404 Mountain Upthrusts. 
we also find that the formations of Paleeozoic age—which constitute 
the high mountain-peaks of the Uinta Range only a few miles away 
—are here again uplifted, not only to the surface of the low land 
around the mountain, but toa maximum height of nearly two thou- 
sand feet above it. The strata involved in this uplift—which, be- 
cause of its sharply-defined limits and of the vertical displacement 
of these strata, I have called an upthrust—occupy an elongate oval 
area, the extreme longer diameter of which is nearly twelve miles, 
and the shorter about four miles. The direction of the longer 
diameter, being in a northwestward and southeastward direction, is 
obliquely transverse to the general trend of the axis of the Uinta 
fold. In this respect, as well as by the peculiar character of dis- 
placement of the strata involved, the isolation of this upthrust is 
quite complete, although it lies so near the terminus of the main 
portion of the Uinta fold and upon the axis of its inceptive portion. 
So sharply have the strata been uplifted in this displacement that 
they are either faulted or are nearly or quite vertical at a portion of 
each side of the upthrust, and they also dip very abruptly at other 
portions and around its ends. The Mesozoic formations, through 
which the older ones were forced, lie all around the mountain, but 
immediately adjacent to it they are largely covered from view by 
the strata of the Brown’s Park Group, which lie unconformably 
upon them. The disturbance which these Mesozoic formations have 
suffered in that neighborhood beyond the base of the mountain is s0 
slight that one cannot recognize it as having been connected with the 
upthrust movement. That is, their position as marking the pres- 
ence of the inceptive portion of the Uinta fold and of certain sub- 
ordinate uplifts does not seem to have been changed by the localized 
upthrust movement. 
The Mesozoic formations,—which must have necessarily risen on 
the top of the older ones within the upthrust area,—have been 
removed by erosion, as has also a large part of the full thickness of 
the Carboniferous strata which came up beneath them. Therefore, 
only strata of Palæozoic age now enter into the structure of the 
mountain proper ; while the upturned edges of the later ones, where 
they have not been sharply severed by faulting, lie around its base. 
Going from Junction Mountain about sixteen miles along the 
axis of the inceptive fold, we pass all the way over the low lands of 
Axial Basin, the surface of which is there mostly occupied by the 
