WEBER QUARTZITE 533 



the Weber qiiartzite is easily recognized, but seems to be reduced to a 

 thickness of 1,200 to 1,500 feet. The exact contact between the quartzite 

 and the Park City formation is unfortunately covered with soil. At 

 about the proper horizon, however, there are poor exposures of a soft, 

 white, fine-grained sandstone like that in AYeber Canyon, and it likewise 

 contains angular fragments of gray quartzite and chert. 



The observable facts with reference to this contact leave much to be 

 desired, and no attempt is made here to interpret fully the conditions 

 under which it was made. Certain things, however, seem to be clear : 

 (ft) The Weber quartzite is limited above by an irregular eroded surface, 

 which is not exactly parallel to the bedding; (&) it was subject to disin- 

 tegration, and (c) not merely one, but a variety of beds in the formation 

 were exposed, as is shown by the large amount of chert as well as quartzite 

 in the breccia. On the whole, the evidence for the existence of an uncon- 

 formity at this horizon seems to be conclusive. 



The importance of the unconformity is uncertain. If the Weber 

 quartzite is a formation of only local extent, and if some of the more 

 calcareous beds farther north were deposited contemporaneously, then 

 the observed unconformity may in fact be due to a slight erosion of the 

 surface of the formation and should represent but a brief land interval. 

 If, however, the Weber quartzite 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 Penn- 

 sylvanian period, then this interval must have been relatively long. It is 

 significant in this connection that the fragments 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. For the present the problem must remain in 

 this doubtful state, but careful observations at as many points as possible, 

 within a radius of 100 miles or more, should soon decide it. 



Structure 

 previous studies 



The interpretation of Wasatch structure which has prevailed until 

 recent years is that derived from the work of the Survey of the 40th 

 ParalleP* According to this view, the main range is a monocline dipping 

 eastward and cut off on the west by a profound normal or gravity fault. 

 Small transverse normal faults with a general east-west trend served to 

 account for sudden shiftings of outcrops. In addition, mention was 



2* Op. cit., vol. il, sections 3 and 4. 



XXXVIII — Bull. Geol. Soc. Am., Vol. 21, 1909 



