TOURTELOTTE PARK SPECIAL MAP. oi 
true fault contacts. These dependent faults, however, are active only in 
the immediate vicinity of the Castle Creek fault, so that when the normal 
dip of the beds brings the porphyry and the Weber shales to the surface, 
and the divergence between the strike of the beds and the trend of the 
Castle Creek fault causes a separation of these beds from the fault, their 
thickness seems to be normal, and not increased or diminished by any 
dependent faulting. 
Since the elevation of the hills is greater at the southern end of the 
Castle Creek fault as exposed on the Tourtelotte Park special map than it 
is on the north end, and since in spite of this fact the beds which are 
exposed on the western side of this fault belong to horizons growing succes- 
sively lower southward, it follows that there has been a marked elevation 
of the beds in the southern part compared with those farther north. On 
the east side of the Castle Creek fault, however, the reverse is true; for 
southward are successively higher and higher formations. In the northern 
part of the area mapped, for example, there lies on the east side of the 
Castle Creek fault a great body of granite. On going south along the 
fault, one passes in the neighborhood of Ophir Gulch from granite into 
the overlying quartzite, which here comes into contact at the surface with 
an uplifted wedge of Weber shales; farther south one passes from quartzite 
into Silurian dolomite, which in the neighborhood of the Dubuque tunnel 
outcrops on the eastern side of the fault, abutting against shale or quartz- 
porphyry on the western side. The more recent Butte fault has so operated 
that south of hero the Cambrian quartzite again outcrops along the east 
side of the fault for some distance. During most of the distance that the 
Castle Creek fault runs in Queens Gulch it has this quartzite on the east, 
with the Weber shale becoming very thick on the west. Near the head 
of Queens Gulch the rocks on the eastern side of the fault change from 
Cambrian quartzite back into Silurian dolomite; farther up the dolomite 
gives way to diorite-porphyry, which in turn is replaced by the dolomite 
belonging to the Leadville formation, so that at the limit of the mapped 
area on the south the fault separates Leadville dolomite from quartz- 
porphyry. This succession of beds on the east side of the fault» shows that 
there has been no such tilting as occurred on the west side. If any tilting 
has oceurred it has been exactly the reverse, and the southern part of the dis- 
trict has undergone a slight depression as compared with the northern part. 
