28 RIVER YARRA, VICTORIA 
definition, suggested that country east of the Queenstown-Christ- 
mas Hills-Mooroolbark line be included (p. 474). Hills (1984, p. 
163) has shown that Gregory was in error concerning the position 
of the ancient Divide. He also took Gregory’s second definition, 
describing the Yarra Plateau as ‘‘the country from the Christmas 
Hills to the Plenty River, and from the Kinglake Escarpment to 
the divide on the Mitcham Axis.” 
In this paper Hills’ definition is accepted, with a modification 
of the southern boundary of the Plateau. The map (Fig. 3) and 
sections (Fig. 4 a-c) show that the tops of the hills forming the 
old Yarra Plateau (as defined by Hills) as far south as Kangaroo 
Ground and Research are all about 600 feet to 650 feet above 
present sea-level. This is significant, because it is the level of 
the pre-Older Basalt terrain, as shown by the existing residuals. 
Diamond Creek as far as Hurstbridge plus Arthur’s Creek on 
the west, and Watson’s Creek on the east, are apparently streams 
that developed marginally to the Older Basalt flow. The up- 
stream end of Diamond Creek, found north-east of Hurstbridge, 
is apparently a cross-cutting lateral. The ridges between these 
streams are apparently remnants of the old terrain which have 
been but recently stripped of their Older Basalt cover. 
The relative positions of the 600 ft. summits suggests that those 
N.N.W. of the Kangaroo Ground basalt, and those forming a 
ridge between Arthur’s Creek and the upper part of Diamond 
Creek, are the course of the pre-Older Basalt river. The ridge 
followed by the road from Panton Hill to Queenstown (which 
reaches 700 ft. in places) would then be the eastern side of the 
valley, and the ridge from Yarrambat to Doreen (which reaches 
725 ft. at Doreen) would be the western side of the valley. 
Doncaster 
Red Bed Outlier 
OB Residual 
4 Lilydale Rey 
Cove Hill 
LEVEL OF NILLUMBIA PENEPLAIN 400° TO 459. 
SECTION FROM DONCASTER TO LILYDALE. 
FIG. 4a 
Section drawn from contours of Military Map, Ringwood Sheet, to show how 
the Nillumbik Peneplain stretched across as far as the Dandenong Ranges, 
and how the Older Basalt of the Wurrunjerri River flowed over it. 
The general accordance of summit levels in this area gives indi- 
cation of a definite terrain. As the Older Basalt and/or associated 
sands and gravels rest on these levels in a number of places, we 
know that this terrain is the pre-Older Basalt one, and so previous 
