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GEOLOGY. — Geology and ore deposits of the Park City district, Utah. 



John Mason Boutwell, with contributions by Lester Hood 



WooLSEY. U. S. Geological Survey Professional Paper 77. Pp. 



231, with maps, views, and sections. 1912. 



The greatest geologic activity in the Wasatch Mountains took place in 



the middle portion at its junction with the great east-west Uinta Range. 



Within this area the most diverse formations are found on a prominent 



spur which extends eastward from the main divide. Extensive and 



irregular intrusion, widespread extrusion, thoro contact metamorphism, 



persistent and recurrent faulting, and glaciation have produced in a 



comparatively small area highly varied and complex results. At the 



heart of the area, in the focus of these contending factors, have been 



formed the most extensive and richest ore bodies in the range. This 



area is known as the Park City district. 



The general anticlinal structure of the Paleozoic and Mesozoic beds 

 which characterizes the Wasatch as a whole is interrupted in the Park 

 City district by a transverse (east-west) anticline or dome. Sediments 

 ranging from Cambrian to Tertiary here dip quaquaversally from a 

 series of laccolithic masses. It is noteworthy that these intrusions have 

 taken place along the line of the Uinta axis extended westward. The 

 doming by these masses athwart the general course of the Wasatch 

 naturally raises a query as to similar action in the formation of the 

 Uintas. This transverse Wasatch dome and the. Uinta dome are sepa- 

 rated topographically though not structurally by a north-south trough. 

 Into this, and thus blanketing the surface connection of these structures, 

 have flowed extensive and thick masses of andesite. The Park City 

 district is traversed diagonally by this axis. Here the sediments include 



445 



