ASPEN SPECIAL MAP. 63 
tively slight. Where the fault becomes again straight and its outcrop 
parallel with that of other faults of the same system, its plane has probably 
again become vertical, or is perhaps very steeply inclined toward the east. 
Cutting across this curved line of fault outcrop, like the string of a 
bow, is a slight fault which is in more direct continuation with the main 
Saddle Rock fault than is the fault with the curved outline. The main 
displacement, however, has taken place along the most easterly plane, and 
the movement along this straighter fault is very slight, being a downthrow 
on the east side. 
The Saddle Rock fault is well shown in the Great Western, New 
York, and Monarch tunnels; also, nearer the surface, in the Late Acquisition 
incline and the Iron tunnel. From here it runs into the area of the Tourte- 
lotte Park special map (Atlas Sheet XII), where it may be traced to the 
south for a long distance. Its displacement on Aspen Mountain is seen, in 
Section C, to entail as much as 1,000 or 1,200 feet downthrow to the east. 
Toward the south the throw diminishes rapidly. This is due to the fact that 
the beds on the west side of the fault have a flatter northerly pitch than 
those on the east side, so that the formations on opposite sides of the fault 
tend to converge ‘This convergence ends in the final dying out of the fault, 
Along its whole course this fault is more or less mineralized, and the 
nature of the ore shows that it was formed in place; there is some evidence, 
however, of slight movement which has taken place subsequent to the ore 
deposition. This fault, then, like the Pride, must be considered as having 
developed almost entirely previous to the period when the ore-bearing 
solutions circulated through the rocks. 
Sarah Jane fault—'The next important fault on Aspen Mountain to the east 
of the Saddle Rock fault is one which belongs to the same system, having 
a nearly vertical dip and a north-south trend corresponding with that of the 
faults which have already been described The outcrop of this fault is to 
a great extent concealed by a covering of talus or slide material and glacial 
drift; but in a general way the line of faulting is well marked, running 
down the middle of the drift-filled basin which lies between the prominent 
ridges of Kast Aspen and West Aspen mountains, very nearly as drawn on 
the map. Its presence is indicated by the fact that the upper contact of 
porphyry and Weber shales lies at a considerable distance farther north on 
the west side of the fault than it does on the east. The syncline of Aspen 
