66 RIVER TERRACES OF THE MARIBYRNONG RIVER, VICTORIA 
and terraces formed in the delta deposits on the slopes of the 
entrenched portion. They appear to have been wave platforms 
formed during eustatic lowering of sea level. 
Correlation of the Maribyrnong River Terraces 
It is submitted that the Keilor Plains lava field on which the 
Keilor, Braybrook, and Maribyrnong Flood Plains were formed 
is of Pleistocene age, presumably Middle Pleistocene. The 
Keilor, Braybrook, and Maribyrnong Cycles occured in connected 
sequence during the time inteiwal between the formation of the 
Keilor Plains lava field and postglacial 15-20 feet eustatic fall of 
sea level. By tieing them up with the 15-20 feet fall of sea 
level, and placing the physiographical events that preceded it in 
logical sequence, the three cycles seemingly fall into the Upper 
Pleistocene, and correspond to the period when the Upper 
Pleistocene glacial and interglacial stages occurred in Europe. 
In attributing the deposition of the flood plains and their sub- 
sequent terracing to eustatic adjustment, we desire to emphasize 
the fact that there is no evidence of Pleistocene or Recent 
glaciation in Victoria. The absence of systematic investigations 
as to the migration and extinction of the marsupials and the 
difficulty of defining cultures and industries in connection with 
the Australian aborigines, make it impossible to apply European 
methods in subdivi^ng the Australian Pleistocene. We have 
relied on the world-wide eustatic adjustments associated with the 
glacial and interglacial periods of the Northern Hemisphere, and 
correlated our terraces with them. The contemporaneity of the 
Tasmanian and European stages is probable, but has not been 
definitely established. It is submitted that, if the Maribyrnong 
valley terraces are not strictly correlative with the European 
stages, the fact that we have tied them up with the Recent 15-20 
feet fall of sea level, and shown that they preceded it in orderly 
sequence, proves that their age cannot greatly differ from that of 
those stages. 
In regard to regional tectonic movements, it has been pointed 
out that the Keilor Plains lava field has been tilted seawards, but 
the tilting has retarded rather than assisted entrenchment. Its 
effect has been to make the eustatic falls appear less than they 
actually were. The greatest amount of entrenchment appears to 
be less than 40 feet. The streams of each of the cycles debouched 
into an almost completely enclosed bay situated on what is now 
the Port Phillip Sunkland or Port Phillip Bay. On the floor of 
the latter there is evidence of deltas and other estuarine land 
