lili CARBOMIKKROtTS FOKMATIONS AND FAUNAS OK COLOKADd. 



\ii'\v of st)nu'\vliul cDiilliftiiiL;' c'N'iclcncc ii[H)n tliis point, 1 slioukl dcsiri; to sci; lliese 

 iilcnlitications corrobonitod. uiul also tlii' adilitioiuil ovideiu'e of a larger iioni or 



flUlllll. 



Stcven-son also describos a section, made on the forks of Eagle Kiver, at nearly 

 the same point at which that made ])y Peale was taken. At the base lies the 

 Leadville limestone, some 300 feet above which is found a conglomerate 40 feet in 

 thickness, followed innncdiately by li.OOO feet of sandstone, shale, and conglomerate, 

 including gypsum beds. Reddisii gra\' and yellow seem to be the prevailing colors. 

 Tlien come in about 500 feet of sandstones interbedded with limestones, some of 

 which contain Carboniferous fossils. The limestones are blue, and the sandstones 

 reddish, gray, brown, etc. The upper iiiember contains 2,500 feet of coarse sand- 

 stone,, mostly of reddish-graj- color and entire!}' without limestones and shales. It 

 is this member of the section to which Stevenson later compares the upper portion 

 of the Arkansas sandstone in the Sangre de Cristo Range. Stevenson apparently 

 did not observe the series which is called bj^ Peale Triassic, and for which the local 

 name, Wyoming formation, is employed in the Tenmile district. No beds .similar in 

 position and lithology to the Weber shales or limestone can be discerned in this 

 section unless the space of 200 feet at the base contains them. All these strata, 

 therefore, would appear to belong to the Maroon formation of the Crested Butte 

 district oi- the Weber grits and Maroon of the Tenmile district. The peculiarities 

 of this section, among which may be mentioned the segregation of the limestones 

 near the middle, the gypsiferous nature of the lower portion and the character and 

 coarseness of its conglomerate beds, and the dark color of the upjjer portion which 

 is compared with beds in the Sangre de Cristo having a reddish-brown tint, are 

 probably not to be found together in anj- one of the described sections, and illustrate 

 the great variability in detail of this series from point to point. 



In the Tenmile district the Upper Carboniferous formations discriminated by 

 Emmons are the Weber and Maroon; the Wyoming formation, above, is placed in the 

 Trias. Of the Weber formation he I'ecognizes two divisions, the Weber shales and 

 the Weber grits. The Weber shales, which appear to be the equivalent of the Weber 

 formation of the Anthracite-Crested Butte folio and the Aspen monogi'aph, are 

 described as consisting of argillaceous and calcareous shale alternating with quartzitic 

 sandstones. Beds of impure limestone contain Coal Measure fossils. The thickness, 

 which is vexy variable, is assumed to be about 300 feet. The Weber grits are part of 

 the series elsewhere described under the name of Maroon conglomerate. The forma- 

 tion here distinguished bj^ that name has an average thickness of about 2,500 feet. 

 It consists mainlj' of coarse sandstones, or grits, often A'ery micaceous, with a subor- 

 dinate, development of shales and a few thin and uonpersistent dolomitic limestones. 

 The sandstones are generally light gray in color, and their prominent constituents . 



