Physiography of Wervibee Area, ^ 253 



south, the nature of tlie junctions strongly suggests that part of 

 the mass had been faulted down. Similar observations may l:)e 

 made regarding other masses. In the case of the great horeshoe- 

 shaped Harcourt exposure, and many others, the marginal lines 

 trend north-south just as much as they do east-west. These 

 plutonics certainly do not appear to present sufficient evidence for 

 the assumption of a great continuous east-west range of moun- 

 tains. 



T. S. Hart, who has given his attention for many years to the 

 question of the origin of the Main Divide, stated in his paper 

 before the B.A.A.S., at Melbourne, 1914, (ref. 23, p. 443), that 

 ^'the actual intrusion of the granitic rocks has taken no part in 

 forming the present Divide." 



The fact that the intrusion of our pluntonics is known to have 

 been wholly palaeozoic (1 Devonian and earlier), and associated 

 with intense folding along north-south lines, would also suggest 

 that any mountain ranges associated with those plutonics were also 

 palaezoic, and with a north-south trend. 



(ii.) The Block Ranges. 



(a) The Blackwood and Lerderderg Ranges. — These ranges con- 

 stitute the whole of block A (see Plate XI. and Fig. 2), and are 

 bounded on the west and north by the Werribee River and the 

 Main Divide respectively; on the east and south are the well-defined 

 «carps of the Rowsley and Greendale faults. Either of the two 

 names given above is used to designate these ranges, the former 

 being derived from the prominent volcanic hill (Mt. Blackwood), 

 'Or from the once thriving goldfield of that name, situated in the 

 northern part of the ranges. The alternative name is due to the 

 Lerderderg River, which has carved a deep valley right through 

 the whole block from north-west to south-east. As already pointed 

 out, these ranges are almost wholly of hard, resistant, folded slates, 

 sandstones and quartzites of Ordovician age, levelled t-o a pene- 

 plain by river action, and later uplifted and dissected. The average 

 level is about 2200 feet. 



The general plan on which dissection has proceeded is set for- 

 ward as under. It must be remembered that most of these ranges 

 and streams are unsurveyed, and most of the surveys which do 

 exist are scrappy and old (as we count time in Victoria). .More 

 recently the mining area of Blackwood, and the saw-milling village 

 •of Blakeville have been surveyed, while the Commonwealth Military 



