332 THE LAKE GEORGE SENKUNGSFELD, 



of rounded quartz. Returning to the lake-bed itself, just at the 

 mouth of Grove Creek, a well has been sunk thirty feet into the 

 silt. The dump consists largely of pipeclay identical in appear- 

 ance with that from the shafts nea^dy 300 feet higher on the 

 elevated alluvials. I was informed that boulders of a similar 

 nature to those found at Diamond Hill were removed, but the 

 clay had covered over the early dumpings. 



We have no dat ,ufficient to estimate the length and drop of 

 this fault. It extends for more than twenty miles from Collector 

 to Bungendore. Beyor ' the latter, as the Molonglo has cut 

 through the scarp (see page 334), the fault was not so extensive, or 

 the movement may have developed merely as a fold. It is a 

 matter of great difficulty to detect Tertiary foldings superimposed 

 on Palaeozoic anticlines, but the river-development would seem to 

 suggest that such faulting or folding has occurred near Molonglo. 

 North of Molonglo River the streams flowing from the west are 

 obsequent, and flow to the lake with short steep beds in narrow 

 gorges. Here, undoubtedl}^, a fault on a large scale has taken 

 place, and totally altered t'le drainage system, the tributaries of 

 *'Lake George River" being hetrunked much as are those flowing 

 into Port Phillip (Gregory). 



Since the river-gravels at Grove Creek are ele\ated 270 feet 

 above the lake-bed, we require a minimum dvo^ of 270 feet. The 

 well sunk in the silt adds 30 feet. This well by no means reached 

 rock bottom. There is an opinion, shared by the expert local 

 engineer, Mr. Glover, that the silt is 100 or 200 feet deep on the 

 western shore of the Lake. The lesser figure agrees closely with 

 the slope of the line joining the Grove Creek and Diamond Hill 

 gravels (see Fig.l). Hence it seems legitimate to place the 

 fault drop at about 370 feet at this locality (Geary's Gap). 



Comparing this with the Kurrajong Fault, it would appear to 

 be on a somewhat similar scale. The fault, as described by 

 Professor David,* extends about twenty miles, and has a drop of 



* " An important Geological Fault at Kurrajong Heights, N. S. Wales." 

 Journ. Proe. Koy. Soc. N. S. Wales, 1902. 



