HA YUEN.] 



GEOLOGY COLOEADO EANGE. 35 



tlie facilities aiforded by these natural sections, only a iiartial examina- 

 tion was made. There is an area here of about ten or fifteen miles square 

 that must ever remain an interesting field for the practical geologist 

 and deserving of a special exploration. One may follow Williams's 

 Canon up two or three miles above the springs through a narrow gorge with 

 walls rising 300 to 500 feet on either side. At the entrance to the canon the 

 red beds rest on a yellow-gray limestone which passes down into an 

 arenaceous limestone with a reddish tinge containing well-marked Silu- 

 rian fossils. The inclination of all the beds is about 35°, and the mass 

 runs high up on the mountain-sides, resting unconformably on the 

 coarse feldspathic granites, as shown in thg illustration. The lowest 

 beds of sedimentary rocks are rather coarse sandstones, and conglomer- 

 ate made up of water- worn quartz-pebbles, with very irregular laminae 

 of deposition, the whole reminding one of the Potsdam group. Abdut 

 two miles up the caSon the Silurian beds, inclining southeast 8° to 10°, 

 rests on the feldspathic granites, which are most distinctly stratified, 

 the strata inclining about north 35°. The sedimentary beds fill up in a 

 remarkable manner the inequalities of the original surface of the meta- 

 morphic rocks. The Silurian group was noticed by me in 1869, and a col- 

 lection of fossils was made, but the fossils were not identified by Mr. 

 Meek until it was too late to use them in my third annual report. In 

 the fourth annual report, 1870, on page 295, several species of Silurian 

 fossils are mentioned by him belonging to the collections from this 

 locality. One of the species, according to Mr. Meek, is a well-known 

 form in the Calciferous group of New York, OpMleta complanata. 



There is considerable variety in the aggregate of beds here, which 

 may be. regarded as Silurian, and we may conclude that the Potsdam 

 group is quite well represented, and that it is possible that some of 

 the higher divisions occur. These rocks require a still more careful 

 study, yet it is an interesting fact to know of their existence in this 

 locality. In the lower sandstones I found a species of Lingula, the pres- 

 ent season, i)robably a Potsdam form. I have never known of any Car- 

 boniferous fossils being found here, but I am confident that there are 1,000 

 to 1,500 feet of these beds between the Silurian group and the true red 

 beds or Triassic. They are composed mostly of sandstones, quartzites 

 with partings of clay variegated.. About four miles to the north the 

 Silurian limestones form high ridges on the sides of the mountains for 

 a short distance, then disappear entirely. There seemed to be an ap- 

 parent Unconformability here. I studied the structure of the upturned 

 edges from every point of view, and I could not decide on a real non- 

 conformity. There were localities where the Silurian group is entirely 

 separated from the red beds, and inclining at different angles, but at 

 the upper end of the "Little Garden of the Gods" the order of sequence 

 appeared to be unbroken. We may now ask how 2,500 to 3,000 feet 

 of rocks disappear so quickly and mysteriously, as we go north of 

 Fountain Creek. The red sandstones that we have been in the habit of 

 regarding as Triassic rest upon the granites as if they had been deposited 

 there by water originally, but partook of the elevation of the mountain- 

 range. We may suppose that the Silurian beds once covered this entire 

 region, and that over large areas they were worn away prior to the 

 deposition of the overlying beds, and that the portions we see at this 

 locality are remnants that escaped the great erosions, or we may suppose 

 that they were not deposited. I believe the former is the true inter- 

 pretation, that the Silurian rocks once covered the entire country and 

 may still exist to a greater or less extent under the vast thickness of 



