32 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213 
eastern slope, and the adjacent portion of the Uintas to the east, was 
studied en reconnaissance, and detailed stratigraphical sections in the 
nearest undisturbed areas were examined and measured. The area 
included in the general map of the Park City district was then trav- 
ersed, a considerable part of this area and also of that shown on t lie 
map of the region immediately about the mines was mapped in final 
form, and a reconnaissance study of the chief mines was conducted. 
Dining the few weeks which have elapsed since the close of these 
field studies the nature of the writer's work has not enabled him to 
obtain any significant results from mineral and rock determinations 
and the correlation of geological data from this district beyond those 
which were gained in the field. It should be understood, therefore, 
that while broad geological conclusions have been reached, and in 
some cases detailed results secured, final conclusions regarding areal 
and economic problems have not been attained. In view of this fact 
it is a matter of some doubt as to how much value may lie in these 
general statements, based upon incomplete and unstudied data. The 
following brief statement is presented, however, in the hope that it 
may be of some service in the extensive development which is now in 
active progress. Only t he general geological facts thus far determined, 
and such broad economic features as seem least likely to be altered 
by detailed underground studies, are given, and the statements are 
to be regarded as field opinions and tentative conclusions, subject to 
partial or complete modification after further field work. 
After briefly touching on the geography, history, and production 
of the district these general preliminary results will be given under 
the following headings: Under "Areal geology" will be discussed the 
stratigraphy, igneous rocks, and structure; and under "Economic 
geology " will be treated the character and occurrence of ore and 
present mining activity. 
Geography. — Park City is pleasantly situated on the eastern slope 
of the Wasatch Range, in the north-central part of Utah. It lies 
about 25 miles southeast of and 3,000 feet above Salt Lake City, 
at an elevation of 7,200 feet above sea level. In its location on the 
southern edge of a high-lying mountain prairie, at the junction of 
three great canyons which there descend to the prairie from the main 
range, this thriving mining town (population, census 1900, 3,759) has 
a position of rare commercial value. A branch line of the Rio Grande 
Western unites it by way of Parleys Park with Salt Lake City (35 
miles), and a branch line of the Union Pacific (28 miles) extends from 
the main line at Echo. It thus forms a most convenient outlet point 
for the producing mines of the district, which are all located on the 
slopes of the canyons which rise from this point southward. 
The Wasatch Range in the portion south of Salt Lake City is a 
lofty mountain unit, trending generally north and south between the 
Great Basin on the west and mountainous plateau regions on the east 
