58 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
anticlinal structure is indicated; but erosion on this mountain has removed 
all traces of the eastern part of this anticline. Farther south along this 
same axis of folding, however, a distinct anticline is traceable through a 
large part of the area shown on the Tourtelotte Park special map (Atlas 
Sheet XII), and in this area there is even another flattening of the beds 
to the east of the anticline, which indicates the existence of a slight final 
syncline resting immediately agaist the granite. 
The deformation due to folding in the southern part of the area shown 
on the Aspen special map may therefore be summed up as a local uplift, 
which had its maximum movement in Tourtelotte Park and died away 
from this point very rapidly toward the north, so that its effects are not at 
all seen on the opposite side of the Roaring Fork Valley, while on the 
south it also dies away, but much more slowly. This uplifting was 
accompanied by minor corrugations or foldings, whose axes are roughly 
parallel to the main axis of the uplift and to the Castle Creek fault. 
Most of the upward movement has actually taken place along fault 
planes, but these faults are confined to the disturbed areas and die out 
toward the north. The main series runs north and south, parallel with the 
minor foldings and with the axis of main uplift. It appears from this 
parallelism between the faulting and the uplifting that the uplifting itself 
was not due, primarily, to faulting, since the blocks of strata included 
between these north-south faults have actually undergone much bending 
previous to breaking, but that the upliftmg and the faulting are both the 
results of a single disturbing influence, and that the faulting probably took 
place mainly after the initiation of the upthrust movement. The upward 
tension evidently found relief more easily in motion along certain north- 
south vertical planes of fracture which had been developed at the same 
time as the Castle Creek fault, than in the actual bending of the rocks; 
thus it happens that the main uplifting has taken place along these 
parallel faults. 
FAULTING. 
Castle Creek fault—The Castle Creek fault outcrops in the southwestern 
corner of the district mapped, in Keno Gulch, where it is exposed im 
several short tunnels which run from the intercalated sandstones and shales 
of the upper Maroon formation eastward into the granite on the other 
