Physiography of Werrihee Area. 



2;37 



-and form the boundary between the older basalt (black clayey soil) 

 .and the glacial sandstones (light sandy soil). 



It was thought advisable to closely investigate the faulting of this 

 ^■rea, as typical of the small faults that are believed to abound 

 throughout the whole of the Ballan Sunkland. Both the geology 

 and physiography proved to be of much interest. Fig. 10 shows 

 the particular area in some detail, with 50 foot contours. Bald 

 Hill itself forms the central portion' of this plan, running from the 

 north to the south. The steep bounding valley on the western side 

 is that of the Korkuperrimul Creek, while the wider valley, partly 

 shown on the east, is that of the Lerderderg River. At least four 

 faults occur in this small area, and their influence is very clear 

 both in the geology and the topography. These faults are marked 

 by the letters A, B, C, and D. The fault marked A has been 

 already described as part of the Greendale Fault; B is portion of 

 the Rowsley Fault; C and D are two smaller faults that we may 

 call the ''Ball Hill Faults." 



Fig. 10.— Contour plan of Bald Hill, near Bacchus Marsh. Fifty feet 

 vertical intervals. A, B, C, D indicate faults referred to in 

 Section Vlllb. 



Geologically, there faults fornx almost exact boundaries. For 

 instance, the triangular patch in the north, bounded by faults A 

 .and B, is Ordovician — portion of the high Lerderderg Ranges. 



