DISCUSSION 527 



Another point in the evidence is the existence of the above-described 

 unconformity in the midst of the Carboniferous. Its presence, whether 

 marking a great interval or a comparatively short one, nevertheless 

 lengthens Carboniferous time by just so much. The facts as already 

 stated seem to the writer to argue a considerable time break. The effect 

 is to increase the improbability of. such immense thickness of Carbon- 

 iferous strata. It is recalled here that Powell considered the break in the 

 eastern Uintas one of considerable time value*, and notes that the break 

 increases toward the southeast. 



There is no evidence either for or against an uncomformity between 

 the basal quartzite and succeeding formations on the south flank in the 

 western Uintas, since the contact there is marked by a fault whose throw 

 of probably several thousand feet brings later shales and quartzites 

 squarely against the basal member. 



Emmons' remarks of the Fortieth Parallel region that both limestones 

 and shales become increasingly silicious toward the east.* This is con- 

 sistent with the idea that a land area lay eastward, and one should 

 expect a rather complete change in the nature of corresponding beds in 

 that direction, with possible thinning and occasional actual breaks in the 

 succession. 



If the pre-Paleozoic floor may be assumed to rise toward the east and 

 the Paleozoic sea has encroached on it from the west or northwest, then 

 we should expect equivalent beds of somewhat unlike lithologic char- 

 acter in widely separated areas. Limestones of the Wasatch might cor- 

 respond to shales in the Uintas, sandstones to conglomerates, shales to 

 sandstones, and in local oscillations some beds might be entirely missing. 



In the Wasatch the " Weber quartzite " is both preceded and followed 

 by limestones that are highly fossiliferous and upper Carboniferous in 

 age. 



In the Uintas there are no Paleozoic sediments found preceding the 

 basal quartzite, and the description of the later formations varies for 

 different parts of the region. Powell gives 4,000 feet of limestones and 

 shales and sandstones partly fossiliferous, but with the lowest member 

 of his series (the Ladose group) missing in the southeast. Emmons 

 gives gray limestone, calcareous sandstone, and cherty limestone as the 

 general succession. The writer has found in the western Uintas 3,000 feet 

 of shales and sandstones and as much more of quartzites and limestones 

 above the basal member — only the upper members being fossiliferous. 



The Weber of the Wasatch is the last great quartzite of the Paleozoic 

 series. In the western Uintas there are two strongly developed quartzites 



*U. S. Geological Exploration of the Fortieth Parallel, vol. ii, p. 199. 



