ASPEN SPECIAL MAP. 65 
little throw, although there is a marked zone of fracture. From this null 
point southward the throw is very slight and has no constant direction. 
The tendency appears to be toward a slight downthrow to the east, as seen 
in the extreme southern part of the Durant mine, and as represented on 
Section G of the Tourtelotte Park mining map (Atlas Sheet XXIV). It 
is probable that this fault dies out entirely a short distance south of the 
null point mentioned, and is not found except in the extreme northern 
end of the area of the Tourtelotte Park special map (Atlas Sheet XIT). 
That part of the fault, however, which lies north of this null point has 
a steadily increasing downthrow on the west side. In Section C of the 
Aspen Mountain map (Atlas Sheet X XVI) this downthrow is shown to be 
only about 50 or 60 feet, while in Sections B and A, which are based on 
rough estimates, it is represented as about 400 feet. This increase in throw 
is due to the fact that the rocks on opposite sides of the fault differ in dip. 
those on the west side having a steeper northerly dip than those on the east, 
so that the formations tend to converge toward the south. 
Parallel with the main Schiller fault are several smaller breaks, which 
evidently belong to the same system, and which vary in throw in the same 
general way as does the main fault. These are distinguished in mine work- 
ings, where there are also numerous slight cross faults and fractures, but 
they can not be described in detail here. 
In mine workings it is found that ore occurs along the Schiller fault, 
apparently in place; so that this fault, like the others, originated previous 
to the period of ore deposition. 
Aspen fault— The Aspen fault is a slight break, but is important on account 
of the peculiar position which it occupies. At the junction between the 
areas of the Aspen and the Tourtelotte Park special maps the uplifting on 
Aspen Mountain reaches its maximum, and the beds begin to assume the 
flatter position and less folded structure characteristic of Tourtelotte Park; 
and the line which separates the two maps also separates two districts which 
differ materially. South of this line, in Tourtelotte Park, the Aspen Moun- 
tain syncline becomes continually shallower and finally dies out. Just to 
the north of it, however, the syncline is more pronounced than at any other 
point. Here the rocks have been so greatly folded that the eastern limb of 
the syncline becomes nearly vertical, and is locally, as shown in the Durant 
and Aspen mines, slightly overturned, so that the beds dip steeply to the 
MON XXXI 5 
