and the Junction, and Yampa Mountain Upthrusts. 
Fra. 3.—Section showing the eastern end of the Uinta fold 
Mountain Upthrusts. 405 - 
Brown’s Park Group, and reach Yampa Mountain, 
which rises directly upon that axis, as does Junc- 
tion Mountain. Here we find that the descrip- 
tion that has just been given of the Junction 
Mountain upthrust will apply in all essential re- 
spects to this. All around the base of Yampa 
Mountain the strata of the Brown’s Park Group 
cover the immediate borders of this upthrust, 
even to a greater extent than they do those of 
Junction Mountain upthrust; but it is readily 
seen that the two mountains are essentially 
identical in structure and character, and that they 
have been produce ina similar manner. Yampa 
upthrust, however, is smaller than the other, and 
it is also much farther away from any other greatly 
displaced strata. Its outline is oval, the longer 
diameter, including all the strata involved,—not 
much exceeding seven miles in length,—and its 
shorter diameter is less than four miles. The 
longer diameter is nearly at right angles with that 
of Junction Mountain upthrust, and it is nearly 
transverse with the inceptive portion of the Uinta 
axis, upon which it rises. The relation of these 
two upthrusts to each other and to the main and 
inceptive portions of the Uinta fold is indicated 
by the section, Fig. 3. 
a, Yampa Mountain; b, Junction Mountain; 
c, eastern end of the Uinta Range; d, Yampa 
River, before entering Junction Mountait’s €, 
Snake River; U., Uinta Sandstone; Carb., 
Carboniferous strata; J. T., Jura-Trias; D., 
Dakota Group; Col., Colorado Group; B. Ps 
Brown’s Park Group. 
Horizontal scale: 5 miles to the inch. 
Vertical scale : 1-20 inch to 1,000 feet. 
The amount of vertical displacement is about the 
same in each c of these upthrusts, the extent of which 
given in the foregoing table) and from the contour | 
lines on the published topographic a of that 
