THE PHYSICAL EVOLUTION OF ACADIA. 
11 
the older rocks beneath the Cambrian are softened and decom- 
posed at the contact as with the basement beds of the latter, 
as though they had for a long time been exposed to atmos- 
pheric wear before being buried under volcanic ashes, etc 
Another reason is that while one Cambrian basin may rest 
on Huronian, another has its foundation on the Laurentian 
rocks; this implies the erosion, in some places, of the whole 
Huronian terrane, a mass of enormous thickness, before the 
deposition of the Cambrian. 
As contrasted with the enormous bulk of the Huronian forma- 
tion, those of the Cambrian time in this region are of modest 
proportions, unless one gives a large value to the volcanic masses 
which, in some districts, lie at the base of the Cambrian. These 
seem always related to a subsequent subsidence which brought 
in the sea upon the land; thus, the Cambrian basins (marine 
deposits) were, as it were, a consequence of these eruptions 
The Loch Lomond and the Quaco hills in southern New 
Brunswick are the best known bodies of effusives of this time 
and between them lies one of the deepest basins of Cambrian 
sedimentary rocks of which the Acadian region can boast, and 
it is in this that the most complete series of Cambrian faunas of 
this part of the world has been discovered. 
In like manner in Cape Breton the Cambrian basins are 
underlain by great masses of effusive rocks; this is particularly 
marked on the Mira River, but is also seen elsewhere. The 
undermining of the earth’s crust by such agencies was a pre- 
disposing cause for the production and also the preservation 
of such deep Cambrian basins. Yet we know from the similarity 
of the succession of strata in New Brunswick and in Cape Breton, 
that the agencies for its production were common to the whole 
region of Acadia; and that these now isolated patches of sediment 
are but small remnants of what was once a widely extended 
terrane. 
Such being the case the description of the variation in the 
sedimentation of one basin will, with considerable accuracy, 
apply to all. 
Passing the volcanic formation and its related red and greenish 
sandstones and shales (Etcheminian), the members of division 
