534 E. BLACKWELDER GEOLOGY OF WASATCH MOUNTAINS, UTAH 



made of closed recumbent folds here and there, generally confined to the 

 weaker members of the series and well shown in Ogden Canyon. 



The only important modification of this view seems to be that furnished 

 by Boutwell in 1907, on the basis of his studies in the Park City mining 

 district. 2^ The most important feature found there is an overthrust fault 

 of large displacement, the first to be reported from the Wasatch Moun- 

 tains. 



OVEBTHRUSTS IN THE VICINITY OF OGDEN 



In 1909 the field observations confirmed the earlier interpretation of 

 the main range from Brigham northward. That portion of it is appar- 

 ently an uninterrupted monocline with occasional little transverse faults. 

 Furthermore, there appeared to be nothing severely inconsistent with the 

 view that the west front of the range is a normal fault-scarp, as generally 

 supposed. From Willard south to Weber Eiver, however, the structure 



Figure 4.— Generalized Section of the Wasatch Range at Willard, Utah 

 Showing Algonkian slaty series overthrust on middle Cambrian limestone 



is much more complex. It may be described in general as a shingled 

 structure with overthrust slabs or wedges dipping eastward. The weaker 

 members of these slabs, especially near the overthrust planes, have been 

 bent into compressed recumbent folds and in detail are much contorted, 

 At least three of the overthrusts are large enough to deserve separate 

 description, and there are also several small thrusts which modify the 

 outcrops and structures in important details. Why these overthrusts 

 were localized near Ogden is a question which will require for solution a 

 broader acquaintance with the larger structures in northern Utah than is 

 now available. 



The greatest of the overthrusts may well be considered the master 

 structural feature of the northern part of the range (see figure 5). It 

 rises from beneath the Salt Lake sediments just north of the village of 

 Willard, crosses the lower part of Willard Canyon, and rises gradually 

 along the western buttresses until it reaches the crest of the range just 



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