Physiography of Yarra, etc. 493 



The Age of the Nillumbik Peneplain. 



Dr. Hall (14, p. 64) inclines to the opinion that the tertiary- 

 sands and gravels of Camberwell and adjacent districts are 

 of fresh water origin, and of the same age as the marine beds 

 at Beaumaris, that is, Kalimnan, and with this view the writer 

 agrees. 



These fresh water beds rest upon the surface of the Nillum- 

 bik Peneplain, and therefore would be deposited in the main 

 after that portion of the peneplain on which ih.Qj are deposited 

 had been formed ; it follows that the period of planation of the 

 peneplain as a whole was during or prior to Kalimnan times. 



The uplift of the peneplain probably dates therefore from 

 late Kalimnan time or its close, and it has continued apparently 

 to very recent times, with vibrations (to use a graphic term 

 employed by Mr. E. C. Andrews) at the south-western end of 

 the peneplain. 



The Barwonian and Kalimnan series of rocks are generally 

 regarded as of eocene and miocene age respectively. Recently 

 the miocene age for the Jan Jukian, a subdivision of the Bar- 

 wonian, has received support from an examination of certain 

 groups of fossils by Mr. F. Chapman (15, p. 311). 



The Kalimnan, which are admitted by all authorities to be 

 younger than the Jan Jukian, will, if Mr. Chapman's views as 

 to the age of the latter ultimately prevail, have to be removed 

 to a later period, presumably the older pliocene. 



I cannot express any opinion as to the ages of the rocks in 

 question, from a palaeontological standpoint, but I would point 

 out that from a physiographic point of view, the more recent 

 age would be more acceptable ; as, assuming that the Nilliun- 

 bik Peneplain was completed during Kalimnan times and up- 

 lift then commenced, the erosion by the Yarra seems little 

 advanced for a stream working from the close of the miocene 

 time, especially when the erosion of the lower Yarra since 

 newer basalt time is considered. 



No definite statement however can be made on the point, 

 and the fossil evidence will of course have ultimately to deter- 

 mine the question, but where the palaeontology is conflicting 

 or interpreted by different authorities in different ways, then it 



