Physiograp/ii/ of Yarra, etc. 477 



For reasons that will be subsequently stated, the Senkungs- 

 feld is regarded as only relatively and not absolutely depressed. 

 The whole country was uplifted, but certain portions received 

 greater elevation than others. 



In stating the boundaries of the Croydon Senkungsfeld, no 

 reference was made to its possible extension south of Dande- 

 nong, as my personal observations in connection with this 

 paper have not extended beyond this point. 



From the known contour of the country, however, to the 

 south of Dandenong, and from the geological map accompany- 

 ing Selwyn's report of 1856 (8), the Senkungsfeld appears to 

 clearly extend in the same direction (south-westerly) through 

 the Carrum Swamp and possibly under Port Phillip. This 

 question is dealt with more fully under the section describing 

 the faults and fault-scarps. 



The Nillumbik Peneplain. 



This comprises the Yarra Plateau and the Croydon Senkungs- 

 feld, parts of the same form, but at different levels. Sufficient 

 observations have not yet been made to adequately discuss 

 the cause of the movements which have brought about these 

 different levels. 



Prof. Gregory regards the Yarra Plateau (as defined by him) 

 as a peneplain. That it is so, and also in its widened defini- 

 tion, may be seen on looking from any elevated point com- 

 manding a comprehensive view of the country. One of the 

 best of such view-points is Garden Hill," at Kangaroo Ground. 



Within the boundaries of this peneplain is included the 

 coastal plain stretching eastward and south-eastward from 

 Melbourne. This coastal plain consists of marine and fresh 

 water tertiary sands and gravels, laid down upon the denuded, 

 even surface of the silurian rocks whilst the more inland coun- 

 try was being reduced to a peneplain continuous with that on 

 which the sands and gravels were deposited. Thus the true 

 peneplain to the north merges into the coastal plain, and there 

 are thus two physiographic forms, but for convenience both 

 are grouped together as the Nillumbik Peneplain. 



