BETWEEN BA.LL MOUNTAIN AND WESTON FAULTS. 219 



South slope of Ball Mountain. — On the soutli slope of the Ball Mountain Ridge, 

 towards Iowa gulch, the White Limestone is also split into three distinct 

 sheets by intrusive masses of White Porpli}uy. They might perhaps be 

 considered to be simply caught up and included in the porphyry body. 

 One or more of these sheets can be traced on the upper slope of Long 

 and Derry Ridge, in tlie angle between Ball Mountain and Mosquito faults. 

 South of the crest of Ball Mountain the Emma tunnel (C-10) is run on 

 the contact of White Porphjay and White Limestone, following some iron- 

 stained vein material. West of this and adjoining the fault, the Lower 

 Quartzite outcrops under the White Limestone, dipping at an angle of 50° 

 to the east. Another portion of the Lower Quartzite is found adjoining the 

 fault on the shoulder south of Ball Mountain, and in the bed of Iowa gulch 

 erosion has exposed the full thickness of the Lower Quartzite, with a small 

 area of Archean rocks next to the fault on the east, the rpiartzite dipping 

 east at an angle of 18°. 



The distribution of the Wiiite Porphyry bodies in this area is rather 

 exceptional, as they are principally developed in the lower horizons, form- 

 ing several sheets within the Lower Quartzite and White Limestone, while 

 tlie bed above the Blue Limestone is comparatively thin, and at one ))oint 

 entirely wanting. It might be inferred from this that near here is one or 

 more of its vents or points where it has been intruded through the Archean 

 into the overlying Paleozoic beds. 



AREA BETWEEN BALL MOUNTAIN AND WESTON FAULTS. 



This area presents a still more complicated structure than the one just 

 described, owing, first, to the existence of a well-defined anticlinal or qua- 

 quaversal fold, the South Evans anticline ; second, to the disturbance pro- 

 duced by the Iowa gulch and Colorado Prince cross-faults, which run ti-ans- 

 versely across the area ; third, to the peculiar movement of displacement of 

 the Weston fault, which has the normal upthrow to the east at its northern 

 and southern extremities, but in the intermediate region has partly a reversed 

 throw or to the westward, and in one portion no displacement at all ; and, 

 fourth, to the branchiuo- of the Weston fault at its southern end, bv which 



