60 GEOLOGICAL SURVEY OF THE TERRITORIES. 



We passed up the valley of a small stream that flows southward from 

 Italian Peak. This peak is literally filled with dikes, which have so 

 changed the contiguous rocks that they present a great variety of struc- 

 ture and color, and hence the name. Indeed, the peak itself is the 

 result of pressure of the igneous matter from beneath. On the north- 

 east side the great mass has been pushed up 1,500 feet, so that on 

 the south side the unchanged quartzites, rusty brown and gray, stand 

 vertical, and in some instances 35*^ past a vertical. The stratified 

 quartzites are full of seams of crystalline quartz with what appears 

 to be silver ore. The upthrust of the igneous rock has produced great 

 chaos in the beds. Above this locality on the peak there is a fault in 

 which the entire group of Silurian strata is thrown off from the dike so 

 that one portion is separated from another and is lifted up vertically 

 1,000 feet above the original point of junction. In this district of igneous 

 uplifts the faults are very numerous and striking. Thrust in between 

 the strata are irregular layers of the trachyte, varying from a foot to 

 several feet in thickness, and extending horizontally sometimes several 

 hundred feet, thinning out at each end. One of these intrusions ex- 

 panded to a thickness of 40 feet on the east side of the peak. From 

 this peak we have a most remarkably extended view on every side. To 

 the south is the East Fork of the Gunnison with the red and yellow beds 

 in the foreground, and far distant the older rocks are thrown up at 

 various elevations, ai)parently local uplifts. To the west is a vast group 

 of sharp, jagged peaks and crests, saw- like, with stratified cone-shaped 

 pyramids ; some red, others dark ashen-brown, or maroon-color. All 

 the rocks, as far as the eye can reach, appear to be stratified, though 

 inclining in various directions. The general level of the summits of the 

 I)eaks is upward of 13,000 and perhaps 14,000 feet. To the east we see with 

 great distinctness the valley of Upper Gunnison with the Sawatch range 

 beyond, and on the west of the range .the ridges of stratified rocks in- 

 clining from it. These extended views from the summits of the highest 

 peaks enable us to generalize to some extent the local details that we 

 have already worked out. We see thousands of feet in thickness of 

 stratified rocks, tilted in every direction by a great number of local up- 

 thrusts of the igneous rocks, so that we see strata of different ages some- 

 times on the summits of the highest peaks, over 14,000 feet above the 

 sea. And again, in the lowest valleys we have a thick group of Silurian 

 strata, quartzites and limestones, then above them a group of Carbon- 

 iferous beds, then the red or Triassic, and in some instances the Cre- 

 taceous; but the latter are seldom seen on the high mountain-ranges. 

 As near as we could estimate, there are near this peak 2,000 feet or more 

 of Silurian quartzites and impure limestones ; 1,500 to 2,000 feet of lime- 

 stones and shales of Carboniferous age. 



From the Italian Peak we descended the valley of the little stream 

 that flows from its south base and runs southward into a branch of the 

 Gunnison. On the west side of the valley, or gorge, a wall of quartz- 

 ites rises up nearly vertical 2,000 feet. This valley presents an example 

 of a synclinal in which the shales are most chaotically crushed together. 

 The quartzites incline from each side of the valley or gorge. Dikes 

 of trachyte pass across the strata from east to west, sometimes disturb- 

 ing the beds so that they incline north and south, and again the dikes 

 are seen without any disturbance of the contiguous rocks. Quite abun- 

 dant fossils were found in the Carboniferous limestones ; among them 

 Atliyrus subtilita, Froductus, corals, crinoids, &c. 



As we continue toward the west the red or Triassic beds in full devel- 

 opment cover the surface as far as the eye can reach, interrupted only 



