78 CAUHONIKKROUrt FORMATIONS AND FAUNAS OF OOLOBADO. 



Klk .Mduiitaiiis. AMicrcver Peale cites the Permiiui or tlic Ti'iii«.sic from this I'egion, 

 therefore, the l)eds probably t'onn part of the Maroon formation. Farther north 

 the beds so denominated may be equivalent to the "Lenado" sandstone on the one 

 hand and in a more or less general way to this author's Permian and Triassic in other 

 areas. Accordingly, thus qualified, the Permian of the Elk Mountains combined 

 with the Carboniferous represents the Carboniferous and Permian of the Eagle 

 River, with the exception of the upper 800 feet of the latter. This, together with 

 the Triassic, would according!}^ lie equivalent to Spurr's Triassic about Aspen and to 

 Peale's Permian and Triassic in the Elk Mountains wherever, if at all, these do not 

 belong in the Maroon. Similarly, the Permian and Carboniferous combined of the 

 Elk Mountains are equivalent to the Permian and Carboniferous of the Park Range, 

 both representing the Maroon formation of the Crested Butte quadrangle. The 

 Triassic of the Park Range, according to my view, is the same as Spurr's Triassic at 

 Aspen, and probablj' has no equivalent in Peale's Elk Mountain section except, 

 l^erhaps, sporadicall3^ 



The reports b^^ Hay den and by Holmes" (chapters 5 and 6) upon explorations in 

 the Elk Mountains during, the vear lS7-i are desci'iptive in character and devoted to 

 a discussion of the structural rather than of the historical geology of the area. One 

 can recognize in their descriptions the Sawatch quartzite, the Maroon conglomerate, 

 and the AVyoming sandstone, but the observations recorded are of a general charac- 

 ter, and while agreeing with the section described itl the Anthracite-Crested Butte 

 folio add little or nothing to it except perhaps in the matter of distribution of the 

 formations. Both authors speak of the gradation through the Red Beds into the 

 well-established Carboniferous, and as a result of this circumstance and of the com- 

 plicated geologic structure the Red Beds are united with the Carboniferous under a 

 single color in the geological map accompan3'ing their report. In the present 

 instance the term Red Beds is employed for the bright-red "Triassic" series, the 

 maroon-colored series being correctly referred to the (Carboniferous (p. 62). 



SOUTH PARK REGION. 



Though situated at the extreme northern end of the Mosquito Range, the 

 Leadville section would naturall}' be selected to compare with the less formal 

 reports of earlier work dealing with the South Park region. Except for a few 

 changes in the matter of formation names, the section described in the Leadville 

 monograph* is practicality the same as that of the Tenmile folio, which, though that 

 area is almost contiguous with the Leadville district, has been considered in connec- 

 tion with the geology of the Grand River region. Both the Leadville monograph 



aV. S. Geol. Geog. Surv. Terr., [Eighth] Ann. Kept., for 1874, 1876, pp. 54-58 and 59-71. 

 (>U. S. Qeol. Surv., Mon., vol. 12, 1886. 



