RESUME OF LITEKATTJRB. 77 



Generalized section in the Elk Mountains district 0/1373." {After Peak.) 



PERMIAN. 



Feet. 

 Maroon-colored sandstones and shales, with conglomerate at base. K"o fossils. Thick- 

 ness not estimated _ 



COAL MEASURES. 



Yellowish-gray and reddish sandstones and shales, with bands of limestone. Lower part 

 of aeries is gray and greenish micaceous sandstones. Fossils. Third layer (top), 

 Loxonema, 6 Productvs muricatiis, Spirifer; second layer, Productus imn'icatu.i, Athyris 

 suhtilita, Rhynchonella osagensis, Hemiprointes crassus, Terebratvla bovidens, Retzia punctn- 

 lifera; first layer, Productus muricatus 1, 300-2, 000 



SrBCARBOXIFEROUS. 



Limestones and limestone shales. Beds so distorted that thickness not jjositively taken. 



Fossils of Subcarboniferous type not yet examined 



[Total] 4, 000-4, 500 



The most appropriate sections with which to compare the foregoing are those of 

 the Crested Butte quadrangle and of the Aspen district. It is clear that the lowest 

 member of Peale's section represents in a general wa}^ the Leadville limestone, but 

 it maj' also include the Weber formation, for the lowest beds of the " Upper Cai'bon- 

 iferous," just above those from which the fossils are cited, probably belong to the 

 Maroon conglomerate. This is the conclusion at which I have arrived from a study 

 of the original detailed section given on page 251 of the Annual Report for 1873. 

 Both the Carboniferous and Permian of Peale's generalized section of 1875 seem to 

 belong in the Maroon formation, at least so it appears from the lithology of the upper 

 beds and the thickness of the lower ones. The Permian, however, Peale correlates 

 with the Permian of the Dolores River, the Eagle River, and the Park Range. Upon 

 one hypothesis the Coal Measures and Permian combined of the Elk Mountains sec- 

 tion are equivalent to the Coal Measures and the lower portion of the Permian of the 

 Dolores River region, the boundary' in one case passing above the Permian and in the 

 other through it. Upon another hypothesis the Permian of the Elk Mountains, sup- 

 posing it to have the same limits as the upper division of the Maroon, is missing in 

 the Dolores River I'egion, the Coal Measures and the lower part of the Permian of the 

 latter being equivalent to the Coal Measures of the Elk Mountains. 



The real equivalent of mo.st of the Permian (and of most of the Triassic) in the 

 Dolores section seems to be the bright-red sandstone described by Spurr from Lenado 

 Canyon in the vicinity of Aspen. This formation is apparently not found at all in 

 the Crested Butte quadrangle, and probably not at all in the southern portion of the 



oSee pp. 21, 225, 230, 232, 247-2M, report of 1873. 



''In modern terminology these forms are of cour.se Loxonema, Marffinifera min-icata, Spirifei', Margivifera murkata, 

 Seminula subtiUta, Pugnax Utah, Dcrbya crassa, Dielasmo. bovidens, and I-Tustedia mormoiii. 



