UNCONFORMITY 525 



immediate break. It marks a time interval also of sufficient length for 

 the consolidation of the rock and the development of a cherty facies, thus 

 converting the cherts and other rock of the floor into suitable materials 

 for succeeding accumulations. 



S. F. Emmons* describes a conglomerate of uncertain relationship in 

 the region just north of La Motte peak, a locality on the north flank of 

 the Uinta range directly opposite that studied by the writer. It was 

 described as apparently conformable to the underlying Upper Carbonif- 

 erous limestone which dips away at an angle of 52 degrees. The occur- 

 rence, as the only one observed in the Upper Coal Measure group, was 

 explained as possibly a relic of the Tertiaries or the Wyoming con- 

 glomerate and therefore belonging to the latest formations of the region. 

 The writer has not seen this case, but he is of the opinion that if the 

 conglomerate is essentially conformable to the limestone and tilted at 

 such an angle, there is much doubt about it being Wyoming conglom- 

 erate for the reason that this rock, being the latest formation of the area, 

 is seldom tilted at all. The discovery, therefore, of a Carboniferous con- 

 glomerate on the southern flank would lead one to expect the same 

 relationship in the La Motte Peak occurrence. 



Discussion 



Only at one point do the pre-Cambrian rocks project up into the great 

 quartzite formation of the Uintas enough to be seen. This was noted by 

 Powell f and by King and S. F. Emmons, J who used the name "Red 

 Creek quartzite" for the underlying formation and regarded it as Algon- 

 kian in age. The contact is considered the mark of a great erosion un- 

 conformity. 



There are no traces at any point of limestones or shales below the great 

 quartzite similar to the Silurian, Devonian, and Lower Carboniferous for- 

 mations, such as lie below the true " Weber " in the typical Wasatch section. 

 If the great quartzite is " Weber," then clearly there is no pre- Weber in 

 that particular part of the Uintas, and a break more profound than even 

 Major Powell claimed would have to be admitted ; for in that case the 

 12,000 feet of Cambrian, the 2,000 feet of Silurian, the 1,000 feet of Devo- 

 nian, and the 7,000 feet of Lower Carboniferous strata so well marked in 

 the Wasatch must be considered as wanting in the eastern Uintas. 



On the other hand if the hiatus is to be regarded as strictly local in the 

 vicinity of this baraboo of Red Creek quartzite, then one is to expect, as 

 King did, that all these enumerated formations do lie buried beneath the 

 great quartzite. 



* U. S. Geological Exploration ot the Fortieth Parallel, vol. ii, p. o24. 



t Geology of the Eastern Uinta Mountains, 1876, p. 145. 



X U. S. Geological Exploration of the Fortieth Parallel, vol. ii, pp. 198, 268-269. 



