202 Charles Fenner : 



VIM — Dominant Physiographic Features. 



Before eiiteriii<:: upon tlie detailed description of hill and 

 valley, Ave may first set out the three dominant tectonic occurrences- 

 which have governed and decided the present day physiography of 

 this area, as well as of a large part of the State. 



Firstly, a great " still-stand,'' during which a highly complete 

 stage of peneplanation was reached. 



Secondly, a widespread general uplift of this peneplaned area, 

 gradual and differential. The differentially raised blocks separated 

 along fairly sharp and straight lines, giving us fault scarps which 

 still largely control the physiography. 



Thirdly, after initiation of a new pliysiogiaphic cycle, based 

 largely no doubt on the older features of the peneplain, we had a 

 great volcania period Avhen the newer basalt sheets wiped out many 

 of the old river systems. A second period of faulting, with dif- 

 ferential uplift, occurred. New river systems were initiated, and 

 subsequent erosion has led to the! formation of the varied series of 

 hills and valleys, Avhose present day appearance now occupies our 

 attention. 



Eacli one of these three great features is important enough to- 

 warrant separate consideration, and since they are all excellently 

 exemplified in the Werribee River area, Ave shall proceed to discuss 

 them under the folloAving heads : — 



(a) The PenepUiin, its date of completion. 



(b) The Faulting, its age and effects. 



(c) The NeAver Volcanic Sheet, and its effects. 



Other important happenings, such as the '* older " period of 

 vulcanicity, and the period of fluviatile or lacustrine deposition, 

 are referred to in Section VII. and later sections. While these, too, 

 played important parts in the production of the present physio- 

 graphic features, the three above-mentioned happenings A\'ere found 

 to be the dominant factors, and a separate section' is therefore 

 devoted to them. 



(a) 7^he Peiieplain, its date of comphtio?! . 



(i.) Introductory. — The Avriter enters on tliis (juestion Avith the 

 greatest tiepidation, recognising tlie number and variety of con- 

 ceptions that have already been published on the matter, and the 

 difficult and sometimes contradictory nature of much of the evidence 

 on Avhich a decision must be based. In consideration, hoAvever, 

 of close observation and critical examination of Avhat appear to him 

 to be fundamental points, he inakes bold to advance the conclusions- 



