102 
Geology and Physical Geography : 
Fig. 46. 
the north of the La Trobe Valley show, beyond question, that 
the Mesozoic rocks once flanked the slopes of the main mountain 
system. 
It is principally in hollows and channels 
eroded since the formation of the Mesozoic rocks 
that the marine Tertiary deposits have accumu- 
lated, though the outlines of such channels may 
have been formed at far earlier dates, and we 
are therefore forced to the conclusion that the 
natural operations which were in progress on 
what is now the Victorian land surface were 
confined, during the latest portion of the 
Mesozoic and the earliest part of the Tertiary 
periods, to denudation and removal rather than 
accumulation of rock materials. 
The Mesozoic rocks themselves testify that at 
the completion of their deposit the land was sub- 
merged to a depth at least 2,000 feet lower than 
at present, even allowing for the fresh-water 
origin of many of the beds. It can only be 
inferred, therefore, that towards the close of the 
Mesozoic period an upward movement took 
place, and that during long ages the action of 
fluviatile and littoral denudation on a rising land 
surface sculptured and eroded the previously- 
formed rocks, and made inlets and straits near 
the coast line, insulating such tracts as the Cape 
Otway and South Gippsland Ranges, and eroding 
river channels in the elevated country. 
With renewed depression commenced the 
deposit of the Lower Tertiary formations, and 
at that time the aspect and orographical con- 
figuration of the country must have been very 
different from what it is now. Western Port 
and the Gippsland Lakes were connected by a 
strait, and another strait connected Port Phillip 
with Warrnainbool and Portland, thus insulating 
from the main laud the South Gippsland Ranges 
in the east, and the Cape Otway Ranges in 
the west. The sea washed the slopes of the 
main mountain system from the Snowy River 
round to the bases of the Grampians, extending 
in inlets up to Bacchus Marsh, Meredith, and 
the Leigh River Valley, and overspreading the greater part of 
■the Western District and the low country bordering the Murray. 
During the progress of deposit of the Oligocene clays, and the 
Miocene calcareous beds, shell-fish in great variety of species 
