208 OAKHONIKKROU.S I-'OUMATIONS AND FAUNAS OF COLORADO. 



iilciiu' of the 'l\'nniil(' district oN-crlies tlie Miiroon (if t\w Crested Butte district seems 

 :iiso iiiipr(iliiil)l(' and is fontriulictcil hy tiic iioniciiclaturc vvliich Knmioiis employs. 

 Tliey are much rather to be considered equivalent. It would, therefore, furthermore 

 result froni Emmons's correlation that the Maroon of the Teimiile district (the ujjper 

 Maroon of the Crested Butte district) occupies in this section the position of the 

 Aubrey limestone of the Grand Canyon section and the Upper Coal Measures of tlie 

 Uinta Mountain and Wasatch Mountain sections. I have elsewhere discussed the 

 evidence which, while not conclusive, indicates that the Upper Coal Measure lime- 

 stone of the Wasatch Mountains, the series called by the same name in the Uinta 

 Mountains, and the Aubre}^ limestone, if not the Aubrey sandstone, of the Grand 

 Canyon, should be correlated. Whether this series is represented b}^ the upper 

 Maroon beds of Colorado, or is represented in the State at all, are points upon wliich 

 there is, so far, little direct evidence. The fauna found b^' Knig-ht just over the line 

 in Wyoming', as already remarked, suggests the Bellerophon limestone of the Uinta 

 section. It is probable that these beds extend into Colorado. From the upper 

 division of the Maroon in the Crested Butte quadrangle, and from the Maroon of the 

 Tenmile quadrangle, scarcely any fauna deserving the name is known. The species 

 that have been found, however, do not greatly disagree with the fauna of the Rico 

 formation, which is supposed to represent the horizon of the upper Maroon. The 

 Rico fauna is superficialh^ somewhat similar to that obtained by Knight, but it is 

 doubtful if a complete study of the latter will result in many instances of perfect 

 specific identitj'. The Rico fauna is also very different from that of the upper 

 Aubrey g-roup of the Grand Canyon. Though the opinion is expressed with hesita- 

 tion, it seems probable to me that the upper Maroon is not equivalent to the Upper 

 Coal Measures of the Wasatch and Uinta sections (the Aubrey limestone of the Grand 

 Canyon section), but joined with the lower Maroon (the Weber grits) is equivalent 

 to the upper part of the Uinta sandstone and to the W^eber quartzite. As to whether 

 the Aubrey sandstone should be correlated with the Weber quartzite and lower 

 Maroon series, as Emmons suggests, and with them be merged in the Uinta sandstone, 

 or overlies the horizon of the Uinta sandstone, I am in doubt. The opinion has 

 elsewhere been expressed that its horizon was above the Uinta, but there is very 

 little evidence upon this point. In any event it is not to the Weber grits, but to 

 the Maroon series of the Tenmile section, or to both combined, that the Aubrej^ 

 sandstone is probably equivalent. 



It is necessar}^, however, to give some further consideration to the tentative 

 correlation of the Weber quartzite and the Maroon series of Colorado implied in the 

 nomenclature employed by Emmons in the Leadville monograph and elsewhere and 

 strongly enforced by a comparison of the Paleozoic series of Colorado and of the 

 Wasatch Mountains. The fauna of the Weber quartzite is not well known. It has a 



