RESUME OF LITERATURE. 37 



and his Upper Permian seems to be a portion of the series Avhich Gilbert, lacking 

 paleontologic evidence, referred to the Trias. 



Freeh" has briefly described the geologic section in Congress Can3'on on the 

 occasion of an excursion of the International Geological Congress in 1891. He refers 

 the Red \Yall group to the Lower Carboniferous and the Aubrey group to the Upper 

 Carboniferous. 



It thus appears that the three reports which have been cited agree in referring, 

 on paleontologic evidence, the Red Wall group whollj^ or in part to Lower Carbon- 

 iferous time. Walcott carries the Carljoniferous (Permian) above the tox? of the 

 upper Aubrey group. The following statement from Gilbert is also of interest:* 



''The classification adopted for the Carboniferous rocks in the Grand Canyon' 

 and along the southern margin of the Carboniferous plateau is of local value onlj'. 

 Seventy -five miles to the west, in the Spring Mountain Range, 1 was unable to 

 correlate the series in detail, and eastward, from Canyon Creek to Camp Apache, the 

 progress of a rapid transformation can be traced." 



It seems tliat we can accept Powell's section of the eastern Uintas with some 

 modifications, but not his correlations with the Grand Canj^ou section in the case of 

 the lower beds. Powell seems to fix the thickness of the upper Aubrey, lower 

 Aubrey, Lodore, and Red Wall gi'oups of the Uinta section at over 5,000 feet. 

 King allows only 3,000 to 2,500 feet for the same interval. White, as will appear 

 later, places the thickness at 3,100 feet, which, as it is intermediate between the fig- 

 ures given by Powell and King, is perhaps nearer the true thickness.'' It might be 

 inferred also that Powell had overestimated the extent of the unconformity between 

 the Lodore and Uinta formations. King seems to discredit it altogether, and White 

 states that in his area it -was slight and easy to be overlooked. 



All available evidence points to the conclusion that Powell's Red Wall limestone 

 of the Uinta section is wronglj^ correlated, and with it several other beds. The 

 lower part of the real Red AVall is without doubt of Mississippian age. This has 

 been the opinion held more or less tentativelj' by Meek, Walcott, and Freeh, and 

 we have a Mississippian fauna from it. On the other hand, it is almost certain that 

 the "Red Wall" of the Uinta Mountains belongs entirely in the Upper Carbonif- 

 erous. The few fossils collected from it by Powell at Gypsum and Cataract canyons 

 indicate Upper Carboniferous. The Uinta, sandstone, which underlies it, seems to 

 1)6 rightl}^ correlated with the Weber quartzite, which carries Upper Carboniferous 

 fossils. The Uinta sandstone itself has probably furnished a few fossils of the same 

 age. Powell mentions Carboniferous fossils as occurring in the Lodore group, and 



n Cong. GM. Internat., 5th sess., Compte Rendu, 1893, p. 470. 



!» U. S. Geog. Gcol. Surv. W. 100th Mer., liept., vol. 3, 1875, p. 179. 



f This measurement is exclusive of the Lodore group, which White ii&ys was not present in his area. At the same time, 

 as the Lower and Middle Carboniferous are said to be so lilie one another and so like the Uinta sandstone as to be some- 

 times difflcult to di.itinguisli, it may be that he merely failed to discriminate the Lodore. li really absent an overlap 

 would be indicated above the Lodore, as well as an unconformity below it. Its thickness is but 465 feet. 



