Relict ice-scour marks and late phases of Lake Agassiz in northernmost Manitoba

• Published in: Canadian Journal of Earth Sciences
• Main Author: Dredge, L. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1982
• Subjects: General Earth and Planetary Sciences; Hudson Bay; Hudson; Glacial Lake; Tyrrell; Sprott Lake
• Online Access: http://dx.doi.org/10.1139/e82-089; http://www.nrcresearchpress.com/doi/pdf/10.1139/e82-089

In northern Manitoba, intersecting grooves 300–1800 m long are ice-scour marks created by the dragging of iceberg keels along rises in the bed of a glacial lake whose water plane was at about 305 m asl. The lake was bounded by glacial ice on its northern and eastern margins. The occurrence of scours on topographic divides indicates that a single extensive lake, thought to be a northern extremity of Lake Agassiz, occupied the area as far north as Seal River at the time the ice scours were formed. The lake extended as far west as Sprott Lake and eastwards into the Hudson Bay Lowlands into an area later occupied by Tyrrell Sea. The preservation of the scour marks suggests that the lake drained suddenly.Ice-scour marks are easily recognized on air photographs and provide a means of identifying areas that have been inundated by glacial lakes. Scours in emerged marine sediment are generally obliterated by littoral processes.