54 



CARBONIFEUOUS FORMATIONS AND FAITNAS OK COLORADO. 



di'tciiiiiiiiition may Itc correct, the occurrence at Canyon of tissli remains repre- 

 senting- types commonly regarded as belong-ini;- to tlie Devonian detracts fi-om the 

 fovee of tliis evidence. 



Th(^ oeologic section descrilied in tlic Tenmih' t'oiio," wliicli is not strictly that of 

 the Tenmile district itself so much as of the region imn)ediately .surrounding, may 

 be condensed as follows: 



Trias? , 



Carbonife^ou^J. 



Silurian 



Cambrian 



Section in Tenmile dislrict. 



Feet. 



Wyoming formation: Princiitally .sandstone of an intensely brick- 

 red color; limestones are practically absent. "If the Permian 

 is represented in Colorado, the evidence of which appears to 

 the writer as yet very uncertain, it would be included in these 

 beds, which have evidently been deposited in direct and 

 unbroken succession over the Upper Carboniferous " 1, 500 



Maroon formation: Coarse gray and red sandstone, sometimes 

 conglomeratic, with many irregularly developed beds of lime- 

 stone which are generally nonmagnesian ; the formation is 

 limited by the Robinson limestone below and the Jacque Moun- 

 tain limestone above; both these limestones contain an inverte- 

 brate fauna of Coal Measures type 1, 500 



Weber grits: Mainly coarse sandstone or grits, with a subordinate 

 development of shale and a few thin and nonpersistent dolo- 

 mitic limestones 2, 500 



Weber shale: Transitional between the massive limestone below 

 and the grits above, and consisting of argillaceous and calcareous 

 shale alternating with quartzitic sandstone 300 



Leadville limestone: A typical dolomite of bluish-gray or black 

 color near the top and lighter colored near the base, passing 

 upward into alternations of shale and sandstone; it contains 

 characteristic concretions of chert and is fossiliferous near the 

 top; sometimes much less but never more than 200 leet in 

 thickness 200 



Parting quartzite: Siliceous beds, generally quartzites; these may 

 possibly belong to the Devonian, but because of an unconformity 

 at the top are left with the Silurian 15-60 



Yule limestone: Light drab-colored, rather thin-bedded lime- 

 stones, which are often magnesian and always more or less 

 siliceous 120-160 



Sawatch quartzite: Remarkably pure, white, evenly bedded 

 quartzite, which is conglomeratic at the base and impure above, 

 passing into argillaceous and calcareous shales 160-200 



The correlation of the Aspen and Tenmile sections is indicated in the nomen- 

 clature emplo3'^ed for the formations. 



In his work at Aspen, Spurr notes a considerable thinning of the Sawatch quartzite 

 to the north, and although the Tenmile region is more to the east of Aspen than to 

 the north, the Cambrian there is only about half its thickness at the former locality. 

 In the shales at the top of this formation Cambrian fossils belonging to the Dikel- 



a U. S. Geol. Surv., Geo], Atlas U. S., Tenmile District Special Folio, folio 48, 1898. 



