RECAPITULATION OF PALEOZOIC FORMATIONS. 195 



the Maroon in the Tenmile and Leadville districts. It is not clear, however, that 

 this bright-red series may not a^ter all be present in the Crested Butte quadrangle, 

 for in the northern portion, where the greatest thickness of the Maroon occurs, the 

 rocks of this formation are bleached and greatly metamorphosed (Crested Butte 

 folio). Nevertheless, one would expect some equivalent of the Dolores formation 

 to appear, with its characteristic color character, in the southern portion of the 

 Crested Butte area, unless it were cut out, owing to the pre-Gunnison unconformity. 



In the Dolores River region the Upper Carboniferous, according to Peale, in 

 whose accounts almost the only descriptions of the Paleozoic strata of this region are 

 found, consists of light-yellowish and greenish shaly sandstones and a sj)ace filled 

 with shalv sandstones and perhaps bands of limestone, the whole amounting to 3,500 

 feet. This series rests upon a blue limestone about 300 feet in thickness, referred to 

 the Subcarboniferous, and is overlain hy the "Permian." This has at its base 300 

 feet of yellowish and black shales and sandstones, with gypsum and salt, and 700 feet 

 of pink and red shales, with conglomerate, the sandstones becoming light colored 

 near the base and containing gypsum. The upper bed of the Permian is unlike the 

 lower and unlike the rest of the Carboniferous, and as it seems to partake of the 

 chai'acter of the Red Beds above, it appears more appropriate to unite it with Peale's 

 Triassic, the lower portion possibh' being joined with the Carboniferous, which 

 would then have a thickness of 3,800 feet. 



Lithologically this series appears to be the equivalent of the Hermosa formation 

 of the San Juan region, while by the Red Beds above, the Dolores and La Plata 

 formations are represented. The Rico formation, which foiins a part of the San 

 Juan Red Beds, appears to be missing, or to have lost somewhat its distinctive color, 

 for Peale describes no brownish or maroon-colored beds in his Permian or Ti-iassic 

 series. The nearest instance is the blood-red sandstone and shale of his Trias, 

 which ai'e over 700 feet up in the Red Beds. This point is interesting, and it is to 

 be regretted that the evidence by which a satisfactory conclusion can be reached is 

 lacking. If, however, my correlation of the Rico with the upper part of the Maroon 

 is justified, by which the thickness is reduced from 2,500 feet in the Crested Butte to 

 300 feet in the San Juan region, its complete disappearance in the Dolores region is 

 not surprising. The fact mentioned by Eldridge, that the upper Maroon is greatly 

 diminished in thickness in the southern part of the Crested Butte quadrangle, is 

 distinctly favorable to its correlation with the Rico. The upper portion of Peale's 

 Permian, taken with his Triassic, and possibly in places with a portion of his Jurassic, 

 are the probable equivalent of the Dolores and La Plata formations, as the Jurassic 

 is of the McElmo; but these formations appear to lie of reduced thickness in Peale's 

 area. 



The Carboniferous of Peale, even without the 300 feet of "'Permian" which 1 



