RESUME OF LITERATURE. 105 



Hayclen speaks in some detail of the sections at Colorado Springs and Canyon, 

 referring to the Silurian, at the latter, the sandstones at the base of the section, and 

 600 to 800 feet of limestones lying above. The thickness in the latter case is 

 probably erroneous, for in Peale's section at Glen Erie there are only 300 feet of 

 beds which are, with an}' probability, Silurian. Haj^den compares the sandstone 

 at the base of the section at Canyon with "the Potsdam sandstone as seen in other 

 localities farther to the north." But the sandstone at Canyon is Ordovician in age, 

 and not Cambrian. "This sandstone passes up into a hard and rather massive 

 limestone, evidently the same as that noted at Coloi'ado Springs.'- This correlation 

 is a very natural one, but at the same time is probably incorrect, for the limestone 

 at Canyon, what part of it is not Carboniferous in age, is the Fremont limestone, of 

 which Cross states that it has not been recognized in other sections along the east 

 base of the mountains. 



Of the Carboniferous he speaks in a general way, touching chiefly upon its 

 distribution. He says: 



"The Carboniferous group is a little more persistent, and yet this seems to be 

 wanting over extended intervals unless a portion of what have been called the Red 

 Beds is of this age. This group is extensively exposed along the flanks of the moun- 

 tains 100 to 150 miles north of Cheyenne, as was shown in the annual report of 1870. 

 It seems, however, to diminish somewhat in force and to contain comparatively few 

 fossils in its southern extension until we reach Cafion City. From thence south- 

 ward into New Mexico it increases again in thickness and importance, and yields an 

 abundant supply of its characteristic fossils." 



The Red Beds he refers to the Triassic, with some admitted uncertainty on 

 account of the general lack of fossils. This group, he says, "is very persistent, 

 and if absent at all, only at ver^'^ short intervals." " Geographicallj^, it is one of the 

 most widely distributed formations in the West. From the northern boundary to 

 the southern line and east of the Wasatch Range in Utah this red formation makes 

 its appearance wherever a mountain range is elevated so as to expose the various 

 sedimentary groups. The evidence indicates that it extends without any important 

 interruption over the broad area as defined above." He states that this series varies 

 in color from a pale, didl tint to a deep purple, in texture from a rather coarse con- 

 glomerate to a fine sandstone, and in thickness from 100 feet to 2,000 feet. He 

 remarks (page 13) that he formerly held the view that the elevation of the Front Range 

 was a single event and comparatively modern, and that the changes in the position of 

 all the groups were brought about b}' the same cause and at the same time. ' ' There 

 could not be a strict conformity in the sedimentary groups, inasmuch as entire groups 

 are wanting, and in some cases only fragments of others are remaining." "We 

 now have the evidence, from the texture of these Red Beds and their position on the 



