Fhysiography of Werrihee Area, 211 



Jas. Stirling (ref. 51), Avriting thirty years ago, on an area in 

 our Eastern Highlands, says: ''That a vast tableland existed in 

 Miocene times, stretching from Mt. Buller to Mt. Kosciusko, and of 

 which the Omeo plains and Maneroo tablelands are visible rem- 

 nants, seems to be abundantly proved. Powerful erosion has sub- 

 sequently excavated deep valleys, which now break up these once 

 extensive tablelands." Mr. Stirling was aware of the gradual up- 

 rise of the land as a factor in deepening the rivers, but he wrote 

 of these facts at a time when our present physiographic termin- 

 ology was scarcely known. 



The question appears to gain in complexity as one studies the 

 individual viewpoints of other investigators. For reasons already 

 stated, the writer can see definite proof of only one great pene- 

 planation in this State. Two or three scattered monadnocks, of 

 .somewhat similar height, can hardly be called in as evidence of a 

 prior planation. They would perhaps owe theii- existence to 

 superior resistance, and if plutonic, may not even have been un- 

 'Covered at the conclusion of a previousi base-levelling of the area. 



Various writers referred to have demonstrated, and all agreed, 

 that uplift was very gradual. Undoubtedly also there w^ere periods 

 of no movement, and in some localities periods of depression. Jas. 

 Stirling (ref. 51) refeis to thick terrace alluvials on the sides of 

 the Tambo, high above the present level of the river; these bear 

 witness to a more or less sustained period of still-stand, with conse- 

 quent deposition. Similar terraces occur in the Goulburn, and the 

 writer has examined relics of such terraces high up along the 

 valley of the Lerderderg, where three series occur. Depression 

 must also have occurred in parts of the State, as pointed out by D. 

 J. Mahony (ref. 39, p. 377), in order to allow of the deposition of 

 our marine Kainozoics. The great depth of tertiaries in the Sor- 

 rento bore (1696 feet) and the still more unexpected result at Port- 

 land, where 2265 feet of the tertiaries were penetrated, without 

 reaching the bottom of the series, (ref. 40), prove extensive kaino- 

 zoic depression. Such depressions were to some extent local, and 

 occurred in conjunction Avith the progressive uplift of the neigh- 

 bouring highlands. 



(d) Conclusions. — Regarding the completion of peneplanation of 

 a. large resistant rock area as an event of at least a similar order 

 of magnitude, in time, as a geological period of sedimentation, and 

 possibly of rarer occurrence, the writer's present conclusion is that 

 .the peneplain represented by the present level crests of our Vic- 



