EESUME OF LITERATURE. 39 



time. As I have already shown, the faunas from the eastern portion of the Uinta 

 Mountains, supposed to come from the same horizon, are almost entirely different. 

 The peculiar and striking forms, whether of the Aubrey group of the Grand Canyon, 

 or of the Upper Coal Measure fauna of the Wasatch Mountains, seem to be absent. 



Another circumstance adverse to the correlation consists in the thickness of the 

 formations supposed to be equivalent. The t3^pical Aubrej^ group has a thickness of 

 but 1,800 feet, while the Lodore, Red Wall, upper Aubre}', and lower Aubrey groups 

 of the Uinta Mountains, according to Powell, amount to 5,000 feet, though, as 

 already noted, White assigns 3,100 feet and King but from 2,000 to 2,600 feet to the 

 same formations. It is a fact not perhaps without suggestion, that if to the Aubrey 

 group l)e added half the thickness of the Red Wall limestone, the upper portion of 

 which is known to be of Pennsj'lvanian age, the total (3,070 feet) is almost precisely 

 the same 'as AVhite's measurement in the Uinta Mountains, which is nearly a mean 

 between King's and Powell's. Upon this point — whethei- the Pennsj'lvanian portion 

 of the Red Wall limestone is missing from the Uinta section, or is represented by 

 part of King's Upper Coal Measures, there is very little evidence. There exists, 

 however, such an analogy between the sections of the Wasatch Mountains, the Grand 

 Ciinyon region, and central Colorado, where each shows a limestone series which 

 is in part Mississippian and in part Pennsylvanian (the Wasatch limestone in the 

 Wasatch Mountains, the Red Wall limestone in the Grand Canyon, and the Lead- 

 ville and Weber limestones in the Crested Butte section), that I am disposed to 

 assume uniformity in other respects, and to believe that the whole of the Red Wall 

 limestone is missing in the eastern Uintas, just as all the Wasatch limestone and the 

 Leadville and Weber formations are supposed to be. According to this correlation, 

 then, the Devonian, Mississippian (lower Red Wall), and lower Pennsylvanian (upper 

 Red Wall) wedge out as the eastern Uintas are approached." while the Weber quartzite, 

 whidi is supposed to come above them, disappears southward. The unconformity 

 which Powell noted between the Lodore group and the Uinta sandstone might be 

 cited as a cause for the removal of this series in the Grand Canyon region. 



The occurrence of great Algonkian (?) masses in the Grand Canyon series of the 

 Grand Canyon, in the quartzites of the Needle Mountains in Colorado, and in the 

 Red Creek quartzite of the Uinta section, suggests that a band of this series, having 

 an approximate north-south trend, may extend through this region. 



The year following the publication of Powell's report upon the Uinta mountains 

 appeared the second volume of the reports of the Fortieth Parallel Survey.* In 

 discussing both in this place and later the import of the data collected by this 

 organization, it will not be necessary to contrast and distinguish between the views 



a Probably owing to the same agency which destroyed the supposedly equivalent series still exisiting in northern 

 Utah and central Colorado, erosion prior to the Weber quartzite. 



bV. S. Geol. Expl. iOth Par., Kept., vol. 2, Descriptive Geology, 1877. 



