48 RIVER YARRA, VICTORIA 
9. Pleistocene eustatic low sea-levels caused streams to deeply 
erode the Older Basalt. The Newer Basalt at Melbourne lies 
in a valley below sea-level, and is itself affected by corrosion 
extending far below sea-level. It is therefore Pleistocene in 
age. During low sea-levels also, extensive calcareous dunes 
were built. High sea-levels have resulted in deposition within 
the low sea-level valleys, and in the planation of dunes. 
10. The Lower Yarra valley which was carved out by Pleistocene 
eustatie low sea-levels was flooded to form an estuary. The 
sea encroached still further to form Port Phillip Bay when 
(probably in late Holocene times) the development of Sel- 
wyn’s Fault caused block-tilting. 
11, The extrusion of the Newer Basalts caused ponding at Fair- 
field, and the forcing of the Lower Yarra against the southern 
wall of its valley as a marginal stream. 
12. This study is far from complete. It is but a step along the long 
road of research to a complete account of the physiography 
and palaeogeography of the River Yarra. 
ACKNOWLEDGEMENTS 
I am indebted to Messrs. I. J. O’Donnell, O.B.E., B.C.E., and 
W. Ozanne, M.C.E., of the Country Roads Board, for information 
relative to River Yarra bores, to Dr. D. E. Thomas of the Mines 
Department for information concerning Survey bores, and to 
Mr. M. Teese of M.M.B.W. for drafting Figure I. 
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