260 GEOLOGICAL SURVEY OF THE TEERITOEIES. 



ite, d, similar to that of White Eock Mountaiu. Its direction as it 

 crosses tlie creek is northwest and southeast. It is the south extension 

 of an island-like area of granite like that of White Eock and Italia. 

 Snow-Mass Mountain and Capitol Peak are two of the principal high 

 points in this area. On the northeastern side of 'this belt (at e in the 

 illustration) the Silurian beds are seen resting on the granite, and above 

 are the Carboniferous and Triassic formations. Here there is a turn in 

 the course of the creek. Above the granite belt it follows the strike of 

 the sedimentary rocks. It is this part of its course that is parallel to 

 the main stream, from which it is separated by two ridges, c and/. Fig. 

 2, Plate XVIII. The first one, /, is composed mainly of red sandstones 

 and conglomerates, probably of Permo-carboniferous age, or possibly in 

 part Triassic. Section 27 was made on the western side of the second 

 ridge, (c in the illustration.) The creek rises in an amphitheater between 

 Station E, or Maroon Mountain, and another high point of similar for- 

 mation. On the eastern side of the valley is a high bluff-like wall com- 

 posed of red sandstones and conglomerates, the latter prevailing toward 

 the base of the cliff. The general dip is toward the northeast, at an 

 angle of about 20°. There is also a, slight curve on the face of the wall 

 along the strike of the beds. As we go toward Maroon Mountain the 

 bright red sandstones become darker. Maroon Mountain derives its name 

 from the color of its rocks. We did not ascend it, but made a station on 

 a high point a short distance south of it. Here the rocks are mostly 

 sandstones and conglomerates, a thin bed of gray limestone now and then 

 appearing toward the base of the station. The sandstones are intersected 

 by numerous dikes, which are probably connected with the main mass 

 of granite. This may account for the changes in color and structure that 

 we notice in the sandstones. All the dikes are irregular. A prominent 

 one intersects Maroon Mountain, and another the ridge that rises toward 

 it. East of Maroon Mountain is a dike, which is probably the southern 

 extension of the large dike seen east of Snow-Mass Mountain, and to 

 which I shall refer again. It is only near the base of Station 76 that 

 we find any limestone. On the summit the beds are brownish, becoming 

 red as we go down. These beds are also, for the most part, finer grained. 

 In some places there are circular spots resembling sections of concretions. 

 They are generally white or light yellow, and sometimes have a black 

 central point. IS'ear the base of the hill are'also greenish shales. The 

 beds exposed along the creek at the bottom of the caiion are probably 

 of Carboniferous age, while those on the summit of the ridge should 

 perhaps be referred to the Triassic. On the southwest face of White 

 House, or Suow-Mass Mountain, a small branch of Eock Creek rises. 

 It soon expands into a beautiful lake, to which the name of Elk Lake 

 has been given. A short distance below the lake, the creek falls over 

 the edges of the stratified rocks to the level of the main creek, a vertical 

 distance of 1,102 feet. It fails over these rocks in two falls or cascades, 

 the white foaming belt of water contrasting with the bright-red con- 

 glomerates and sandstones. Snow Mass Peak is 13,785 feet in height, 

 and is made up of a light-colored granite, such as we saw on White 

 Eock and on Italia. Southwest of the peak, at the, head of the creek 

 flowing into Elk Lake, there seems to be a dike in the granite. First 

 is a band of very fine-grained dark rock, with seams of white feldspar. 

 It is about 100 feet in thickness, and its direction is about due north- 

 west and southeast. Just below it is a band about 3 feet thick, of a 

 green rock, the color of whicli is probably due to iron. This is prob- 

 ably dioritic. Next to it is about 4 feet of the same rock that we saw first. 

 It is followed by about 50 feet of a porphyritic rock, with a green matrix 



