SECTION IV., 1886. [ 189 ] Trans. Roy. Soc. CANADA. 
X.—On the Glaciation and Pleistocene Subsidence of Northern New Brunswick and 
South-Eastern Quebec.’ By R. CHALMERS. 
(Communicated by Dr. George M. Dawson, May 27, 1886.) 
The surface geology of Eastern Canada presents a number of interesting problems 
for investigation, some of which have given rise to considerable discussion. The two 
most important of these, perhaps, are the glaciation, whether by land ice or icebergs, or 
both, and the oscillations of level the region underwent during the Post-Tertiary period. 
This paper is intended as a brief contribution towards the elucidation of these questions. 
Among a large number of geologists in America the glacier theory, with, perhaps, 
some modifications, is accepted. This theory explains the glacial phenomena of Eastern 
Canada and the New England States by supposing a thick sheet of ice of early Post- 
Tertiary age to have accumulated on the surface of the country, which, slowly moving 
southward from the Laurentide Mountains, crossed the St. Lawrence valley, over-riding 
the Notre Dame Range, passing thence down the Atlantic slope towards the ocean, striat- 
ing the rocks and transporting masses of debris in its course, such as boulder-clay, erratic 
blocks, etc. Its general adoption is, perhaps, due principally to the fact that most of the 
striæ on both sides of the mountain range referred to, as well as on the south-east slope of 
the Laurentides, have approximately the same course, that is, they trend nearly south-east 
and north-west, or about at right angles to the axis of the Notre Dame Range. But the 
theory has other features to recommend it, being comprehensive and grand, and apparently 
at once solving all the problems pertaining to the glaciation of the region. Observations 
made by Sir W. Dawson in the St. Lawrence valley for many years, however (see his “ Notes 
on the Post-Pliocene Geology of Canada,” contributed to the “ Canadian Naturalist,” in 1872, 
and also “ Acadian Geology,” 3rd edition, 1878), led him to adopt a different conclusion, and 
he has long contended against the above view. In the course of his investigations, he 
ascertained that drift-ice (icebergs, coast ice, etc.) had been transported up, and probably 
down, the St. Lawrence valley during the ice age, the chief abrasion and denudation having 
been apparently caused by a south-westward flow of these. He also found evidences of 
local glaciers having debouched into this valley from the north, following the courses of the 
Saguenay and Murray Bay Rivers, etc.; and that the Pleistocene subsidence of the region 
had been as much as 470 feet below the present sea level in some places, especially in the 
vicinity of Montreal. Boulders of Laurentian rocks, it was also observed, had been drifted 
up and down the valley. These facts seemed conclusive against the theory of a glacier 
having moved across the St. Lawrence valley south-eastwardly from the Laurentides, pur- 

1The term “Pleistocene ” is here employed in the sense in which it is used in Dr. Archibald Geikie’s Text 
Book of Geology, 2nd edition; and as equivalent to the term “ Post-Pliocene” of Sir W. Dawson’s Acadian 
Geology, 3rd edition, to distinguish the subsidence under consideration from that which took place in the Recent 
or Prehistoric period. 
