THE BASIN* PROVINCE 121 



The Cutler (Permo-Carboniferous) is apparently conformable on the 

 Hermosa in the Ouray district. 



In the same folio (Ouray, No. 153) Girty gives a list of the fauna occurring 

 in the Hermosa and says (page 4) : 



"The fauna of the Hermosa formation occurs also in the Weber limestone and 

 lower Maroon formation of the Crested Butte district, and in the Weber formation 

 of the Tenmile and Leadville districts. From this fact and the similarity in 

 stratigraphic occurrence a correlation of the formations seems to be justified. 

 The Hermosa fauna represents early Pennsylvanian sedimentation, and it is prob- 

 ably older than the 'Upper Coal Measures' faunas of the Kansas and Nebraska 

 section." 



At Rico, Colorado, a distinct series of deposits overlies the Hermosa and 

 is conformable with the overlying Cutler. This deposit seems to be some- 

 what local in character. 



The Rico formation 1 is about 300 feet thick and is made up of sandstones 

 and conglomerates with intercalated shales and thin fossiliferous limestones 

 which are usually sandy. 



"The general characteristics of the Rico formation in the vicinity of Rico are, 

 first, its calcareous nature, in which it resembles the strata above and below; 

 second, the feldspathic constitution and the coarseness of its sandstones, in which 

 respect it differs from the Hermosa and resembles the Cutler; and third, its 

 chocolate or dark-maroon color, which contrasts sharply with the gray or green 

 of the Hermosa and which is more or less distinct from the bright vermilion of 

 the Cutler and Dolores. * * * 



"The bulk of the formation is made of sandstones and sandy shales composed 

 of such materials as are derived from the disintegration of granite. The sand- 

 stones are mostly coarse or conglomeratic, always showing grains of fresh feldspar 

 mixed with mica flakes and quartz. * * * The coarser sandstones are usually 

 cross-bedded and occur in massive beds from 2 or 3 to 25 feet in thickness. Some 

 of the coarser sandstones are of very much lighter color than the mass of the forma- 

 tion. When fine-grained the sandstones are usually somewhat laminated and 

 pass into sandy shales. The shales, aside from the sandy varieties, are of two 

 kinds the fine-grained, unlaminated, red, marly beds, similar to those of the 

 Cutler, and the equally fine-grained, laminated clay shales of a green color. 



"Intercalated with the sandstones and shales, which are for the most part very 

 calcareous throughout, there are several beds of impure limestone, some as earthy, 

 gray, sometimes nodular bands associated with the marly shales, and others as 

 sandy limestone of a red color, in strata from 6 inches to 2 feet in thickness." 



Fossiliferous sandy limestone layers occur as lenses shading into the 

 sandstone both horizontally and vertically. One or two are very persistent. 

 The Rico pass conformably into Cutler with no sharp distinction. 



Cross and Howe 2 give the following statement with regard to the relation 

 of the Hermosa and Aubrey: 



1 Cross, Whitman, and F. L. Ransome, Rico Folio, No. 130, U. S. Geol. Sur., p. 3, 1905. 

 * Cross, Whitman, and Ernest Howe, Red Beds of Southwestern Colorado and Their Cor- 

 relation, Bull. Geol. Soc. Amer., vol. 16, p. 466, 1905. 



