44 RIVER YARRA, VICTORIA 
latter locality between the southerly extension of the Western 
Quartzites and a granitic intrusion (part of the old Arthur 
Range). The basin is one of differential erosion, and it is to be 
noted that a branch of the Dandenong Creek south-east of Ring- 
wood has succeeded in breaching the Western Quartzites at a 
weak place and in corroding a young valley west of the main 
quartzitie horizon. 
The headwaters of the Dandenong Creek are very little different 
in level from Brushy Creek, which flows into the Yarra. In a 
short time, from a geological point of view, the Dandenong Creek 
will eapture Brushy Creek and reverse its direction of flow, so 
that the Yarra will flow down the Dandenong Creek. Thus the 
early Tertiary drainage system of the Wurunjerri River will be 
re-established. However, the constriction at Dandenong will no. 
doubt cause flooding, and the river will cut a gorge there. 
FIG. 8 
Map to indicate extent of Miocene marine transgression. Nearly all deposits 
are found below the level of the Nillumbik Peneplain. 
TERTIARY MARINE TRANSGRESSION 
After the Older Basalt had been eroded (a time interval of 
unknown duration), a marine transgression of the land on a large 
scale took place. Figure 8 shows the approximate extent of this 
transgression in Victoria. The whole of the seaward half of the 
Port Phillip river system was drowned, the Yarra was betrunked, 
eur former branches (like the Barwon) became independent 
streams. 
