RECAPITULATION OF PALEOZOIC FORMATIONS. 207 



recentl}'' found by Knight in the Triassic of tliis area to that of the Belleroplion 

 limestone has already been remarked. The Jurassic comes onlj^ 800 feet above these 

 Carboniferous horizons in Knight's section, and it is necessary to conclude either 

 that the Triassic is wanting at this point, and erroneously represented there by King, 

 that it is represented by these upper 800 feet, even though they are lithologically 

 like the Carboniferous beneath and apparently continuous with it, or that the Tri- 

 assic, nowhere in this area determined by fossils, is realh^ Carboniferous, the series 

 being in fact a unit detei'mined as to age by the Carboniferous faunas occurring 

 invariably' in the lower portion. Probabilit3% in my judgment, as already remarked, 

 weighs moi-e heavily in favor of regarding the Carboniferous and "Triassic" of this 

 region as two separate series, the upper one correlated with the Triassic of more 

 distant areas where Triassic fossils are found. 



The interesting discovery b}- Knight, above referred to, I believe to represent 

 the Carboniferous which King describes as comprising 1,500 feet on the west side 

 of the Front Range, the same thickness as all of Knight's Red Beds below the 

 Jurassic. The absence of the Triassic at this point, if, as seems rather more prob- 

 able, it is not represented by the upper unfossiliferous series, is by no means without 

 pi'ecedent, and is easily to be accounted for by the erosion period which preceded 

 the Jurassic sediments. It appears not improbable that some of the sediments now 

 supposed to represent the Maroon formation should really be assigned to this divi- 

 sion (i. e. King's Upper Coal Measures). The Weber grits and Maroon formation 

 of the Tenmile district, for example, hick at least the distinctive color of the 

 original Maroon, as does the corresponding series on Eagle River. 



As regards the general similarity of the two formations in Colorado, a similarity 

 which is not obvious when only the section given by Powell is considered, reference 

 may be made to White's remark tliat his Lower Carboniferous so resembles the 

 underlying Uinta sandstone, and his Middle Carboniferous the Lower, that in some 

 cases it was difHcult to distinguish them. 



Emmons states in the Tenmile folio that the Weber formation of that area repi'e- 

 sents in a general way the Weber quartzite of Utah and the Lower Aubrey group of 

 Arizona. This implies that the Aubrey sandstone, the Weber quartzite, and the 

 Weber grits or lower Maroon, are of the same age. As a corollary they would 

 probably represent the upper portion of the Uinta sandstone. There seems to be no 

 reason why the upper and lower Maroon should not be made two distinct, possibly 

 as to age two rather different, series. That the Weber grits and Maroon beds of the 

 Tenmile district represent a higher horizon than the Maroon series of the Crested 

 Butte district, seems to me altogether out of the question, because, for one reason, 

 the fauna of the Weber grits is so similar to that of the lower Maroon that a correla- 

 tion of them can probably be made on this evidence alone. That the Maroon series 



