:30G Charles Feaner 



XI.— Chronological Record of the Physiography of 

 the Area. 



This section is intended to act partly as a summary of the 

 physiographic and geological events referred to in the preceding 

 pages. Fig. 39 is drawn to recapitulate the physiographic history 

 of this area in an " erosion column,'^ analagous to the sedimenta- 

 tion column of geologists. Diastrophic periods of folding and 

 faulting are suggested, and periods of vulcanicity and sedimen- 

 tation are marked as breaks in the progress of erosion. Leaving 

 out the Port Phillip sunkland, the underlying rocks of which are 

 not exposed in this area, there is no evidence of any extensive 

 marine transgression since the close of the lower Ordovician period. 

 Traces of the ''buried landscapes" of various periods are here 

 and there available, and these liave been marked in the column. 

 Each geological system was given* an approximately equal length of 

 the column, which is therefore not to be regarded as a true '' time 

 line." 



It will be seen from the column that, following the great lower 

 •Ordovician deposition, there has been no further marine sedimen- 

 tation of any note in this area. 



In consideration of the possibilities of various periods of sedi- 

 mentation having affected marginal portions of the Werribee area, 

 certain of these periods are indicated by small triangular insets on 

 the left-hand side of the cohinm (Fig. 39). Such periods may sug- 

 gest, however vaguely, something of the general nature of the topo- 

 graphy of this area during the long periods of erosion that followed 

 the Avithdrawal of the sea at the close of the lower Ordovician 

 period. 



As already pointed out (Section VII (a) ), the lower Ordovician 

 sea or gulf covered the whole o^f the area here discussed, and 

 extended well beyond its boundaries. Subsequent to the recession 

 of this sea, a further marine transgression occurred in upper Ordo- 

 vician times. Since richly fossiliferous rocks of this age occur on 

 the Mornington Peninsula (east of Selwyn's fault), and probably 

 below the Silurian at Diamond Creek (ref. 36), it is possible that 

 the shores of this sea lay partly within the Werribee area. Simi- 

 larly also the later marine encroachment of Silurian times is 

 recorded in the rocks closely contiguous) to tliis area, at and imme- 

 diately westward of Melbourne. 



There is evidence in the folding of the lower palaeozoic rocks tliat 

 in middle to upper palaeozoic times great ranges of fold moun- 



