21(1 CARBONIFEROUS FORMATIONS ANIJ FAtlNAS OF COLORADO. 



liad been discriminated. Indeed, had this i'act been known when these formation 

 names were first i)roj)osed it is possible that this course would have been adopted. 



For the Upper C'arl)oiiiferous formations in tiie Uinta Mountains we have the 

 I'inta sandstone, the Ijodore <;'roup, the Red Wall limestone, and the Upper and 

 Lower Aubre}' groups. The names lied Wall and .\ubrey are adopted from the 

 (rrand Canyon region, and, as the correlation of the Red Wall group is certainly 

 erroneous and that of the Aubrey still doubtful, it appears to me that these names 

 should be abandoned for this area. 



In central Colorado we have the Weber formation, the Maroon formation, and 

 possibly the Wyoming formation. 1 take it that the use of the name Weber records 

 the attempted correlation with the Weber quartzite of the Wasatch Range, by which 

 formation the name was long preoccupied. It is doubtful if the Weber formation of 

 Colorado" can be correlated with the Weber quartziteof Utah, and certainly the two 

 formations can not be considered the same geologic unit. Indeed, the Maroon 

 formation is much more probabl}^ to be correlated with the Weber quartzite, 

 a fact which perhaps finds partial expression in the later expansion of the term 

 "Weber formation"' in Colorado so as to include the lower half of the Maroon 

 formation (vide the section of the Tenmile folio). This step has made the free use 

 of the term "Weber" impossible in discussions of Colorado geology, and it seems to 

 me that the name can not be too quickly laid aside in this connection. Endlich's term, 

 "Arkansas sandstone," which was given to the moro or less exact continuation into the 

 Sangre de Cristo Range of the Maroon conglomerate of the Elk Mountains, seems 

 to have been generally overlooked. We have now the Weber quartzite (of the 

 Wasatch Mountains), the Uinta sandstone, the Maroon conglomerate, the Arkansas 

 sandstone, the Fountain formation, the Badito formation, and the Hermosa formation 

 in use for parts or variations of the whole of about the same series of strata. All 

 these names, and especially the Maroon and Arkansas, * will need careful consideration 

 whenever a recension of this nomenclature or further detailed work involving this 

 series is attempted. The variability of the Maroon beds is such, however, especially 

 in view of the disconnected character of the areas of outcrops, as to justify, if not to 

 demand, numerous local appellations. 



The opinion that in the Rocky Mountain region the Archean mountains of to-day 

 represent island masses which have never been completely submerged has had the 

 _ support of eminent geologists from the time that the Rocky Mountains first became 

 the subject of geologic study, and probably no one has given the matter more 

 thoughtful investigation than S. F. Emmons, or more frequently and ably advocated 

 this view. The conception, I think, has its origin in the very obvious overlap of many 



o As the term was first used in the Anthracite-Crested Bntte folio. 



ft The proposal of the Badito formation might have been avoided by more fully ascertaining the relations of the beds, 

 so called, with the Fountain formation or the Arkansas sandstone. 



