RIVER TERRACES OF THE MARIBYRNONG RIVER, VICTORIA 59 
shore of Port Phillip Bay. One zone crosses the Maribyrnong 
River between Albion-Broadmeadows railway bridge and the old 
Keilor school (Fig. 4) ; another — the Footscray Warp — is evident 
in the section (Fig. 4) on the west side of the River at Footscray, 
about a quarter of a mile north of the Ballarat Road. The tilting 
on the Footscray Warp brought about the complete submergence 
of the Port Phillip Sunklands — Port Phillip Bay then assumed 
its present form. No fracture lines are known in any part of the 
Maribyrnong River valley or the Keilor Plains lava field. 
Fluviatile Deposits of the Maribyrnong Valley 
The earliest reference to terraces in the Maribyrnong River 
valley appears to be that of Officer (1893) at Keilor, while 
Hills (1939) noted paired terraces at West Essendon and at 
Maribyrnong (Ascot Vale Gap). 
All the fiood plains subsequent to the Keilor Flood Plain were 
formed of the resorted material of that fiood plain, and are 
lithologically similar. The only way of distinguishing between 
them is by noting their relative positions in the field, and by 
accurate levelling. There are no traces in them of volcanic 
ejectamenta from adjacent scoria cones such as the tuffs of 
the Camperdown area (Grayson and Mahony, 1910), and this 
indicates that none of these scoria cones were in eruption while 
the flood plains were being formed. 
The six major episodes evident in the development of the 
Maribyrnong River from Dry Creek to Ascot Vale Gap are: 
First, a cycle of erosion — the Keilor Cycle — which started on the Keilor 
Plains lava field. During this cycle, the valley was vertically eroded, 
the erosion reaching the beds underlying the basalt; this was followed 
by lateral erosion, when the Keilor Flood Plain was deposited to a 
depth of 45 feet. 
Second, a cycle of erosion — the Braybrook Cycle — during which the Keilor 
Flood Plain was entrenched, the Keilor Terrace formed, and the 
Braybrook Flood Plain deposited. 
Third, a cycle of erosion — the Maribyrnong Cycle — during which the Bray- 
brook Flood Plain was entrenched, the Braybrook Terrace formed and 
the Maribyrnong Flood Plain deposited. 
Fourth, the beginning of a cycle of vertical erosion, due partly to eustatie 
adjustment and partly to the Footscray Warp, during which the 
Maribyrnong Flood Plain was entrenched, and the Maribyrnong 
Terrace formed. 
Fifth, Post-glacial 15 to 20 feet eustatie rise of sea level shown by wave 
platforms, and ridges that were .submarine banks on the Yarra Delta 
and the shores of Port Phillip Bay. 
Sixth, eustatie fall of sea level, and resumption of the vertical erosion started 
in the fourth episode. 
