HINTZE, GEOLOGY OF WASATCH MOUNTAINS, UTAH 123 



and should represent but a brief land interval. If, however, the Weber quart- 

 zite was once far more extensive than now, and if it has been removed from 

 the northern part of the Wasatch region, and elsewhere reduced to a varying 

 thickness by erosion within the Pennsylvanian period, then the interval must 

 have been relatively long. It is significant in this connection, that the frag- 

 ments of quartzite in the basal breccia were quartzite, rather than sandstone, 

 when broken from the parent ledge, during the erosion interval, as is shown 

 by the preservation of sharp corners and edges." 



The exact amount of time represented, if we grant the presence of an 

 unconformity between the Weber quartzite and the Park City formation, 

 can only be decided by finding out the ages of these two members. If the 

 Park City formation is Pennsylvanian in age and the Weber quartzite is 

 late Pennsylvanian, as the Oquirrh mountain sections indicate, then the 

 interval must be short and relatively unimportant and cannot explain the 

 great variation in thickness of the Weber and its total disappearance in 

 sections not far distant from its type locality. If, on the other hand, the 

 Park City formation is made Permian in age and the Weber quartzite 

 early Pennsylvanian, then a great hiatus must exist between the two for- 

 mations. Such a one should be well marked, and we should expect it to 

 be especially easy to recognize where the Weber is thinnest by its most 

 extensive erosion. The presence of a basal conglomerate with well- 

 rounded quartzite pebbles should be expected within short distances of 

 the present occurrences of the parent body. Again, if the Park City, 

 formation is Permian in age and the Weber late Pennsylvanian, a small 

 hiatus may exist between the two, such as has been described by Black- 

 welder. It may be safely assumed that the Park City beds are late Penn- 

 sylvanian or early Permian, and in view of the high position of the Weber 

 quartzite in the Oquirrh mountain sections, it seems clear that no great 

 erosion interval exists between these two formations. The thinning of 

 the Weber is more easily accounted for by overlap, as it was undoubtedly 

 laid down on a surface that had been long exposed to erosion. 



PARK CITY AND LATER FORMATIONS 



The Park City formation has been named from the Park City mining 

 district within which it carries bonanza ore bodies. No good exposures 

 are known, however, from the Park City area, and within the area 

 specially studied for this report, the formation does not occur. It is of 

 interest, nevertheless, to give the characters of this formation some con- 

 sideration from the widespread occurrence of this member in the central 

 Wasatch and northward. 



