Physiography of Werrihee Area. 225- 



along the slope, and so remained. This is the portion of the scarp 

 most difficult to read. 



Where the glacial sandstones of the southern part of Bald HilE 

 remain on the up-throw side of the fault (see Fig. 10), they show- 

 excellent exposures in plan and section of these beds, with a steep 

 dip easterly towards the down-throw side of the Rowsley Fault. 

 This fact, considered in conjunction with the already mentioned 

 tilting of the tertiary series (ordinarily level-bedded), suggests 

 that where the Rowsley Fault intersected the younger, more varied, 

 less compacted, and more level-bedded rocks of the " Ballan sunk- 

 land," it partook more of the nature of a monocline. This is in 

 sharp contrast to the abrupt break that marks the fault where it 

 cuts through the harder folded Ordovician slates and sandstones. 



North of Bacchus Marsh, the great valleys of the Lerderderg and 

 the Korkuperrimul, with their thick alluvial terraces, obliterate 

 the actual fault, which runs about a mile up the Korkuperrimul and 

 then passes to the eastward of Bald Hill, continuing as the east- 

 tern boundary of the Lerderderg ranges. Near the point where the 

 Lerderderg emerges from the Ranges, a fault coming from the north- 

 west cuts across the scarp, and to the north of that we once more 

 get a great resistant block of high Ordovician (Lerderderg Ranges) 

 to the west, with less elevated Ordovician, glacials and tertiaries to 

 the east. Thence the country is very difficult of access, and while 

 the fault probably continues and dies out in the neighbourhood 

 of Bullengarook, the evidence for this is wholly physiographic, and 

 was not closely investigated. 



We may conclude then that the Rowsley or Bacchus Marsh scarp 

 is due to a fault, is most probably post-newer basaltic in age, is 

 certainly so in part, has an average displacement of about 800 

 feet, and is at least thirty miles in length, trending about 15 to 20 

 degrees E. of north, and bounding the eastern faces of the Bris- 

 bane Ranges, the " Ballan Plateau," and the Lerderderg and 

 Blackwood Ranges (see Fig. 5). Since the movement was probably 

 one of uplift of the higher blocks (A, B and C), rather than a let- 

 down of the lower block (E), it may be that it was contemporaneous 

 with those uplifts that are classified as occurring in the " Kosciusko 

 Epoch. "- 



(ii.) The Greendale Fault. — ^^The second important physiographic 

 feature of the area is what we may refer to asi the Greendale Scarp, 

 forming the boundary between the blocks A and B (Fig. 2), and 

 being the southern boundary of the great dissected block of Ordo- 

 vician (Blackwood and Lerderderg Ranges), which stretches from' 



