PEALE.] GEOLOGY FEYING-PAN CREEK VALLEY. 265 



below the butte. Beyond tbe Cretaceous beds on the east side of the 

 river, which are, I think, at this place right side up, there are ex- 

 posures of red-beds, which I did not have time to visit. About eleven 

 miles farther down stream, Snow Mass Creek comes into Eoaring Fork 

 from the southwest. This creek has two large branches, one of which 

 heads near Maroon Mountain and Snow Mass Mountain, while the other, 

 Capitol Creek, rises north of the Capitol. Opposite the mouth of the 

 creek there is a hill capped with a volcanic rock, which is also exposed 

 on the southwest side. It seems to be trachytic in character. A simi- 

 lar hill stands near the mouth of Frying-Pan Creek on the north side. 

 South and southwest of Eoaring Fork is a large area reaching from the 

 river to the Elk Mountains, covered with Cretaceous rocks. Fig. 2, 

 Plate XIX, represents a section across this area. At the point a the 

 dip is south or a little east of south ; angle of inclination about 15°. 

 At the base of the hill h, on the creek coming from Sopris Peak, ex- 

 posed on the left side, is a sandstone which I took to be Cretaceous No. 

 1, (Dakota group,) above which were limestones and shales, all dipping 

 west of north at an angle of about 20°. There is, therefore, at this 

 place a synclinal fold, the axis of which is northeast and southwest. 

 At the point c there is a second fold parallel to the first. The Cretaceous 

 area extends across Eoaring Fork, and also westward around the end of 

 Sopris Peak, and across Eock Creek. Opposite the mouth of Eock 

 Creek, on the east side of Eoaring Fork, there is an outcrop of red-beds 

 below the Cretaceous. I think the section between Frying-Pan Creek 

 and this i)oint is as represented in Fig. 3, Plate XX. Sopris Creek, 

 seen from a distance, has a rounded outline. It is composed of erup- 

 tive granite, and is the center of the third eruptive island in the Elk 

 Mountains. On the southeast side we have chloritic schists, quartzites, 

 and sandstones, all very much metamorphosed. These beds have a dip 

 toward the Capitol. In them I found the following minerals : Eematite, 

 actinolite, chlorite^ and talc. The peak is 12,240 feet in height. Between 

 the Capitol and Sopris we have a fold as represented in Fig. 1, Plate XX, the 

 center being filled with red-beds that, I take it, belong to the Triassic. 

 There is not only a fold in this direction, but also east and west, as shown 

 in Fig. 2, Plate XX, which represents a section through the range at right 

 angles to the section in Fig. — . To the westward the only rocks to be seen 

 are Cretaceous. To the north and northwest we have the valley of Eoar- 

 ing Fork extending -to the Grand. West of the mouth of Eock Creek 

 there are some comparatively low hills in which there are exposures of 

 red-beds, as seen from the summit of Sopris. Leaving Sopris Peak, we 

 followed Frying-Pan Creek to its head. We had considerable difficulty 

 getting up the creek, as it is in caiion the greater part of the way. The 

 rocks exposed at the lower part are all red sandstones, dipping a few de- 

 grees east of north, inclining from 7° to 10°. About ten miles from 

 the mouth of the creek we reached an open valley, in which we camped. 

 Here, on the northern side of the valley, there were some very fine cas- 

 tellated forms in the red sandstones. These beds dip a little east of 

 north, but as we go north the dip changes toward the south. A short 

 distance above the camp the creek is again in caiion, and here we find 

 the dip of the red-beds is west. This changes to southwest as we fol- 

 low the outcrop. Where the beds cross the creek we have a deep nar- 

 row caiion cut through them at right angles to the strike. The dip of 

 the beds is south 00° west, and the angle 30° to 50°. The outcrop 

 forms a high ridge about 950 feet above the level of the valley just 

 above. This valley is comparatively wide, and the stream flows through 



