452 G. F. LOUGHLIN 
Still later normal faults further complicate the structure. 
The Mississippian limestone does not appear to be over 2,000 
ft., and may be much less, above the Cambrian quartzite. The 
thickness of pre-Mississippian limestones is much less than in the 
northern Wasatch country, and greater than in the Uinta Moun- 
tains. 
Cambrian quartzite, formerly called ‘‘Ogden (Devonian),”’ 
is exposed in three domal uplifts in the American Fork—Alpine dis- 
trict. Two of the domes are faulted, and the similarity of the 
structure to that in the Cottonwood district suggests that outlying 
bosses of the granite may underlie the domes. 
Cambrian quartzite in the Provo district is exposed along two 
anticlines in line with each other, but oppositely unsymmetrical. 
A conglomerate bed in the quartzite contains impure limestone 
pebbles, indicating the existence of limestone of Cambrian or earlier 
age and an unconformity, presumably in the Lower Cambrian. 
Obscure exposures of dark limestone may represent a local bed inter- 
calated in the quartzite, but the evidence at hand is not convincing. 
In the Santaquin—Mount Nebo district the lowest exposed rocks 
are pre-Cambrian granite and schist, overlain unconformably 
by about 800 ft. of Cambrian quartzite, which is followed by 2,500 
ft. of shale and limestone, in part or wholly Cambrian, and by Mis- 
sissippian limestone. The upper Mississippian “intercalated 
series’? east of Santaquin is overlain unconformably by Eocene 
conglomerate and volcanic breccia. To the west and southwest, 
the Eocene conglomerate rests upon pre-Mississippian limestone 
and Cambrian quartzite, proving the unconformity to have beveled 
off nearly the entire Paleozoic, as well as the Mesozoic, section. 
These latter occurrences mark approximately the western limit of 
Eocene sedimentation in central Utah. 
Both overthrust and block faults are present in the Santaquin— 
Mount Nebo district. The former are for the most part obscure, 
but in each case are marked by Cambrian quartzite resting upon 
Mississippian limestone. The block faults are marked by N.-S. 
and E.-W. canyons, and are shown to be of post-Eocene age. 
