Sei-peafiae Area and Rhyolites. 255 



I^nderg^-owth is very scanty, except along the river courses, 

 and where bush fires ha.ve swept the hills clear of growth, the 

 bare rubbly slate surface shows striking evidences of extremely 

 rapid gravitation under the influence of rain storms. 



(b) General Geology of the Lower Palaeozoic Area. 



The following rocks require special attention: — 



1. Serpentine and associated rocks and minerals. 



2. Sediments composed largely of serpentine detritus. 



3. Bluish grey crj-stalline and fossiliferous limestones. 



4. Black jasperoid slates with network of small quartz veins. 



5. Normal graptolite slates. 



(1) Serpentine and Associated Rocks and Minerals. 



The serpentine area consists of a narrow belt varying in width 

 from about a quarter of a mile to about two chains, and extend- 

 ing a little over three miles in length. The most northerly 

 outcrop is to be seen in the bed of the Dolodrook river, at the 

 mouth of Black-Soil Gully. Here the outcrop is about two chains 

 wide, and lies between black jasperoid slate on the north-ea,st 

 side, and black slate with bluish calcareous bands on the south- 

 west. The strike of the slate is the normal one throughout the 

 area, being approximately north-w^est. The dip is at a high 

 angle, and apparently to the north-east, but the rocks are con- 

 torted, and satisfactoiy observations could not be obtained. The 

 serpentine is much decomposed here, and it is not dear whether 

 it represents the original rock in situ-, or compacted serpentine 

 detritus, such as is found elsewhere interbedded in the lower 

 palaeozoic sediments. 



Travelling in a south-easterly direction up Black-Soil Gully 

 to its head, no more serpentine is seen till the head of the 

 gully is reached, for the underlying rocks are concealed beneath 

 a considerable thickness of black soil, full of black slate frag- 

 ments, but lai-gely derived from the sei'pentine rocks higher up. 

 The only rock outcrop noted was w^here the detritus had been 

 washed out of the bed of the gully, exposing the jasperoid slates. 

 These rocks outcrop also on either side of the valley. The 

 serpentine is again exposed in the saddle at the head of the 

 gully, known as the Monument Gap, and it can be traced thence 



