Geology 



Several small sections occurred at intervals along 

 the escarpment, but none of them was very clear. On 

 the whole, however, they confirmed us in our opinion 

 that there was an unconformity. No really important 

 section was met with until we reached the valley of the 

 South Fork, a powerful stream which had cut a deep 

 gash in the face of the scarp, and showed the relation- 

 ship of the beds most clearly. 



At the foot of the section was a massive sandstone 

 or grit, made up of rounded and angular fragments of 

 quartz, some of which were sufficiently large to deserve 

 the name of pebbles. This, like the shales in the section 

 nearer Lyell, was seen to dip to the south-west at 20, 

 while, above it, was to be seen the soft fine-grained 

 yellow sandstone of the Permian, here reduced to a 

 thickness of 10 feet, but again succeeded conformably 

 by the limestones. 



In this section the discordance between the dip of the 

 two series of rocks was plainly visible, and the fact that 

 here the Permian rocks rested on a coarse grit, while at 

 Lyell they were upon coal-bearing shales, proves the 

 unconformability of the sequence beyond doubt. 



At the head of South Fork the Keuper Sandstone 

 was again visible, and here we also encountered the 

 continuation of the Black Point Dyke, which had now 

 changed its direction to north-east and south-west. 



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