Geomorphic Evidence of Postglacial Terrestrial Environments on Atlantic Canadian Continental Shelves

• Published in: Géographie physique et Quaternaire
• Main Author: Shaw, John
• Format: Text
• Language: English
• Published: Les Presses de l'Université de Montréal 2005
• Subjects: Canada; glacier*; Newfoundland
• Online Access: http://id.erudit.org/iderudit/014752ar; https://doi.org/10.7202/014752ar

Changes in the geography of Atlantic Canada since the last glacial maximum (LGM) are grouped into three phases. The first phase (LGM – ca. 13 ka BP) commences with glaciers at the edge of the continental shelves, and ends with the glaciers having retreated to near modern coasts. In the second phase (ca. 13 ka BP‑10 ka BP), glaciers were mainly on land; on the continental shelves there were scattered small ice caps and an outer-shelf archipelago. Early in phase three, beginning ca. 10 ka BP, glaciers were largely absent, and the archipelago was gradually submerging; elsewhere, falling relative sea levels caused emergence. Multibeam sonar mapping has revealed the geomorphic evidence of submerged terrestrial environments of phases II and III, including fluvial, deltaic, and coastal systems. The best-preserved fluvial systems are in Northumberland Strait and the Bras d’Or Lakes. Elsewhere, multibeam bathymetric data allow discrimination between fluvial and non-fluvial channels. Deltas were mainly preserved in the special circumstances of Newfoundland fjords. Submerged coastal systems are common in the Bras d’Or Lakes, but rare elsewhere. Landscape preservation is ascribed to special circumstances. Paleogeographic reconstructions have applications in the field of evolutionary biology and archaeology. Les changements de la géographie du Canada atlantique depuis le dernier maximum glaciaire (DMG) sont regroupés en trois phases. La première (DMG, environ 13 ka avant le présent) débute au moment où les glaciers occupent le rebord des plates-formes continentales et se termine lorsqu’ils ont reculé jusqu’à proximité des lignes de rivage contemporaines. Pendant la deuxième phase (de 13 ka à 10 ka avant le présent), les glaciers se trouvaient principalement sur les terres; il y avait de petites calottes glaciaires éparses sur les plates-formes continentales et un archipel sur la partie extérieure des plates-formes. Au début de la troisième phase, il y a environ 10 000 ans, les glaciers étaient en grande partie absents et ...