HAYDEN.] 



GEOLOGY AEKANSAS VALLEY. 47 



north and east side of Buffalo Peak the unequal elevation of both, the 

 granites and the sedimentary rocks is apparent. They may be seen 

 here in contact at the base of the Peak, or near the summijb, 2,000 feet 

 above the base. Twelve-Mile Creek rises near Weston's Pass, flows 

 for a short distance, about six miles, east of south, then bends so that 

 the course is a little south of east after emerging from the range. The 

 deep gorges are very numerous, and seem to be carved out of the mass- 

 ive granites, presenting on either side remarkable sections. 



The crest of the divide at the head of the south branch of the Little 

 Platte presents a fine view of the valley of the Arkansas toward the 

 west, with the grand range of the Sawatch on the west side, like a gi- 

 gantic wall, with its wilderness of peaks, upward of 13,000, and many 

 of them over 14,000 feet. Nestled at the base of the Sawatcb, at the 

 mouth of the Lake Creek gorge, are the beautiful Twin Lakes, separated 

 from each other by a belt of morainal deposits only about 200 yards wide. 

 To the southeast may be seen distinctly the ranges about the San Luis 

 Valley, with Ouray and Uncompahgre Peaks rising far above all the 

 rest. To the east we have the South Park full in the foreground, look- 

 ing like an immense meadow. The ridges which run across it in differ- 

 ent directions are softened down by the distance. Pike's Peak, with the 

 ranges of mountains on either side, shuts off" the vision from the broad . 

 I)lains beyond ; it rises so far above the rest that it becomes a most 

 important landmark for a radius of fifty to eighty miles in every direc- 

 tion. To the northeast and west is the splendid group of peaks of 

 which Mount Lincoln is the crowning one ; while to the northwest are 

 the sources of the Arkansas with the Tennessee Pass and its associated 

 ranges of mountains. The Blue Eiver range can be seen dimly beyond. 

 Such are the geographical features of this remarkable region, and I de- 

 scribe them from time to time, to convey to the reader the fact that the 

 variations are kaleidoscopic, and from every important mountain-peak 

 a fresh and equally grand view may be obtained. 



As I have before stated, it is my belief that the range of mountains 

 on the west side of the South Park is a portion of a grand anticlinal of 

 which the Sawatch range is the central mass or axis. Therefore the 

 general inclination of the great body of the rocks of the Park range is 

 eastward, metamorphic as well as sedimentary. On the east side of the 

 crest the dip of the strata is obvious, and the granitoid nucleus is ex- 

 posed in comparatively few plajces, except in the gorges,, where the erod- 

 ing forces have cut deep down through the sedimentary beds into the 

 schists. But on the west side the granites are visible everywhere, 

 while the sedimentary rocks are the exception. The action of two forces 

 are indicated in this range ; one which acted uniformly and slow, ele- 

 vating the vast series of North and South ranges from the plains on the 

 east to the Colorado Eiver, and perhaps farther, and a second force 

 operating synchronously, but probably spasmodically, tossing the gran- 

 ites as well as the sedimentary group into chaos. The one acted in 

 long lines of fracture, forming regular anticlinals with the stratified 

 groups, inclining from either side of the central axis in regular order; 

 the latter bringing to the surface tlie igneous rocks, and producing those 

 wonderful faults of which we find so many illustrations in the Park 

 range. The general form of this range also reveals its anticlinal char- 

 acter, through the fragments of the sedimentary groups which have 

 broken down from the crest on the west side. In the California Gulch, 

 and to some extent in other localities, the igneous rocks have been 

 poured out over the mountain side covering both granitic and sedi- 

 mentary beds, but tlie granitic rocks predominate, and all others occur 



