EECAPITULATION OF PALEOZOIC FORMATIONS. 157 



in this region.'' (Leadville monograph, p. 61.) It will also be remembered that 

 an unconformity occurs at this horizon in the Front Range region, between the 

 Millsap limestone and the underlying beds. 



Spurr identities the Parting quartzite at Aspen. He gives a section (Aspen 

 monograph, p. 13) in which it is seen to comprise 67 feet of dolomite, dolomitic 

 shale, sandstone, and quartzite in thin alternations. At Castle Butte the series is 

 said to consist of a basal impure quartzite, a shaly bed stained a deep maroon color, 

 a heavy light-green lithographic dolomite, and at the top a heavj^ quartzite. Spurr 

 correlates the beds at Aspen having the above characters and a stratigraphic position 

 between the Yule limestone and the Leadville limestones with the Parting quartzite 

 of Leadville and with the upper member of the Yule limestone as it was differentiated 

 and described by Eldridge in the Crested Butte quadrangle. This portion of the 

 Yule is from 60 to 90 feet in thickness and consists of green, 5'ellow, and red and 

 white shale, with more or less calcareous la3'ers, the latter passing into thin lime- 

 stone. The lithologic characters of the bed differ in some particulars from the 

 Parting quartzite at Aspen, and both differ from the formation at its typical 

 localities. 



Emmons identifies the Parting quartzite in the Tenmile district. It there has 

 a thickness of from 15 to 60 feet and consists of siliceous beds, generally quartzites. 

 The possibility of its being of Devonian age is referred to, but it is still retained 

 with the Silurian, chiefly because of the unconformity at its top. 



I have not recognized the Parting quartzite in Peale's Eagle River section, but 

 the strata are there largel}' concealed at the horizon at which it ought to occur. 



At Red Cliff, also, the Parting quartzite is possibly missing. Emmons was not 

 able definite!}' to recognize it, nor is its recognition clear in Tilden's section at Battle 

 Mountain. He found beneath the Leadville limestone the following sedimentaries 

 in ascending series: Cambrian white quartzite, 125 feet; tine-grained sandstone, 100 

 feet; Silurian white quartzite, 5 feet; and conglomerate quartzite, 8 feet. One 

 might infer Tilden's opinion to be that the lowest bed of this series represented the 

 Sawatch quartzite, the succeeding one the Yule limestone, and the third and fourth, 

 probably the Parting quartzite. B}- this interi^retation, however, the Yule is rep- 

 resented by a sandstone, while the Parting formation is reduced to but 13 feet in 

 thickness. As the Sawatch measures 400 feet on Eagle River, not to mention a con- 

 siderable transitional series above it, and 160 to 200 feet in the Tenmile district, all of 

 the siliceous beds at Red Cliff, amounting to less than 240 feet, might, as to thick- 

 ness, without impropriety be referred to the Sawatch quartzite. This, however, 

 involves the local absence of both the Yule limestone and Parting quartzite, which is 

 open to objection but might be explained through the unconformity by which the 

 Leadville limestone was preceded in the Leadville district. While it seems to me 



