180 GEOLOGICAL SURVEY OF THE TEEEITOEIES. 



coal bed is forty-five degrees northeast from the base of the mountains, 

 which are not more than a quarter of a mile distant. Mr. McLaughlin in- 

 formed me that he had found "oak leaves" in the shale above the coal. 

 These beds occupy the entire north end of the park, and no older rocks are 

 seen between them and the eruptive foot-hills of the mountains. It seems, 

 therefore, that the source of the elevating forces that upheaved these 

 sedimentary formations was in the range of mountains that form the 

 western rim of the park, and, so far as I coidd ascertain, there are no 

 true ridges of upheaval on the eastern side. Exposures of erui)tive 

 rocks are seen everywhere all over the park. 



There are several localities where these rocks are thrust up through the 

 cretaceous and tertiary beds, and in the middle and southern portions of 

 tbe park are quite lofty isolated buttes and mountains of eruptive rocks. 



But one of the most conspicuous formations and greatest in extent 

 and importance is the boulder drift. This seems to be mostly confined 

 to the northern and northwestern portions of the park where the princi- 

 pal placer diggings occur. In the valley of the South Platte, especially 

 near Fairplay, there is a prodigious exhibition of the boulder formation. 

 The rocks are well rounded by attrition, and apparently have been swept 

 down from the mountains. Wherever the drift occurs, there are long 

 table lands or terraces, especially in the vicinity of the little streams, and 

 they seem to be ijlaned down with such wonderful smoothness that it must 

 have been done by the combined action of water and ice. 



Along the west and north sides of the park are a large number of lofty 

 eruptive peaks, which seem to me old volcanic cones. One of the peaks in 

 the range west of Fairplay seems to have a crater-like summit, the rim 

 broken down on the east side. All around the inside of the remainder of 

 the rim the layers of basalt appear like strata, inclining from the opening 

 in every direction as if the melted material had been poured out and had 

 flowed over the sides in regular strata. There are also tremendous 

 furrows down the sides of others. In the mountains north of the park 

 are huge depressions in these volcanic ranges, the sides of which 

 are quite red, as if they had been in active operation at a comparatively 

 modern period. I am, therefore, inclined to believe that the magnificent 

 range of mountains on the west side of the Arkansas Eiver, extending 

 far northward, is one series of old volcanic cones. As we leave the 

 l^lains and ascend the mountains at the northeast side of the park, we 

 pass immediately from the older tertiary beds, covered thickly with drift, 

 to the metamori:)hic rocks mingled with outbursts of eruptive rock. To- 

 ward the summit there was a great series of gneissic beds of all varieties 

 and textures. All these mountains east of the park have a gneissic and 

 granitic nucleus. As we descend the valley of a small branch of the 

 Srorth Fork of the South Platte from the Kenosha House, we pass down 

 a monoclinai rift. On the west side is the slope covered with a thick 

 growth of pine and spruce, while on the left side are the projecting edges 

 • of the massive red feldspathic granites with two sets of cleavage lines; 

 the vertical with a strike northeast and southwest, and the other inclin- 

 ing at an angle of thirty degrees ; the strike, southeast and northwest ; 

 while the bedding inclines with the hills. The bedding is so regular 

 and massive that it looks like massive sandstone stratification. The 

 Platte, with all its little branches, flows through these rifts or intervals 

 between the ridges ; one side of the stream, a plain gradual slope ; the 

 other, extremely abrupt, with the rugged ends of the gneissic or granitic 

 rocks projecting out in a most remarkable mamier. After passing 

 along massive granite walls about five miles, we go through four or five 

 miles of singularly banded gneiss, and then massive granite again of 



