SUNKLANDS OF PORT PHILLIP BAY AND BASS STRAIT 103 
Tideways through the Nepean Bay Bar connected that part of King Bay 
behind it with the open sea in front of it. 
Continued rise of sea level submerged the tideways, fluvio-estuarine sediments 
were deposited along or near them, and in some places shallow water 
limestones accumulated. 
These deposits are found on the platforms, and represent periods of standstill 
in tectonic movement. 
During eustatic fall of sea level in the glacial stages or tectonic uplift — 
With the retreat of the sea the dune cycle commenced. In the early stages 
the tideways again funetioned (the present stage of the shoal water in 
the southern part of Port Phillip) until the level of the open part of 
King Bay in front of the Bay Bar was lower than the beds of the 
tideways themselves. With continued retreat, the uncovered Bay Bar 
was piled up into dunes (cf. K. W. Sayles, 1931, and E. S. Hills, 1936). 
Bore No. 4 Wannaeue, which is the most reliable for observa- 
tion, shows that on the 35-fathom (210 feet) platform (Fig. 4) 
approximately 57 feet (153 feet to 210 feet) of sediments 
accumulated, some of which were shallow marine, others 
apparently terrigenous, but all of fluviatile origin, and composed 
for the most part of material derived from outside the area of the 
Bay Bar : they were obviously deposited during a eustatic rise of 
sea level. They rest on a dune series, and are succeeded by the 
Upper Dune Series, evidence of the fact that both before and 
after their being deposited, the sea had retreated from the area. 
Likewise, in the Sorrento Bore (Fig. 4), the period of eustatic 
rise corresponding to 210 feet in the Wannaeue Bore is considered 
to be the shallow-water limestone of small, but unascertained 
thickness, with marine bivalve and gasteropod shells at 197 feet. 
This also occurs above dune-rock, is succeeded by the Upper Dune 
Series, implying, as in the Wannaeue Bore, retreat of the sea. 
The period occupied by the accumulation of the shallow marine 
and terrigenous sediments in both bores probably represents a 
period of standstill in the general tectonic subsidence. 
The 45-fathom platform (Fig. 4) is shown in the Wannaeue 
Bore to be covered by heavy drift from 256 feet to 262 feet at 
which depth the bore ended. Overlying this is a dune series 46 
feet thick. In the Sorrento Bore (Fig. 4), the equivalent sample 
is the shallow water limestone, with numerous casts of bivalves 
at 259 feet (L.W.M.). Under it at 265 feet (L.W.M.) is a liver- 
coloured clay with fine ferruginous sand and a few quartz 
particles; this is unfossiliferous. Below it is dune-rock at 288 
feet (L.W.M.) and at 314 feet (L.W.M.) , a calcareous quartzose 
sand and grit. These deposits also indicate marine transgression 
and retreat, implying eustatic rise and fall of sea level. 
