438 J. M. BOUTWELL 
and a great east-west zone of contact metamorphosed sediments. 
It is these metamorphosed rocks which thus hardened stand up as the 
backbone of the region, the divide between north and south drainage, 
and form the home of all the great bonanza ore bodies of the district. 
STRATIGRAPHY 
GENERAL DESCRIPTION 
The sedimentary rocks within this district are of Carboniferous 
and Triassic ages. They are divisible on paleontologic and lithologic 
evidence into five formations. The lowest (oldest) comprises the 
upper part of the Weber quartzite, which yields a Pennsylvanian 
(upper Carboniferous) fauna. Overlying this quartzite is the Park 
City formation of limestone and sandstone, the former bearing 
Pennsylvanian fossils. Next above is the unfossiliferous Woodside 
shale, which is succeeded by the Thaynes formation. The limestones 
in this formation yield a new fauna resembling both Carboniferous 
and Permian, considered of “‘Permian age.’ The highest beds 
in the district are the unfossiliferous shales constituting the lower part 
of the formation which passes upward a few miles northwest of this 
area into the Triassic sandstone, and thence into the Jurassic lime- 
stone. 
WEBER QUARTZITE 
Name.—About 30 miles due north from Park City and 1 or 2 
miles west from Croydon station, the great gray quartzite of the 
Wasatch section forms both walls of Weber Canyon. “It is from 
the characteristic occurrence of this remarkable bed of quartzite that 
the name ‘Weber quartzite’ has been given to the body” by the 
geologists of the Fortieth Parallel Survey." 
Critical paleontologic and stratigraphic studies lead to the con- 
clusion that the great quartzite of the Park City district is the strati- 
graphic equivalent of the Weber quartzite in Weber Canyon. Accord- 
ingly the name ‘‘ Weber” will be extended to apply to this formation 
in the Park City district. Locally it has been known, after the famous 
mine which lies in it, as the “Ontario” quartzite. 
1 Clarence King, Geological Exploration of the Fortieth Parallel Survey, Vol. I, 
DpawOm. 
