•158 CARBONIFEROUS K0RMATI0N9 AND KAUNAS OF (M)L()KADO. 



iiioro iirohalile tliat at Red Cliff all the l)cd.s below the Lcadville linu'stone belonif to 

 the Sawatch (|iiart/Jte, it is quite possible that the rartiiiy formation also is 

 included, as indicated by Tilden. 



Spun-, as we have already seen, correlates with the Parting (juartzite the varie- 

 gated shales which form the upper division of the typical Yule limestone in the 

 Crested Butte district. What may be the same series is described bj^ Endlich as 

 occurring in the southern part of the Elk Mountain region, south of the Gunnison 

 River, in an isolated area called upon the map Fossil Ridge. The series here seems 

 to resemble that in the Crested Butte in position, but shows a remarkable increase in 

 thickness. It apparentlj^ comprises 80 feet of j'ellow and gray shales ovei"laid by 1Y6 

 feet of variegated shale, parti}' sandy, with isolated banks of limestone. . These beds 

 occur above a thickness of limestone that can with a high degree of probability be 

 identified as the Yule limestone and below another sei'ies of limestones from which 

 a Mississippian fauna is cited. The character, thickness, and position of the lower 

 shale especiallj' are such as to correlate it with the upper division of the Yule, 

 which, according to Spurr, represents the Parting quartzite. Though to regard the 

 upper shales as forming part of the same series gives the formation a thickness not 

 known at any other point, this course seems more natural than to join them with the 

 Leadville series. 



In the Grand River region the Parting quartzite occurs at Aspen as identified 

 by Spurr, and in the Tenmile district as identified bj^ Emmons, but it seems to be 

 absent at Red Clifl:' and may not be present on Grand River. At Fossil Ridge, at 

 Crested Butte, and at Aspen this formation seems to lack some of the qualities that 

 characterize it at Leadville, being composed, apparently, largely of shales, some of 

 which are sandy and some calcareous. In the Tenmile district, however, the compo- 

 sition of the formation is more typical, and it consists for the most part of quartzite. 



In the South Park district tlie Parting quartzite occurs at Leadville, which is 

 indeed its typical area, and it is probably to be found more or less continuously south- 

 ward to the Arkansas. As part of the Silurian of Stevenson it is described as having 

 this distribution, and the Hayden atlas shows the Silurian color continuously along 

 the west side of South Park. Stevenson gives two sections in which this formation 

 can be recognized. In that made at Fourmile Creek there appear to belong to it 

 170 feet of quartzite the upper portion of which is- a conglomerate. These beds 

 occur above a limestone which can probably be con-elated with the Yule, and below 

 another upon which the Leadville limestone presumably rests. Though Stevenson 

 includes the overh'ing limestone in the Silurian, it would seem more appropriate to 

 close the Parting quartzite with the siliceous beds and refer the limestone provi- 

 sionallj^ to the Leadville. 



A second section was made by Stevenson in the canvon of the Arkansas on the 



