72 SUNKLANDS OF PORT PHILLIP BAY AND BASS STRAIT 
Gellibrand its headwaters are known as Hobson’s Bay. The 
pear-shaped symmetry of Port Phillip is varied by the Bellarine 
Peninsula to the south-west : along the north shore of this 
Peninsula, an arm, forming the Geelong Inner and Outer Har- 
bours, extends in a W.S.W. direction. There are several minor 
indentations in the shores of Port Phillip Bay such as Half Moon 
Bay, Davy Bay, Balcombe Bay, Dromana Bay, Swan Bay, and 
Altona Bay : a deep in the south-east portion is known as Capel 
Sound. 
Long stretches of the eastern shores are low and shelving — they 
consist mainly of littoral, alluvial, or delta deposits, which have, 
at places, been piled up as dunes, or scoured out as submarine 
ridges uncovered, it is thought, by the eustatic fall of sea level. A 
considerable portion of these littoral and delta deposits has been 
submerged by the tectonic subsidence of the Port Phillip Sunk- 
land. The bathymetrical contours of the submerged delta 
deposit at the head of Port Phillip show three outlets of the Yarra 
Biver — its present one near Williamstown, and two older ones at 
Port Melbourne and St. Kilda. Delta deposits also occur at the 
mouth of the Elsternwick Creek, between Mordialloc and Frank- 
ston, where they are fringed with dunes, at the mouth of 
Balcombe Creek, and between Mount Martha and Arthur’s Seat. 
On the northern shore of Corio Bay, east of Limeburner’s 
(Galena) Point, there are also delta deposits. On the eastern 
shore at Carrum, the shore of the delta deposits has advanced 
seawards which, according to Hills (1940) is due to uplift, not 
progradation. The coast is clifEed between these low stretches of 
coast. 
The foiiner shore line of the Inner Basin (Fig. 2) between the 
north end of Port PhiUip Bay and Mordialloc is a down-warped 
coast; the undulating sedimentary beds exposed along that part 
of the shore were tilted seawards until they disappeared under 
the waters of the Bay. From this earlier shoreline, the present 
one has receded through erosion by the 2 knot current that sets 
from Hobson’s Bay, until it has reached its present position. 
From Frankston to Arthur’s Seat, the coast is due to the mono- 
clinal flexure known as Selwyn’s Fault. Here, too, the original 
shore-line formed by the tilting on the flexure has receded by 
foreshore erosion. The north shore of the Bellarine Peninsula 
consists of ferruginous sandstone. Tertiary basalt, limestone, and 
Pleistocene basalt; it is a fault coast (Coulson 1939) that has 
receded before the erosion of the tidal stream. 
The western shore of the Inner Basin affords a contrast to the 
eastern shore. For long stretches, it is flat and prograded; it is 
