Mem. Nat. Mus. Vict., 14, Pt. 2, 1946. 
THE 
SUNKLANDS OF PORT PHILLIP BAY 
AND BASS STRAIT 
By R. A. Keble, F.G.S., 
Palaeontologist, National Museum of Victoria. 
Figs. 1-16. 
(Received for publication 18th May, 1945) 
The floors of Port Phillip Bay and Bass Strait were formerly 
portions of a continuous land surface joining Victoria with 
Tasmania. This land surface was drained by a river system of 
which the River Yarra was part, and was intersected by two 
orogenic ridges, the Bassian and King Island ridges, near its 
eastern and western margins respectively. With progressive 
subsidence and eustatic adjustment, these ridges became land 
bridges and the main route for the migration of the flora and 
fauna. At present, their foimer trend is indicated by the chains 
of islands in Bass Strait and the shallower portions of the Strait. 
The history of the development of the River Yarra is largely that 
of the former land surface and the King Island land bridge, and 
is the main theme for this discussion. 
The Yarra River was developed, for the most part, during the 
Pleistocene or Ice Age. In Tasmania, there is direct evidence of 
the Ice Age in the form of U-shaped valleys, raised beaches, 
strandlines, and river terraces, but in Victoria the effects of 
glaciation are less apparent. A correlation of the Victorian with 
the Tasmanian deposits and land forms, and, incidentally, with 
the European and American, can only be obtained by ascertaining 
the conditions of sedimentation and accumulation of such deposits 
in Victoria, as can be seen at the surface, or as have been 
revealed by bores, particularly those on the Nepean Peninsula; by 
observing the succession of river terraces along the Maribyrnong 
River ; and by reconstructing the floor of Port Phillip Bay, King 
Bay, and Bass Strait, and interpreting the submerged land forms 
revealed by the bathymetrical contours. 
This contribution deals with the former courses of the Yarra 
River as a tributary stream to the trunk stream, the Tamar Major 
River, when the Yarra flowed over the land surfaces that are now 
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