PARK CITY MINING DISTRICT, UTAH 445 
Park City, where it swings northeast and eastward around to the 
north of the city, whence, continuing the curve, it reappears with a 
southerly strike near the base of the eastern slopes of the range. The 
continuity of this general course has been much interrupted by intru- 
sives, extrusives, and faulting. The most characteristic, and also 
the most extensive, exposures are those lying west and east of Park 
City, forming respectively Treasure Hill and Twin Knobs. 
This formation characteristically forms domar knobs and spurs 
of moderately steep slope intermediate in degree between the resistant 
quartzite below and the non-resistant shale above. No good natural 
exposures of the entire formation are known in this area. ‘The absence 
of cliff-making members, the presence of weaker members, and the 
thick growth of aspen and brush which characterize this formation, 
all contribute to cover its surface, to render it inaccessible, and to 
prevent careful examination and measurement of its members. 
Thickness.—The exposures in this area do not afford a basis for a 
close estimate of the thickness of the Park City formation. Cross- 
cuts in the Silver King and Daly West mines should, under normal 
conditions, yield the desired data, but strike-faulting in both properties 
has so complexly duplicated the succession as to render measurement 
of its thickness little more than approximation. The total thick- 
ness indicated by the Treasure Hill body is approximately 700 feet. 
The best and the only reliable section observed is the type section in 
Big Cottonwood Canyon, described above. The thickness of this 
formation at that locality measured 590 feet. 
Age and stratigraphic relations.—The age of the Park City forma- 
tion is proved, by several faunas collected from calcareous members 
in the district in Big Cottonwood Canyon and in Weber Canyon, to 
be Pennsylvanian (upper Carboniferous). Two of the type fossils 
are particularly indicative: the Bellerophon, as seen in the lower por- 
tion of the formation along the King road, in Woodside Gulch, and 
the Orbiculoidea, of common occurrence in the gray shaly limestones, 
the lower part of the formation throughout the district. The identi- 
fication of these faunas in the Cottonwood and Weber Canyon regions 
makes possible the correlation of this formation with its equivalents 
to the west and north. The association of Bellerophon sp., Productus 
cora, and Orbiculoidea sp., and the stratigraphic position of these faunas 
