region embraced in the stereogram is 

 passed ; a little farther westward it re-appears, sometimes as a flexure but 

 usually as a fault. Passing the oblique uplift between the Island Park and 



*Echo Park sags we again have two lines of maximum downthrow. The 

 12 p G 



