TOURTELOTTE PARK SPECIAL MAP. 99 
have steep dip, but are flat when compared with the dip of the beds on Aspen 
and Smuggler mountains, the resultant surface geology as now exposed by 
erosion is rather more complicated than anywhere else, and in many places 
presents a confused checkering. Were it not for the fact that the erosion 
of the glaciers has usually stripped these surface rocks and left them com- 
paratively bare, it would be often impossible to decipher the structure; but 
fortunately the outcrops are very numerous in some of the most compli- 
cated places. A good example of this is the geology of the hill just east of 
Copper Gulch, near the extreme northern edge of the area mapped. Pl. IV 
is a view of this hill from across Spar Gulch, and at that distance shows 
how the complicated geology is sketched out on the side of the hill as on 
a map. The hill referred to les in the foreground of the picture. The 
reader, on viewing the plate, is looking toward the east, and the left- 
hand side of the picture corresponds very nearly to the northern end of 
the Tourtelotte Park special map. By comparing the map with the plate 
the geology of the hill as shown in the picture may be understood. At the 
left-hand end of the picture there is found a normal contact of Silurian 
dolomite and Cambrian quartzite, which here strikes east and west and dips 
north. This contact is not visible on the plate, but is shown on the map. 
A short distance south of this an east-west fault brings down the dolomite, 
so that it outcrops to the south of the quartzite again. This dolomite 
occupies a portion of the left-hand side of the picture, immediately under 
the pronounced sag in the outline of the hill) A short distance south of 
this another cross fault brings up the Cambrian quartzite again. This 
quartzite 1s seen outcropping in a white streak running down the hill just 
north of the central part of the picture. Southward again there appear 
successive faults, belonging to the same east-west system; the first brings 
up the dolomite shown in the dark area in the very center of the picture; 
the next fault south brings up the quartzite, and still another has restored 
the dolomite. This last outcrop of dolomite is seen in the right-hand side 
of the picture, its lower end being obscured by the intervening spur of 
Copper Hill. To complicate this numerous system of east-west cross 
faults, there is a flat, easterly dipping fault, which apparently has a north- 
east trend, and is a sort of splinter between the Copper and Ontario faults. 
This flat fault may be noticed in the plate, running nearly horizontal, not far 
from the top of the hill. It operates so that the middle belt of dolomite is 
