76 CARBONIFEROUS FORMATIONS AND FAUNAS OF COLORADO. 



Stevenson recognized no Triassic in this aroa, which i.s in accord with the 

 mapping of the Crested Butte quadrangle. 



Tlie area of Peale's .survey in 1S78 eniljraced large f.reas of Paleozoic outcrop in 

 central Colorado, and in chapter 4 of his report " a description of the geology of the 

 Elk Mountains is given. Owing to the complicated geologic structure of this region 

 and the absence of detailed geologic maps, of detailed sections of any length, or of a 

 general section, it is difficult for the reader to gain an understanding of the extent, 

 character, and thickness of the geologic sequence there shown. Bearing in mind, 

 however, the sections given in the Anthracite-Crested Butte folio and the Aspen 

 monograph, it is possible here and there to identif}^ with the formations recognized 

 in those works the strata described bj^ Peale. Apparent!}^ the geologic sequence is 

 maintained with reasonable constancy over all the area survej^ed. 



In the quartzite which he refers to the Silurian the Sawatch quartzite can be 

 recognized, while the Yule and Leadville limestones can frequently be identified in 

 his descriptions. His Jurassic is the Gunnison formation. 1 can not but think 

 that for the most part his Triassic, Permo-Carboniferous, and Carboniferous, except 

 such portion of the latter as may belong to the Weber and Leadville formations, are 

 the Maroon formation of the Anthracite-Crested Butte folio. As pointed out by 

 Emmons and Spurr, the bright-red sandstones which in the Aspen region are found 

 to follow the Maroon formation and are referred to the Trias in the Aspen 

 monograph have not been recognized in the Crested Butte quadrangle. Presum- 

 ably they are wanting over the southern portion of the Elk Mountains. Wherever 

 this formation is not present (and considerable of Peale's work lay in the southern 

 portion of the range) his Permian and Triassic belong in the Maroon formation. 

 It is possible that farther north his Triassic maj^ be equivalent to the red sandstone 

 previously mentioned, which I take to represent the Wj'oming formation of the 

 Tenmile folio. The fact is of interest, to which Sjjurr calls attention,* that the 

 Triassic sandstones on Woodj^ Creek were mapped by the Hayden survey as 

 Carboniferous. 



In narrating his observations during the field season of 1875 " this author com- 

 pares the section observed that year in the Dolores River region with other previous 

 sections. In so doing he compiles a genei-alized section for the Elk Mountains, 

 which is more rea,dilj' intelligible than the fragmentar}^ ones of the original report. 

 This section I will quote as follows:*^ 



aV. S. Geol. Geog. Surv. Terr., [Seventh] Ann. Kept., for 1873, 1874, rp. 193-273. 

 b U. S. Geol. Surv., Jlon., vol. 31, 1898, p. 38. 



cU. S. Geol. Geog. Surv. Terr., Ninth Ann. Rept., for 1875, 1877, pp. 29-^101. 

 d U. S. Geol. Surv., Mon., vol. 31, 1898, p. 77. 



