SOME GEOLOGICAL NOTES ON COUNTRY BEHIND JERVIS BAY. 303 
almost the same dip. As the hase of the sandstone should 
here be several hundred feet higher than five miles further 
east, we have clear evidence that a great fault must have 
taken place and that the western side has been down- 
thrown at least five hundred, and possibly a thousand feet 
or more. 
It appears therefore that the Sassafras tableland is a 
‘horst’ having a great fault on its western side. From 
the direction of the facetted clifis it was seen that these 
faults have a due north and south trend. As the Currock- 
billy Range has a similar structure all the way from the 
Shoalhaven River to Milo Mountain,’ I am of the opinion 
that the whole belt lying between theClyde and the facetted 
western clifis of the range forms part of a narrow horst 
elongated in a north and south direction. The Hndrick 
River, the Clyde, and Httrema Creek rise in the heart of 
the horst. The Endrick runs in a spiral, first south, then 
west, and finally north. It has carved a huge gash in the 
western clifis of the range, and owes its size to the exist- 
ence of a basaltic neck in its valley a few miles from its 
source and a downthrow of a portion of the plateau around 
the focus of volcanic action (Kesselbriicke). The Ettrema 
having no such natural weak spots to work upon runs in a 
narrow and awful gorge. 
The basaltic neck in the Endrick valley and the basaltic 
dykes and flows around Nerriga are probably of the same 
age as the faults, perhaps a trifle later. From the clear 
facetted nature of the clifis facing Nerriga I should think 
that the formation of the Sassafras horst and the extrusion 
of the basalts cannot be older than Pliocene. 
In the auriferous country between Nerriga and the 
Shoalhaven, deep leads of a payable nature may be found 
under the basalt flows. 
+ Sugarloaf Mountain of the Tourist Bureau Map. 
