50 GEOLOGICAL SURVEY OF THE TERRITORIES. 



valleys cut at right angles. Each ridge contains a massive bed of 

 quartzite, which in some cases rises to a great height, and between the 

 alternate ridges is a thin series of slates and sandstones, which, yielding 

 more readily to the atmospheric agents, have been worn away, form- 

 ing a narrow depression or pass from one valley to the other. 



At the head of the streams the rocks that form the divide seem to 

 have been elevated in a horizontal position, and they exhibit the most 

 remarkable architectural forms as cones, pyramids, castles, cathedrals, 

 &c. The strata are clearly shown, and are perfectly horizontal in most 

 cases, sometimes inclining slightly to the southwest. Is! o where else in 

 the West have I ever seen rocks assuming these peculiar forms. The 

 scenery has an artificial appearance, so uniformly regular is the shape of 

 some of the pyramids. These rocks most effectually shut off all water 

 communication between the north and south side of the Uinta range. 

 The distance from the red-beds or triassic, including the carboniferous 

 limestones, to the crest of the mountains, I estimated at five miles in a 

 straight line, and the inclination varies from 40° to 75°. In all this 

 series of strata, from the red-beds to the oldest quartzites, I was able to 

 detect no unconformability. The connection of the sandstones with 

 the carboniferous limestones was perfect, so far as could be ascertained 

 by the eye, whatever may have been the chasm in time. Not a trace of 

 a fossil was found below the limestones, although I strongly suspect the 

 purplish sandstones to be of Lower Silurian age. The texture of the 

 upper beds of sandstone is so much like the Potsdam sandstones, as 

 may be observed in other portions of the Eocky Mountain region, I was 

 lead to suspect that the upper portion might be Lower Silurian. The sec- 

 tion along the valley of Black's Fork is clear, inasmuch as the rocks are 

 cut through at right angles to the strata and they all present an unbroken 

 series from the oldest quartzites exposed to the carboniferous limestones ; 

 and close to the oldest quartzites are thin beds of sandstone, apparently 

 unchanged or only partially so, and resembling in texture and color the 

 upper sandstones, which I am inclined to regard as Silurian. I have 

 estimated the entire thickness of stratified rocks exposed here at ten 

 thousand feet. If this is true, about eight thousand feet consist of the 

 sandstones and quartzites rising to an elevation of over twelve thousand 

 feet above tide- water. 



I am inclined to believe that the upper beds are Silurian, that they 

 pass gradually down without any break in the sequence of time to 

 rocks of Huronian age. The purplish quartzites are almost precisely 

 like those which occur at the Sioux Falls in Dakota, and at the Pipe- 

 stone quarry, in color and texture, which Professor Hall . regards as 

 Huronian age. At any rate, I have never observed such a series of 

 rocks in any other portion of the West, and am inclined to think they 

 are confined to the Uinta range. The Uinta Mountains are not far 

 from the Wasatch range, and apparently join on to that range; yet I 

 have passed through the Wasatch range at right angles at different 

 points, and was able to discover no such series of strata. The precise 

 or approximate age of these rocks is a very interesting problem to me, 

 and I regret that my time will not permit me to make a more thorough 

 examination of the range. A careful study of the southern slope, and 

 the intermediate country southward into the Uinta basin, might afford 

 some clue to their age, but I suspect that there are no fossiliferous strata 

 in the series. 



As I have before stated, two of the main branches of Black's Fork 

 and Bear Biver take their rise in the axis of elevation at precisely the 

 same point, run parallel for about five or six miles and then diverge, the 



