Vol. 4] Lawson. — The Robinson Mining District. 355 



here is downward on the south side of the fault and its minimum 

 amount is about 100 feet. This fault curves somewhat on its 

 strike and if continued for about half a mile beyond the point 

 where the dislocation is apparent on the northeast face of the 

 Quarry Hill, it would converge upon the White Hill fault in 

 the vicinity of Copper Flat. In attempting to follow the fault 

 to this intersection, it was found that the fault appears to fade 

 out and no dislocation was observed of the west boundary of 

 the Quarry Hill area of rhyolite. Followed to the eastward the 

 fault is observable in the dislocation of the quartz blout near 

 the grade up from Ocher Valley to the Ruth Mine. The trend 

 of the fault from this point would be toward the Ruth Mine 

 and it is possible that the precipitous bluffs which rise above 

 the mine are in some way an expression of this fault, but no 

 dislocation of the rocks could be here detected. Beyond the 

 mine, however, there is an obscure line of dislocation of the 

 quartz blout, porphyry, and limestone, extending from the north- 

 east corner of the Ruth claim to the east end line of the Kimbley 

 claim. 



The remarkable geomorphic character of Lane Valley and 

 the -stratigraphic relations of the formations on either side of 

 the valley suggest that the course of the valley has been deter- 

 mined by a fault; but as the valley is deeply filled now with 

 alluvium, the nature of the fault, if such there be, is obscure 

 and difficult to decipher. In the lower part of Lane Valley be- 

 yond the limits of the map, there is an important fault trans- 

 verse to the trend of the valley, the dislocation of the strata 

 being observable on the precipitous north side of the valley. The 

 alluviation of Lane Valley is probably due to a disturbance of 

 the drainage caused by this dislocation. Below the flat-bottomed 

 alluviated portion of the valley, the drainage is through a rather 

 steep grade, rocky gorge. 



Besides these more important faults, a number of minor dis- 

 locations were observed, but they could not be traced for more 

 than short distances and they do not appear to be factors in the 

 structure which call for more than the briefest mention. One 

 of these is on the east flank of Rib Hill ; a second crosses a gulch 

 about 500 yards west of the head of Lane Valley with a north 



