252 W. N. THAYER 
THE ST. LAWRENCE VALLEY PROVINCE 
The St. Lawrence Valley, bordered on one side by the New 
England region and on the other by the Laurentian Plateau, is a 
strip of territory sufficiently different in structure, topography, and 
physiographic history to require separate discussion. This is 
known to Canadian geologists as the St. Lawrence Lowlands. This 
name is perhaps better suited to designate the province than St. 
Lawrence Valley as the province has a greater extent than the mere 
valley of the river. 
Commencing near the city of Quebec, these lowlands stretch on both sides 
of the St. Lawrence River, southwestward, with slightly diverging boundaries 
until at Montreal the level country is approximately 120 miles wide. Beyond 
Montreal the northern boundary pursues a westward course up the Ottawa 
Valley to a point about 50 miles beyond Ottawa city, where a ridge of broken 
country, a low spur of the Laurentian Highlands, projects southward, crossing 
the St. Lawrence between Brockville and Kingston to join the elevated Adiron- 
dack region of northern New York. 
Young extends the province beyond this spur and includes the 
territory of the Ontario Peninsula “lying between Lakes Huron, 
Erie, and Ontario, and bounded on the north by a nearly east-west 
line from Kingston to the foot of Georgian Bay.” In this paper 
this territory has been included in the Lake section, and the Lauren- 
tian spur should probably be regarded as the natural boundary of 
the lowlands. This opinion is supported by Kindle and Burling, 
who write that “the Paleozoic plain of the Ottawa and St. Lawrence 
valleys lies between the Laurentian Plateau on the North and the 
Adirondack uplift on the South, and extends eastward from the 
Archean shield at the head of the St. Lawrence to the zone of 
Appalachian folding east and southeast of Montreal.’ 
Branching off to the south from this province near Montreal 
is the Champlain-Hudson Valley, which is topographically similar 
to the St. Lawrence Valley and which may be regarded as a section 
of the province. 
The main division of the province, that which embraces the 
valley of the St. Lawrence River, is a plain floored with Paleozoic 
1C. A. Young, op. cit., p. 60. 
2. M. Kindle and L. D. Burling, op. cit., p. 9. 
