CHAPTER 11. 



THE LIGNITIC GROUP AS EXAMINED AT CANON CITY — COLORADO SPRINGS— NORTHWARD 

 TO CACHE LA POUDRE CREEK — MONUMENT CREEK GROUP — PROBABLE AGE OF 

 THESE GROUPS. 



Our examinatioDS along tlie eastern base of tbe mountains in Colorado 

 were directed mainly to tbe trjji;ing-out of the connection between tlie 

 Liguitic group and the older beds. We traced the boundary of this 

 group, with great care, from Canon City, on the Arkansas River, north- 

 ward nearly to Cheyenne. It is hardly possible that any links in the 

 chain of evidence escaped us, and the principal differences of opinion 

 now will consist in the degree of importance to be attached to that evi- 

 dence. The question is whether the coal-bearing strata known as the 

 Lignitic group of the Eastern liocky Mountain region is of Cretaceous 

 or Tertiary age. In this chapter, we shall simply record our field-obser- 

 vations, referring the reader to a subsequent chapter for a brief discus- 

 sion of the question of age. 



South of Caiion City, on the south side of the Arkansas Kiver, there is 

 an isolated coal-basin occupying an area of about fifty square miles. Tiie 

 strata lie for the most part in a nearly horizontal position, indicating no 

 great disturbance, except along the north and west sides. On the north- 

 west side of the basin, along the immediate base of the mountains, the beds 

 have been lifted up, so that a great thickness of t he Lignitic sandstones is 

 exposed, at least 1,000 to 1,500 ieet. The Cretaceous beds are also seen 

 lying close to the flanks of the mountains. As we proceed southward 

 along the junction of sedimentary beds and the granites, the Cretatjeous 

 beds disappear, and one by one the lower Lignitic, until the whole 

 mass juts against the granitic rocks, with no perceptible evidence 

 of disturbance, except in a general way. There seems to be a rapid 

 slope from the base of the mountains to the Arkansas Eiver, a dis- 

 tance of about five miles, thus giving to the strata a general dip of 

 about 5°. So far as we could ascertain, there are no coal beds in. 

 the noithern portion ot the basin. The rocks consist mostly of rath- 

 er thick beds of gray, brown, and yellow sandstone, with loose clays 

 and sands between, but no coal beds. We find that the coal-bear- 

 ing portion does not occupy the entire area, and that a large part is 

 classed as barren coal-measures. The most important coal-mine has 

 been opened on the east side of the basin, about midway, on Oak Creek. 

 This is one of the most important coal-mines in the Territory. It was 

 described briefly, but quite clearly, in the Annual Report of the Survey 

 for 18G9, and since that time in the more elaborate reports of Mr. Les- 

 quereux. In the summer of 1872, Mr. Lesquereux made a cj^reful 

 examination of the coal-formations all along the east base of the Rocky 

 Mountains from Cheyenne to Santa Fe. His report in the Annual Re- 

 port for 1872 is quite exhaustive. The section of the coal-strata on 

 page 323, made by Mr. j^eilson Clark, the superintendent of the mines, is 

 more accurate than any other that has been made of the group, and need 

 not be repeated here. It remains now to consider the beds below this sec- 

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