. 406 Mountain Upthrusts. 
region. The contour line which cuts the top of the Uinta Sandstone in 
both these mountains passes along the southern side of Axial Basin, 
approximately at the base of the Laramie and the top of the Fox 
Hills Group. Referring to the preceding table, we find the thick- 
ness of the intervening formations to be eleven thousand eight hun- 
dred feet. It is therefore plain that the amount of vertical dis- 
placement in both these mountains is not less than is represented by 
those figures. That is, within the narrow and sharply defined 
limits that have been described, the strata of which both these 
mountains are composed have been thrust up a vertical distance of 
more than two miles,—which in the case of the Yampa upthrust is 
nearly equal to one-third of the longer diameter of the area affected 
by it. 
As indicating that the amount of vertical displacement in these 
upthrusts is really greater than has been mentioned, it may be stated 
that the Fox Hills and Laramie strata referred to have themselves 
been elevated to a considerable extent in the adjacent Danforth Hills 
uplift (as shown by the section, Fig. 2). This figure will also serve 
to illustrate the relation of the Yampa upthrust to the inceptive fold 
and to the adjacent Danforth Hills uplift. That is, if within the 
space indicated by the length of the line xx the strata should be 
elevated until the base of the Carboniferous series reaches the place 
of the uppermost dotted line, the vertical extent and lateral restriction 
of the Yampa upthrust will be indicated. i 
- It is true that the vertical displacement in the case of these two 
upthrusts is much less in amount than is that of the great fold ; 
but the amount of displacement is far more remarkable in the case 
of the upthrusts than it is in the case of the fold, because of the very 
narrow limits within which the displacements in the former case 
have taken place. The narrow and sharply defined limits of these 
upthrusts, and the severing of the displaced portions of the forma- 
tions from the great mass of each respectively, with little or no gen- 
eral disturbance of the latter beyond those limits, may be comp 
to the action of a large punch on being forced by great power through 
a number of thick iron plates. The comparison will be more com- 
plete if we conceive that the cutting-border of such a punch had 
become dulled at certain places, so that a part of the iron through 
which it was being forced would drag and not be sharply severed. 
Portions of the uplifted strata at the base of both these mountains 
