60 
RIVER TERRACES OF THE MARIBYRNONG RIVER, VICTORIA 
The Keilor and the Braybrook Terraces occur at short 
intervals between Dry Creek and Ascot Vale Grap, and the 
Maribyrnong Terrace as far downstream as the Footscray Warp. 
The Maribyrnong Eiver has been entrenched upstream from the 
Yarra Delta; it formerly flowed east of Quarry Hill, but the 
entrenclmaent was responsible for the breaching of the rock 
barrier west of Quarry Hill, to form the Ascot Vale Gap. The 
material removed has been progressively deposited in the 
entrenchment, and has formed the Estuarine Flood Plain and 
the Yarra Delta. The Estuarine Flood Plain is a northerly 
prolongation of the Yarra Delta, and is mapped by Aplin (1858) 
at the direction of A. E. C. Selwyn (then Director of Geological 
Survey) on Quarter Sheet 1 N.W. as “Post Pliocene-raised 
beaches, estuary beds, etc.” The surface bed consists of 3 feet 
of grey soil resting on 5 feet of yellow clay. Both beds are 
unfossiliferous, but crossing the Estuarine Flood Plain, a short 
distance below the Ascot Vale Gap, is a drain in the bottom of 
which, and also in the excavated material beside it, are a number 
of Eecent estuarine shells that may have come from a bed hidden 
beneath the silt in the drain. It is scarcely necessary to add that 
such a careful observer as Selwyn would not record the estuarine 
nature of the Flood Plain without definite evidence of such. 
The Keilor, Braybrook, and Maribyrnong Terraces have not 
been preserved between the Footscray Warp and Port Phillip 
Bay, but on the floor of the Bay there is evidence of cycles of 
erosion in the form of marine platforms and delta deposits that 
may possibly be correlated with the Maribyrnong Eiver cycles. 
The heights of the terraces above L.W.M. decrease as they are 
followed downstream from Dry Creek, but their heights above 
