TECTONIC CHANGES IN MONTAGUE HARBOUR AREA
Although isostatic and eustatic changes(regional and global sea-level changes)
were probably the major cause of the eventual breaching of the northwest
end of the harbour, there is evidence that regional tectonism also
played a role.
There were two tectonic events recorded by Mathewes and Clague(1994) that
apparently caused subsidence on Vancouver island. At least one of these
events is also recorded in the section at Montague Harbour.
The first tectonic event occurred approximately 3600 years BP and is marked
by the stratigraphic transition from nearshore intertidal deposits to a
subtidal environment characterized by abundant organic matter and foraminiferal
The evidence for the second tectonic event can also be seen in the stratigraphic
record and is marked by a transition from subaerial exposure to a nearshore
possibly subtidal environment which suggests a second subsidence event.