198 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
in Section C, Atlas Sheet XXVIII. From this point north the two faults 
crop very close together and parallel, and probably unite soon after leaving 
the area of the map. The displacement of the porphyry sheet in the center 
of the area is due to the action of the Silver fault and not to any subse- 
quent movement. The geological features shown in the cross sections have 
been already described and do not require further mention. In studying 
the longitudinal section E, Atlas Sheet XXIX, however, it must be 
remembered that the various faults and other formation planes are cut by 
the section at varying angles, and so give varying lines of intersection, 
which are apt to mislead unless properly understood. In the center of the 
section the Clark fault is shown cuttmg the Della and Smuggler faults and 
upthrusting these faults, with the inclosing strata, to the southeast. It 
should also be noticed in this section how the Contact fault comes in at the 
extreme southern end, but soon runs into the Silver fault and disappears, 
leaving only a thin wedge of blue limestone between the dolomite and the 
shale. 
RESUME OF SMUGGLER MOUNTAIN GEOLOGY. 
The structure of Smuggler Mountain is marked by uniform steep tilt- 
ing, which has been disturbed at successive periods by faults. The first of 
these disturbing movements is represented by the Silver fault, which has 
cut out the blue limestone and part of the Leadville dolomite throughout 
the whole of the mountain, and also the thick sheet of quartz-porphyry 
which is intercalated in the Weber shales. Subsequent to the formation of 
this fault there arose a system of east-west breaks, of which the Della and 
the Alta faults are representatives. The Della fault has an east-west trend 
and a comparatively flat southerly dip, while the Alta fault, which also has 
an east-west trend, is nearly vertical. So far as can be judged from the 
phenomenon of ore deposition, however, these two faults were practically 
contemporaneous in origin. Subsequent to the formation of these faults 
there again took place a slipping along the general plane of the Silver fault, 
which locally deviated from this plane and so constituted an independent 
fault. his is called the Clark fault. The various stages in the deforma- 
tion of the rocks on Smuggler Mountain are shown in the accompanying 
diagrams (fig. 8), A representing the original condition of the beds after the 
intrusion of the porphyry and the tiltg away from the the granite axis, 
B representing the beds after the movement of the Silver fault, C showing 
