TOURTELOTTE PARK SPECIAL MAP. 89 
south, but this also passes above the surface a short distance south of the 
central part of the district, and, like the Silver fault, is not found farther 
south. Since these two faults are among the most important factors in 
determining ore deposition, it may be understood why the southern part of 
the Tourtelotte Park special district to the east of the Castle Creek fault is 
practically barren. 
The fact that the Silver system of faults has been more than anything | 
else the locus of ore deposition, shows conclusively that the faults originated 
before the mineralization. The fact that all the other systems of faults, 
both postmineral and premineral, have displaced the Silver system in pre- 
cisely the same degree as they have the adjacent strata, indicates that the 
Silver system was formed at an earlier period than the others, and it may be 
supposed that it was contemporaneous with the folding of the strata, being 
the result of the slipping of one bed over the other in the course of plication. 
Castle Creek fault — The Castle Creek fault is definitely traceable throughout 
the whole length of the Tourtelotte Park special district. Beginning at the 
north and following its outcrop south, it may be found separating the red 
Maroon sandstones from the Archean granite on the mountain side between 
Keno and Ophir gulches; southward it is distinctly shown in Ophir Gulch; 
from there it is traceable across the intervening ridge into Queens Gulch. 
It then runs southeast in the very bottom of this gulch for some distance 
until the gulch curves abruptly east, as shown on the topographical maps. 
At this point the fault does not turn with the gulch, but continues on, finally 
leaving the district close to the Surprise shaft. Through the whole distance 
the fault is shown on the surface by outcrops and underground by tunnels. 
At the point where the Castle Creek fault crosses Ophir Gulch there 
are red Maroon sandstones on its west side, with granite on the east. In 
the bottom of the gulch, however, come in narrow wedges of porphyry and 
Weber shale, rocks which underlie the Maroon sandstones on Red Moun- 
tain and the rest of the district. These wedges of porphyry and shale 
widen toward the south, until at the southern limit of the district nearly 
the entire normal thickness of Weber and of porphyry outcrops. Although 
these formations are very nearly in their normal position, their thinness at 
the northern end of their exposure and their contact phenomena show that 
they are brought into position by faults which are nearly parallel to the 
Castle Creek fault and are dependent upon it. Since the general dip of 
