Physiography oj Werribee Area. 199 



■Oreendale. The glacial deposits are estimated to have a maximum 

 thickness of over 2000 feet (lef. 12, p. 269), and their base is 

 exposed in many places. They are rarely stratified, are well 

 jointed, and are intersected by numerous dykes, now largely decom- 

 posed. These dykes may be seen typically at the North quarry in 

 'Oreendale, along Dales' Creek, and in the bye-wash cutting at 

 Pyke's Creek reservoir. 



The " glacial, beds " are much less resistant than the Ordovician 

 rocks on which they rest. Almost all trace of these has been denuded 

 from the higher peneplaned surface of Block A, but the finding of 

 undoubted large glaciated pebbles on the caps of the ridges north 

 of Greendale, proves the previous existence of such deposits there. 

 Mr. C. C. Biittlebank, has also kindly taken the writer to various 

 small patches of undoubted glacial conglomerate, each a few square 

 yards in extent, on the topmost ridges of the Lerderderg Ranges, 

 about 1000 feet above the bed of the Lerderderg River (where it 

 •enters on the flats). It would appear from the evidence in this 

 iirea that the glacial only survived the peneplanation where it had 

 been faulted down, or else persisted, as stated above, in small 

 patches, probably in old valley bottoms in the Ordovician. 



(d) Older Bascdfic lava flows. — This rock is generally described 

 as of lower to middle tertiary in age. Messrs. Hall and Pritchard, 

 believed it to be " Eocene," but other geologists place it higher in 

 the series, approximately '' Miocene." The rock is usually a dense 

 black basalt, and is mainly preserved in this area by faulting 

 (Greendale and Bacchus Marsh), ^or faulting and warping (Maude). 

 The question of the age of these lavas is briefly discussed in later 

 portions of this paper. 



Where it outcrops, it forms well rounded hills (Fig. 20), and 

 provides excellent soils, which add much to the fertility of the 

 localities mentioned. Beds of tuft', sometimes a bright red, occur 

 in the series, and are to be well seen where thd Myrniong-Greendale 

 road crosses the Korobeit Creek. There appear to have been 

 numerous flows, which in places may be seen tilted at various 

 angles, especially along the right bank of the Lower Korkuper- 

 rimul, and at a point on the upper part of Robertson's Creek, a 

 small tributary of the Lerderderg. The total thickness in this ai-ea 

 is unknown, but similar flows occur at Flinders to a depth of 1-300 

 feet. In their present decomposed state these rocks are easily 

 •eroded. 



(e) Middle Tertiary. — This series includes a great vai'lety of 

 rock types all more or less easily ei'oded in places notably so. In 



l.".A 



