78 BULLETIN OF THE 



manifest that they furnish us with dissections of small fractures similar 

 to the greater cues that control the structure of the region. The quarry 

 could not have been placed more advantageously for geological results. 



The faults of the region have been found to have their heave on the 

 east ; if the dislocations revealed by the breccias belong to the same 

 family as those that dominate the topography, we should expect them 

 to present the same relative movements. The only opportunity to test 

 this is found in the western part of the quarry, where the surface of 

 contact between the upper and lower sheets affords a recognizable layer 

 for identification on the two sides of the fracture. The displacement 

 thus determined is of small measure, about eight or ten feet, but it 

 is of the same order as the larger ones already determined, having its 

 iiplift on the eastern side. 



Four fault breccias may be found in the quarry ; their average bear- 

 ing is N. 63° E., their hade averages 71° with much constancy. Near 

 the eastern foot of the quarry a broad breccia is seen much weathered ; 

 it has probably been but little stripped of t*he cover that it had before 

 the quarry was opened. The little hollow, along which the branch track 

 is laid from the Consolidated Road, undoubtedly marks the site of the 

 Great Fault, and if opened would be of much geological interest. Walk- 

 ing across the hollow to the sandstones with barytes veins on the 

 eastern side, we have stepped down almost two thousand feet, for the 

 Great Fault which sets Lamentation ^Mountain over a mile back from this 

 portion of the main sheet can hardly have a less throw than that 

 amount. A transverse section of the quarry would, if fully worked 

 out, probably appear as in Fig. 12, and the occurrence of step faults as 

 there indicated goes far to explain the reason for the easy opening of 

 other fault lines into gaps such as characterize the region. 



It may be noted that fault breccias have been found in several other 

 localities, and that they accord in strike and dip with the system here 

 described. Percival called them " clay dikes," and examples will be 

 mentioned below. 



An instructive view is opened by climbing to the top of the quarry 

 bluff by its western slope. A northeast valley (2), Fig. 11, separates 

 the quarry ridge from other similar but higher ridges (3), and indicates 

 a fault. Isolated ledges in the valley suggest chips of trap broken from 

 the adjoining blocks. The quarry ridge therefore belongs to a very 

 narrow block, and its anterior trap can only be found by keeping care- 

 fully within the limits of its enclosing faults. Walking southwestward, 

 a small trap outcrop (4) is found in the roadway west of the Fair 



