76 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
mines, consisting of many nearly vertical polished and striated surfaces, 
which indicate a general zone of movement. The general effects of this 
movement were to upthrow the rocks on the east side, for in this neigh- 
borhood the dip of the Silver fault becomes much steeper than usual, on 
account of its continual upthrust. It seems probable that there are several, 
if not many, parallel slips which here diverge and there merge into one 
another, but they may be conveniently considered as a single fault, and 
in the Mollie Gibson mine, where this fault has been recognized, it has been 
called the Clark fault. The fact that the Clark fault is only slightly steeper 
than the Silver fault, which it runs very close to, and the further fact that 
the uplifting of the rocks on the east side of the Silver fault by the Clark 
fault and its dependent slips gives a slightly steeper apparent inelination to 
the Silver fault, make it difficult to follow and trace out in detail all of this 
movement. In the Gibson mine, however, it has been found that one of 
the main slips belonging to the Clark fault runs very close to the Silver 
fault, but has dolomite on both sides, thus showing that the two are not 
strictly parallel. The evidence of displacement is chiefly in the faulting 
of certain of the ore shoots inthe Mollie Gibson and in the Smuggler. These 
ore shoots have peculiar characteristics, and hence are traceable without 
ereat difficulty. The displacement of these shoots shows that there has 
been a movement toward the north on the west side of the fault of 500 or 
600 feet, combined with a vertical movement downward on the west side 
of 300 or 400 feet. Thus the actual movement was toward the north on 
the west side of the fault at an angle of 30 degrees or so with the horizontal, — 
this angle being taken on the nearly vertical plane of the fault, and the 
total displacement was 600 or 700 feet. 
North from the Smuggler mine this fault becomes still harder to trace, 
but near the Johnson tunnel the outcrops of Weber shales and of Archean 
granite seem to come suddenly very close together, so that there is no 
room, apparently, for the Parting Quartzite between the granite and the 
Silver fault. This apparent thinning of the strata at the surface, which is 
not found underground along the Silver fault, is probably due to the action 
of the Clark fault, as shown in Section A (Atlas Sheet XXVIID). Its 
throw is, however, represented as already diminished, and it probably 
grows still less toward the north. Along the top of the mountain this fault 
is hardly distinguishable from the Silver fault. In the Regent mine, 
