EECAPITULATION OF PALEOZOIC FOBMATIONS. 205 



but 2,000 or 2,500 feet to the same series, together with an additional 200 to 500 feet 

 taken from PowelFs Mesozoic. King's Triassic is fixed at 2,000 feet, while PowelFs 

 Shinarump, Vermilion Cliff, and White Cliff groups aggregate 2,785 feet, from 

 which, however, must be deducted 200 to 500 feet to represent the lower jjortion of 

 the Shmarump, assigned by King to the Carboniferous. 



Two possibilities, in default of decisive evidence, present claims for considei'ation. 

 The hypotheses that the Wyoming formation represents either the Carboniferous or 

 the Triassic can be supported hj evidence. If the Wyoming beds be placed as the 

 equivalent of the "Upper Coal Measures" of the Uinta Mountains, it must needs 

 follow that its age would be Carboniferous and that the Ti'iassic of the Uinta Moun- 

 tains would be absent from central Colorado. Regarding the former deduction, it 

 will be recalled that Knight found Carboniferous fossils in King's Triassic near the 

 Colorado- Wyoming line, and Darton reports a similar occurrence in the Wyoming 

 formation of the Front Range. To be sure, in Knight's case onlj^ the lower half of 

 beds mapped Triassic by King are proved to be Carboniferous, but it might have 

 the appearance of forcing the correlation to cut off the upper 800 feet as Triassic, 

 especiall}' since the upper beds are similar lithologicallj' and appear to have been 

 deposited in unbroken succession. Further, some of the faunal assemblages found 

 by Knight are strongly suggestive, in the abundance of Bell&ro])lion and Dentalmm, 

 of the fauna of the Bellerophon limestone, and of one which occupies a similar posi- 

 tion at the top of the Aubrey series in the Grand Canyon region. Powell describes 

 this formation as being an indurated calcai'eous sandstone on the south side of the 

 Uinta Range (p. 65), so that the lithologic as well as the faunal facies of the beds in 

 Wyoming are suggestive of the Bellerophon limestone. Barton's evidence is less 

 complete, but tends in the same direction. He identified at Morrison, near the top (?) 

 of the W3'oming formation, strata having the same lithologic character and similar 

 invertebrate fossils to the Carboniferous Red Beds of the Black Hills. Over much 

 of the State the Red Beds (Wyoming formation) are without determinable fossils, 

 except for the two occurrences just mentioned. Unconformably above them rests the 

 Jurassic (Morrison and Gunnison formations). Though commonly referred to the 

 Triassic. these strata, therefore, might really be Carboniferous, so far as intrinsic 

 evidence is concerned, and equivalent to the Upper Coal Measures of the Uinta Moun- 

 tains. Indeed, Emmons states of the Wyoming formation that if any Permian exists 

 in Colorado that series probably represents it. The absence of the Shinarump, Ver- 

 milion Cliff', and White Cliff groups of Powell's Uinta Mountain section (the Triassic 

 of King) might readily be accounted for by the erosion which preceded Jurassic 

 sedimentation. In southwestern Colorado the Carboniferous is followed by a forma- 

 tion (the Dolores) which has the characteristics and position of the Triassic in other 

 parts of the State, which Cross and Spencer aiErm to be the same as the Tria.ssic 



