pj.^i^E.] GEOLOGY SECTION NO. 26. 255 



12. Yellowish- white limestone. The upper part grades into a sandstone, 



and has small crystals of pyrites. Below the bed has an irregular 

 cross-fracture, and is white on the weathered surfaces. Thickness 

 about 20 feet. 



13. Eusty yellow quartzite with seams of eruptive rock running through 



it, which has disturbed the beds very much. The angle of the dip 

 here is about 50°, and seems to be toward the east or north of east. 

 Thickness is about 50 feet, 



14. Eruptive granite reaching to the creek, a distance of about 600 feet. 

 These beds on Teocalli Mountain seem to have been broken oft' from 



those on the west side of the creek, and carried up past them. Crossing 

 the ridge from Teocalli Creek to Dike Creek, coming from Castle Peak, 

 we followed the stream up to the foot of the peak. At the foot of Teo- 

 calli on the east side, there seems to be a dip to the west or southwest. 

 This gradually changes to the south and southeast, toward the east. 

 The exposures are all of reddish sandstones and coarse conglomerates. 

 As we go up, the strike of the sedimentary beds crosses the creek and 

 has a direction a little north of east, probably joining the line of out- 

 crop of the beds northwest of Italian Mountain. After leaving this line 

 the valley is underlaid by eruptive granite, and near the head of the 

 creek resting on this granite on the summits of the ridges on either side 

 are the sedimentary formations, forming a semicircle around the head 

 of the creek. At the head of the amphitheater thus formed is Castle 

 Peak, a high, black-looking peak, in shape somewhat resembling Teo- 

 calli. It is not so regular, however, the outline being very rough and 

 ragged. It is on the north side of the eruptive island, and is composed 

 mostly of sandstones that are very much changed and intersected with 

 dikes. We ascended the mountain, but the weather was so stormy that 

 I did not attempt to make any section. The summit is 13,930 feet above 

 sea-level, and about 2,400 feet above the head of the creek. While 

 on the top we were almost constantly surrounded by clouds, and it 

 was only occasionally and for a very short time that we were able to see 

 any of the surrounding country. From the peak eastward the general 

 strike is a little south of east, with an irregular outline until we reach the 

 head of the Gunnison River, when it turns to the north, and seemingly 

 follows a branch of Eoaring Fork, which flows to the northward. On 

 the summit is a very hard metamorphosed laminated sandstone, gener- 

 ally of a somber reddjsh-brown color, streaked in places with green. 

 Next below is a very handsome sandstone conglomerate, and then a 

 yellowish sandstone, all metamorphosed. Below these we have an alter- 

 nation of red sandstones and conglomerates until we reach the base of 

 the mountain. The beds are all more or less changed and intersected 

 by dikes, which sometimes cut across the strata, and again lie between 

 different layers. The dip is nearly due north, and the angle of inclina- 

 tion on the ridge below the summit is from 5° to 10°. It is difficult 

 without closer study to determine with exactness to what age these 

 rocks should be referred. I think it probable, however, at that the base 

 we have the Potsdam sandstone or quartzite, and above the Silurian, 

 the Carboniferous, and Permian rocks. Those on the summit are proba- 

 ably Permian. Perhaps Pernio carboniferous would be the best term to 

 apply to them. White Eock Mountain is at the head of Teocalli Creek. 

 To the south the sedimentary beds are overturned, the strike being 

 northwest and southeast and the dip to the northeast. On the north 

 the dip is to the north and northeast. To the west the sedimentary 

 beds extend across the granite. There is, however, a break, although 

 the granite does not appear through them. Before reaching this point 



