136 CARKUNIFKROUS FORMATIONS AND FAUNAS OF COLORADO. 



Maroon formation, whilo the uj)por heavy sandstone of the Triassic, together with 

 the overlying fhirassic, would represent the Gunnisun foroiation. Peale's Permian 

 and the lower part of his Triassic apparently have no equivalents in the Crested 

 Butte quadrangle, where there is an important unconformity between the Maroon 

 and Gunnison formations; hut they probablv do find expression in the Red Beds 

 which overlie the Maroon at Aspen and other points fartlwr north. The upyjer 

 division of the Maroon has no lithologic equivalent in the Dolores River region. 



Peale's district for the season of 1876" was again called the Grand River 

 district, and the extent and character of the geologic section seems to be similar to 

 that described in the report for 1875. 



On the south side of Grand River there are a few isolated exposures of granitic 

 rock, but neither Silurian nor Devonian was recognized. Upper Carboniferous 

 beds were found in Paradox Valley and in the canyon of the Dolores, but "both 

 the localities noted on the map were seen from a distance, and therefore no details 

 respecting them can be presented. Thej are probably similar to the rocks of the 

 same age showing farther north and west, which were described in the report 

 for 1875 (p. 71). * * * The line separating them from the Trias has been 

 arbitrarily fixed, as the soft sandstones and gypsiferous shales are much like the 

 beds forming the base of the Trias." Another but unimportant outcrop is said to 

 occur on the Grand River below the mouth of the Dolores. 



Speaking of the Juratrias, he says: "The line separating the Triassic from the 

 Jurassic is almost as obscure as that separating the Carboniferous from the Triassic. 

 The line has been drawn lithologicalh^ the massive red sandstone being considered 

 the top of the Triassic." Of the latter, he remarks: "A massive red sandstone, 

 becoming lighter colored toward the top, cross stratified at many places, is the pre- 

 vailing characteristic rock. Its thickness is from 500 to 1,000 feet. The beds become 

 laminated below, and gypsiferous, passing gradually into the Upper Carboniferous." 

 The Jurassic is said to consist of "soft greenish and gray argillaceous and arenaceou? 

 shales and marls near the top, passing into the Lower Dakota sandstone, and dull, 

 reddish, laminated sandstones and shales at the base." 



Along Grand River the lithologic line separating the Trias and Jura is better 

 defined. "The sandstones forming the upper pai't of the Red Beds are very mas- 

 sive, and the shaly beds just above contain thin beds of limestone. Below the 

 massive sandstones come blood-red shales, followed b}' massive sandstones, gen- 

 erally of a deep-red color, although in many places the color fades to almost white. 

 The thickness exposed is nearly 500 feet, which represents only a portion of the 

 formation." 



The correlation of the beds thus briefly described would apparentl}' be the same 



aXJ. S. Geol. Geog. Surv. Terr., Tenth Ann. Rept., for 1876, 1878, pp. 161-185. Ibid., p. 178. 



