36 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
of the transverse folds, which are now buried beneath the valley plains, while the 
detailed structure has been still further complicated by a system of transverse 
faulting. * * *a 
That portion of the range which is included between Utah Lake and Emigra- 
tion Canyon forms a geological whole, consisting of a series of sedimentary for- 
mations, flexed around a body of * * * granite. * * * Horizons from the 
Cambrian up to the Middle Coal Measures are at different points in contact with 
the granite body. * * * Of the immense arch which once covered this body 
the western half has been faulted down, while the top of the arch, with its thick- 
ness of 30.000 feet of rock masses, has been broken up and worn away by 
atmospheric agencies. b 
The composite crystalline mass comprising the granite of Lone 
Peak and Little Cottonwood Canyon, the granodiorite at the heads of 
Big and Little Cottonwood canyons, American Fork, and Snake Creek 
(Provo), and the diorite at the heads of Big Cottonwood, East Can- 
yon, and Snake Creek, with its extensions northeast through the 
Park City district, in the form of dikes, is the dominant factor in the 
greater geological structure of the middle Wasatch. The ages and 
the relationships of these great intrusive masses have not yet been 
completely established. In a broad structural sense the bodies may 
be regarded as forming an immense composite laccolith. In this light 
the striking obliteration of the normal anticlinal structure of the 
Wasatch, and the marked quaquaversal dip in this immediate section, 
become significant. The Algonkian on the west, the Cambrian to 
Mesozoic on the north, the Carboniferous on the east, and the Cam- 
brian to Carboniferous on the south, each dipping away from this 
intrusive center, are seen to be the flanks of a great laccolithic dome. 
This main structural feature, supported by the evidence afforded by 
the intrusive character of the contact between the crystallines and 
the elastics, by the marmorization and deformation of the adjacent 
country rock, and by the occurrence of an unusually complete series 
of typical contact-metamorphic minerals, is conclusive as to the part 
this intrusive mass has played in the history of the region. 
Stratigraphy of the district. — The stratigraphical series in the imme- 
diate vicinity of Park City has been so modified by faulting, intru- 
sion, and metamorphism that no reliable extended section could there 
be found. One on the north side of Big Cottonwood Canyon, between 
1 and 2 miles west of Park City, was studied in detail. As several 
requests have been received for information regarding this section, 
for the purpose of establishing the relative position of the ore-bearing 
members in this mining district, a general summary of that section 
is given. The sedimentary series includes three chief rock types — 
quartzite, limestone with calcareous sandstone, and shale. In gen- 
eral, the succession (from the older to the younger), the thickness, 
« Emmons, S. F., U. S. Geo!. Expl. 40tb Par., Vol. II, p. 341. 
&Ibid., pp. 353-355. 
