RIVER YARRA, VICTORIA 45 
The physiographic effect of the transgression was the opposite 
of rejuvenation (physiographic senescence, if a term may be 
coined), with the result that the products of erosion were rela- 
tively small. Widely distributed deposits of limestone, originating 
chiefly from the calcareous tests of marine organisms, were laid 
down. All in the area concerned in this study are Miocene in age. 
The Miocene deposits contrast strongly with the succeeding 
Pliocene Red Beds, which consist of sands and gravels resulting 
from the rejuvenation of streams following recession of the sea. 
At Beaumaris, on Port Phillip Bay south-east of Melbourne, 
remains of a Cheltenhamian (Upper Miocene) beach have been 
found above the Middle Miocene limestone. This suggests that 
regression of the sea was in progress in Upper Miocene times. 
The Rep BEDS 
Regression of the sea meant rejuvenation. Sands and torrent 
gravels were swept down the valleys and spread out on the former 
sea-floor left bare by the retreating sea. They thus formed a 
coastal plain covering the Nillumbik Peneplain and seaward 
slopes. 
The regression of the sea also meant the engrafting of the river 
system, so that a condition like that figured by Gregory (1903, fig. 
50) obtained. This was, of course, before the formation of Port 
Phillip. 
GLACIO-EUSTATIC CHANGES 
During the Pleistocene Period, the eustatic low sea-levels caused 
intense rejuvenation which resulted in the reduction of the Older 
Basalt lava field. The sections across the Yarra River described 
earlier in this paper show that the Older Basalt was practically 
stripped from the bed of the Kangaroo River at Melbourne. Hall 
(1909, p. 30) records that at Port Melbourne a bore pierced 170 
feet of deposits before reaching the bedrock. As already indicated, 
the low sea-levels resulted in corrosion to a depth of the order of 
500 feet on the site of the present Port Phillip Heads. 
Another process at work during low sea-levels was the building 
of ealeareous sand dunes now consolidated, and a notable feature 
of the coast (Hills 1939, Coulson 1940, Gill 1943, Keble 1946). 
These dunes partly filled the estuary cut by the rejuvenated river 
system, but the dunes themselves were planated when the sea 
advanced again. Later new dunes were built on the planated bases 
of the old ones. | 
The fact that the Newer Basalt was also stripped away from 
the bed of the Yarra at Melbourne during eustatic low sea-level or 
