KESUME OF LITERATURE. 63 



The most satisfactory course seems to be to consider the latter an expansion of the 

 upper or transitional portion of the Sawatch quartzite. Described as it is in Peak's 

 section, this series would hardly be regarded as part of the Yule limestone of the 

 Aspen section. At all ev^ents, the siliceous beds at the base of the section have a 

 greater development on the Eagle River than either at Aspen or in the Tenmile 

 district. The Yule limestone, though thicker than in the latter area, is somewhat 

 thinner than at Aspen. Taken together, the Cambrian and Silurian beds, 823 feet 

 in thickness, are slightly in excess of the combined maximum measurements of the 

 two series at Aspen, and greatly more than their combined measurements in the 

 Tenmile district. It would appear that the lower portion of the section, especially 

 the siliceous part, is thickening rapidly toward the northwest. This inference 

 receives confii'mation from a remark by Peale" to the effect that " there was a much 

 greater development in Mr. Marvine's district." This statement refers to the 

 Silurian beds, under which term it must be remembered are included both the 

 quartzitic and the calcareous strata mentioned above. 



The limestones at the base of the Carboniferous portion of the section occur just 

 above those given in the section of the Silurian. The lowest of these evidentlj" 

 belongs to the Leadville limestone, and the beds above, which appear to be mainly 

 calcareous, must represent the Weber formation or ^^'^eber shales of the othdr sections. 

 In spite of the fact that Peale says, referring to beds 25 and 26, that "The remainder 

 of the section to the beds I included in the Devonian? is as follows," indicating that 

 the Devonian occurred below bed 26, it is quite clear from remarks on the opposite 

 page* that beds 25 and 26 are the ones which are regarded as belonging to this period. 

 The reference of these beds to the Devonian seems' to be largelj' hypothetical, and is 

 in part certainly erroneous, while it may be in part afso correct. 



I am satisfied, from the lithologic character, the position in the section, and to a 

 certain extent from the fossils, that bed 26, whose thickness is not given, is the 

 Leadville limestone of later reports. This formation is known at so many and so 

 widely separated localities to contain a Devonian fauna in its lower portion that it is 

 probable the same occurrence will be found at this point also. 



Bed 22, from its lithologic character and relative position, can safely be referred 

 to the Maroon formation, or Weber grits, as it is alternatively called. As the 408 

 feet of beds immediately below, which are said to be concealed for the most part, 

 consist of micaceous shales and sandstones in the upper portion, with limestone at 

 the base, it seems probable that a portion of bed 23 also belongs in the Maroon. 

 From the limestone is cited a fauna which is probably of Upper Carboniferous age. 

 As the Leadville limestone contains a Mississippian fauna it is necessary to conclude 

 that the base of 23 belongs in either the Weber or the Maroon formation, the age of 



aU. S. Geog. Surv. Terr., [Eighth] Ann. Rept., for 1874, 1876, p. 110. 6 Ibid., 114. 



