RIVER YARRA, VICTORIA 37 
, (6) Anakies-You Yangs Divide. This divide separated the 
river which flowed from the direction of Bacchus Marsh and the 
Maude River (see Fig. 6). The Anakies and You Yangs both 
consist of granitic rocks. They must have constituted a prominent 
range in early Tertiary times. They are still very prominent 
monadnocks, The ?Oligocene lignite in the Bacchus Marsh-Altona 
dines (Fig. 5) indicates the alignment of the drainage at that 
ime. 
Further south-west the palaeogeography has not been studied 
sufficiently to indicate the pre-Older Basalt divide or divides. 
Since then the Otway Ranges have been uplifted, as is indicated 
by their very young physiography. This has naturally greatly 
complicated the reconstruction of the early Tertiary terrain. 
However, the basalt at Airey’s Inlet indicates the valley of 
some stream there. Probably the presence of tuff indicates that 
there was a vent at no very great distance. 
EARLY TERTIARY RIVERS 
(1) Wurunjerri River. This flowed from the Woori Yallock 
Basin round the northern end of the Dandenong Ranges igneous 
complex, southwards through where Lilydale now stands and, 
* following the Arthur Range, through Frankston and Mornington, 
and so to the main north-south stream—the Melbourne River. 
Older Basalt residuals and associated fluviatile deposits are 
found in the Woori Yallock basin (Edwards, 1940) and in the 
Gruyere and Lilydale districts (Gill, 1942), Older Basalt is also 
preserved in the lower part of the course of this ancient stream 
by location below sea-level and by protection from overlying rocks. 
The basalt has been found in bores near Mordialloe and near 
Frankston in the Carrum Swamp area. It also occurs in Baleombe 
Bay where it is covered by the type Baleombian strata. 
(2) Kangaroo River. The Yarra Plateau, as defined in this 
paper, was traversed by a river whose deposits are to be seen under 
the Older Basalt at Kangaroo Ground and in adjacent areas. 
When a river valley is filled with basalt, its thalweg naturally has 
the thickest covering of lava over it. For this reason the thalweg 
is usually the last part to be eroded. Marginal streams are set up 
which gradually work in to the centre, and cross laterals divide 
the flow into residuals. Applying this idea, we may infer that 
the curved string of hill-tops at Yarra Plateau level north of 
Kangaroo Ground indicates the course of the pre-Older Basalt 
river (Fig. 3). These are uncovered residuals (Keble, 1918) and, 
being the last to be uncovered, we may assume that they once 
