EESULTS OF DYNAMIC MOVEMENTS. 39 



theaters along- either side of the crest of the range. These dikes are some- 

 times observed cutting up tlu'ough the Archean into the overlying sedi- 

 mentary beds and then spreading out in sheets between the strata. 



Displacement. — The movement of displacement of the faults throughout 

 this area has been, with a few unimportant exceptions, an upthroAv to the 

 east. The maximum movement of any one fault is that of the Mosquito 

 fault, at the northern edge of the map, which is about five thousand feet. 

 In general the movement of the individual faults decreases to the south- 

 ward until they gradually pass into folds and it becomes nil. The aggre- 

 gate amount of displacement, however, summed up along east and west 

 sections, increases toward the middle of the region, where the development 

 of sheets of eruptive rocks is greatest, and decreases as these become less 

 important; thus, as above mentioned, the displacement at the northern edge 

 of the map is about five thousand feet. In the middle region, where the 

 faults are numerous, the aggregate displaceiuent is 8,000 to 10,000 feet, 

 and across Sheep Mountain and Weston Peak it has decreased to 3,500 feet, 

 becoming nothing at all just beyond the southern limits of the map. 



Volcanic rocks. — Thus far Only the earlier eruptive rocks have been men- 

 tioned, for the reason that they alone were involved in the folding and 

 faulting. Later eruptions of Tertiary volcanic rocks have taken place since 

 the folding, and probably after erosion had done the greater part of its work 

 in the removal of Paleozoic sediments. These eruptions within the area 

 of the map consisted of rhyolitic lavas, of which the two most prominent 

 outpourings were at the extremities of this area, the one forming the mass 

 of Chalk Mountain north of the east fork of the Arkansas and some smaller 

 bodies to the east of Fremont's pass, the other that of Black Hill, on the 

 extreme southeastern edge of the area in Sovith Park. Besides these there 

 are small bodies in the granite and in the Cambrian quartzite at the west foot 

 of Empire Plill. A few miles south of the southern limit of the map is an 

 important volcanic eruption of andesitic lava, cutting across both the Archean 

 and the Paleozoic beds, which forms the high mass of Bufi^alo Peaks. These 

 later eruptions, however, so far as can be determined, had no influence upon 

 the ore deposits of the region. 



