Wisconsin Glaciation and the Labrador Sector of the Laurentide Ice Sheet

Labrador Sector, Laurentide Ice Sheet

Little is known about the initial development of the Labrador sector of the Laurentide Ice Sheet or the course of glacier movements that led to the ice cover of the entire region between the Labrador coast and western Manitoba, and possibly beyond. It is probable that in response to a change in climate, the Lake Plateau of central Quebec-Labrador developed an ice cap by "instantaneous glaciation", followed by radial outflow. The early influence of an open Hudson Bay in the development and differential expansion of the ice cap towards the west was favoured by (Hare, 1951) but not on climatological grounds, by. The prevaling southwesterly winds from the mid-continent no doubt contributed to southwestward expansion of the ice sheet towards Ontario and the Great Lakes region. There were probably local centres of excessive snow accumulation in the marginal zone of the expanding ice sheet; these may account for glacial lobations and resulting striae which in many areas diverge markedly from the general, deglacial, trend. Early in Classical Wisconsin time the glaciers flowed off the Laurentian Highlands into the St. Lawrence Valley and, upon filling the valley, sought escape northeastward towards the Gulf of St. Lawrence and southwestward towards the Ontario Basin. Strong eastward ice flow was long-continued down the Saguenay River and then northeast down the St. Lawrence River as indicated by iceflow features on the land and a very deep channel in the St. Lawrence River beginning at the mouth of the Saguenay River. The channel extends east-southeastward across the Gulf of St. Lawrence through the Cabot Strait and then to the edge of the continental shelf, and is known as the the Laurentian Channel. Ice-flow features give some indication that the ice-flow divide in the St. Lawrence Valley may have migrated westward from well east of the Saguenay River to somewhat west of the Saguenay during Wisconsin time. The Laurentide ice upon filling the St. Lawrence Valley and flowing along it sought escape southward through cols in the eastern part of the Notre Dame Mountains and hence combined with elements of the Applachian Glacier Complex. Information on the retreat of the Labrador sector of the Laurentide Ice Sheet is naturally more abundant than on the advance or build-up stages. The present surface bears a record of the last glacial events, modified only in part by postglacial changes, whether erosional or depositional. After the Wisconsin glacial maximum it is probable that there was thinning of the ice sheet over a broad marginal zone as the ice front retreated. The following discussion attemps to follow the major changes and events as the ice front receded from various parts of the country.

  • Back To the Beginning