Geological History daring Tertiary Epoch. 
101 
CHAPTER X. 
Geological History during Tertiary Epoch . Erosion of 
Mesozoic llochs . Oligocene Deposits . Miocene — Fauna . 
Geographical Conditions . Miocene — Rivers, Lakes . 
Flora, Volcanic Action . Pliocene Deposits . Marine — 
Fluviatile . Newer Volcanic Lava-flows, Basin of Yarra , 
Post Tertiary Action and Deposits. Sand-dunes. Fauna. 
General Concluding Remarks. 
In drawing conclusions ns to the geological history of this 
country during the Tertiary epoch, the first fact to be observed is 
the enormous denudation during Upper Mesozoic and Lower 
Tertiary times, to which all pre-existing formations must have 
been subjected before even the lowest Tertiary deposits found in 
Victoria commenced to bo laid down. The Mesozoic rocks 
especially appear to have been entirely removed from large areas, 
and deep channels to have been eroded along their lines of junc- 
tion with other rocks. The sections obtainable in the Western 
Port and South Gippsland districts show this beyond a doubt, as 
we find that the great depression connecting Western Port with 
the Gippsland Lakes has been eroded along the northern line of 
junction of the Silurian and Mesozoic rocks, the former prevailing 
on the north, the latter on the south of the valley, though at one 
time the Mesozoic rocks must have oxtended right across, where 
the La Trobo and Lang Lang Valleys are now, aud flanked to a 
considerable height the southern slopes of the Silurian and granite 
ranges from Berwick to the Tyers River. On the southern 
boundary of the South Gippsland Mesozoic area a channel has 
similarly been eroded, where Corner Inlet and Shallow Inlet now 
lie, along the line of contact of the Mesozoic rocks with the 
Silurian and granite ; so that the section across from Wilson’s 
Promontory to the north of the La Trobo Valley shows deeply- 
excavated channels at either side, separating the ranges composed 
of Mesozoic rocks from the granite and Silurian mountains to the 
south and north. (Fig* 46.) 
In the same way the rocks of the Mesozoic ranges of the Cape 
Otway district liavo been, in a manner, isolated from the older 
mountain masses, which they once extended to and flanked. 
Such .remnants of Mesozoic rocks as that noar the Tyers River on 
