70 
Geology and Physical Geography : 
The land was in process of submergence, and materials washed 
from the sides of the fiord, by terrestrial and littoral denuding 
action, were deposited and arranged in its bed ; this arrangement 
was probably aided by tidal action, which would exert a powerful 
influence in such narrow confines. 
During such deposit volcanic activity, which had been quiescent 
during the latter part of the Middle Devonian period, again broke 
forth and produced the contemporaneous igneous sheets. With 
the sinking of the land this filling up process, by aqueous deposit 
and lava-flows, was continued to the extent of several thousand 
feet, and by the time it was accomplished the mountains of the 
land surface on either side had been greatly reduced in height by 
denudation, though they still rose above the ocean. The denuda- 
tion to which both Lower and Upper Palaeozoic rocks have been 
subjected since the formation of the latter is incalculable, and has 
exerted the most remarkable effect in obliterating from extensive 
tracts every vestige of the Uppor Palaeozoic rocks which once 
overspread them. 
The Mount Tambo outlier is apparently a portion of the de- 
posits distributed in another fiord similar to that last described, 
and separated from it by a mountainous land surface. 
It is not to be supposed that the height of over 4,000 feet, to 
which we now find the Upper Palaeozoic rocks in Victoria, represents 
the level to which they accumulated for any considerable distance 
away from the shore-line of their period. The thickest deposits 
were evidently accumulated at no very great distance from the 
land surface, whence their component materials were derived, and 
the beds sloped away or thinned out seaward in every direction 
from the flanks of the older rock foundation on which they were 
deposited. 
The beds generally have been comparatively very little affected 
by upheaval or lateral compression, and in many cases their slope 
appears to be that at which they were originally laid down. A 
certain amount of uplifting and compression has certainly taken 
place, but to an insignificant extent compared with what the older 
rocks have been subjected to. 
