The Lake Fault Oil Gold 



which had the effect of repeating some of the beds. 

 After passing this fault, we crossed the denuded surface 

 of another overturned anticline, the rocks being met with 

 in the following order Silurian, Ordovician, Cambrian, 

 Ordovician, Silurian. 



The last named was not visible in the river-bed, but 

 occurred as a small inlier at the foot of a great escarp- 

 ment to the east of the river. 



At the foot of this escarpment, which was nearly 

 2000 feet in height, there was a sudden and complete 

 change in the nature of the rocks. The Silurian beds 

 could be seen resting on a mass of material which was 



FIG. 30. G, Gneiss ; C, Cambrian ; O, Ordovician ; S, Silurian ; T, Trias ; 



L, Lias. 



very curiously jointed and broken up into columnar 

 masses. It consisted of what appeared to be a very 

 hard and fine-grained schist. The columns lay in an 

 almost horizontal position, dipping at about 7 or 8 

 towards the south, in which direction their axes lay. 

 Their surfaces were curiously grooved and striated, in 

 fact, so regular were some of these masses that they 

 resembled stone mullions (Plate XII.). This structure 

 pointed to the existence of a fault or other dislocation 

 running along the foot of the hills, and since the plane 

 of fracture, as indicated by the lie of the mullions, was 

 nearly horizontal, it must be in the nature of a thrust- 

 plane. 



211 



