76 SUNKLANDS OF PORT PHILLIP BAY AND BASS STRAIT 
distance away from it. It is considered that these marine terraces 
were developed in the land-locked embayment behind the Bay Bar 
at the level of the eustatic rise of sea level when the delta and the 
lower portion of the valley were submerged. At that level, they 
were cut into the unresistant slopes rising from the submerged 
delta and the streams flowing into it, so that, apart from the slope 
given to them by the tilting, their elevation is everywhere the 
same, being fixed by a former sea level. On the sunkland, vertical 
erosion due to eustatic fall of sea level was restricted to the actual 
channel of the trunk stream and its tributaries, as in tectonic up- 
lift ; terraces so formed were typical fluviatile terraces, in contrast 
with the marine terraces formed some distance from the channels. 
Concerning interglacial rises above present sea level, Baly 
(1934) suggests that the higher sea levels of the interglacial 
stages are represented by marine terraces at heights averaging 71 
feet and 118 feet. He also gives Cooke’s correlation (1932) of 
marine terraces and Pleistocene stages along the south-eastern 
shore of the United States. The Wisconsin (and Iowan?) are the 
North American equivalents of the Wurm and these only are 
given here : 
Terrace 
Altitude 
(meters) 
Observed extension 
as described 
Corresponding stage of 
Glacial Epoch 
1st Wisconsin Glacial 
Talbot 
13 (51ft.) 
Delaware to Florida 
1st Wisconsin Interglacial 
• • • 
2nd Wisconsin Glacial 
Pamlico 
7-5 (29ift.) 
Maryland to Florida 
2nd Wisconsin Interglacial 
• • • 
• • • 
3rd Wisconsin Glacial 
Prince 
Anne 
4 (15^ ft.) 
3rd Wisconsin Interglacial 
4th Wisconsin Glacial 
Estimates of the interglacial rises from the marine terraces in 
Port Phillip Bay are, however, complicated by the down-tilting 
of the floor of the Bay. 
A first stage in the formation of marine terraces in Port Phillip 
Bay was that of the marine ridges at Altona which Hills (1940a) 
suggests may have been formed by the retirement of the waters of 
the Bay. The marine terraces surrounding the submerged delta 
have been modified to the extent that any ridges that may have 
been formed on their surfaces, have been planed out by wave 
action. Having been formed by the same eustatic adjustments 
that formed the fluviatile terraces in the Maribymong River, they 
probably belong to the Braybrook and Maribymong Cycles of 
erosion. 
