116 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
run from top to bottom of the section, and these are the faults which run 
across both blocks, traversing the Copper fault without any apparent 
break. This section illustrates well the great difference in persistence of 
these east-west cross breaks. 
The Butte fault has a slight downthrow to the south, and south of 
this are a great number of parallel east-west southerly dipping faults. 
The beds along the top of the hill have a slight northerly pitch, so that 
lower beds tend to outcrop successively toward the south; but these 
parallel faults have a uniform slight downthrow to the south, so that the 
outcropping horizon, which is about at the Parting Quartzite, is kept very 
nearly the same. The southernmost of these faults, however, appears to 
differ from the rest in having a reversed upthrow to the south. 
In this section the change of position in the diorite, as illustrated from 
place to place in the east-west sections, may be continually followed. At 
the southern end of the section the diorite occupies the position of the 
Parting Quartzite, between the Silurian dolomite and that of the Carbon- 
iferous, and it appears here in its maximum thickness, so far as the present 
mapping goes. Toward the north it cuts very gradually down across the 
beds until about the center of the section, where it cuts down more rapidly 
and enters the Cambrian quartzite. In this it continues, gradually getting 
deeper, as far as the northern limit of the mapped area, where it is a very 
thin sheet, lying close to the granite. A short distance farther north, on 
Aspen Mountain, the diorite disappears. 
section!—In this section granite outcrops at the north end. Farther 
south is a series of faults which belong to the east-west system, and which 
have the effect of thrusting down the blocks to the north. 
Between this faulted area and the place where the section cuts the 
Castle Creek fault there is a comparatively undisturbed portion, in which 
the beds lie nearly flat, with only slight undulations along the strike. 
Thus the Cambrian quartzite is exposed in outcrop, with the Silurian 
dolomite overlying it, on the ridge cut by the section. The Castle Creek 
fault is cut obliquely, as well as the two main dependent faults, the Annie 
and the Dubuque. The east-west fault, which has been called the Butte, 
has cut and faulted the Castle Creek fault, being of later origin; and as 
the section cuts the formations near the intersection of all these faults, the 
structure shown is complicated. 
