Upper Tertiary . 
97 
On tho northern fall from the Main Divide, and passing under 
the Post Tertiary deposits of the plains, are gravels and conglom- 
erates, some of which are too widely spread to be due to other 
than littoral marine action ; among these are richly auriferous 
gravels and conglomerates. 
Fresh-water limestones of Pliocene age occur near Geelong, 
and in other localities. 
The Pliocene deposits due to fluviatile action appear to be 
younger than some of those of the same period which are of marine 
origin, and to be among the 
latest products of the epoch, 
though there is no doubt that 
the processes to which their for- 
mation is immediately due began 
very early in, if not previously to, 
tho Tertiary era. Those ancient 
river deposits consist of gravels, 
conglomerates, sands, and clays, 
occupying channels in the older 
rocks, and where they are 
worked for their associated gold 
are known as deep leads. As 
followed downwards towards 
tho sea or towards the Murray 
Valley, they merge into wide- 
spread marine deposits, the mar- 
gins of which mark the approxi- 
mate position of tho sea-board of 
the time when the lead channels 
were occupied by rivers. The 
gravels in these old river-beds 
are covered by thicknesses of 
from a few to several hundred 
feet of newer aqueous deposits, 
or layers of Newer Volcanic 
rock (basalt). 
Where there are two or more 
distinct layers of basalt, there 
are generally found interbodded 
between them deposits of clay, 
sand, gravel, and occasionally 
lignite of varying thickness. 
(Fig. 44.) 
The deep leads of Ballarat, 
Haddon, and Daylesford are 
types of the lava-covered Upper Tertiary fluviatile deposits, while 
the leads of Chiltern, Iluntly, and Dunolly are instances of those 
covered only by newer sedimentary accumulations. 
