Landforms and Landscapes of the Magdalen Islands: The Role of Geology and Climate

Abstract

The landscape and landforms of the Magdalen Islands are uniquely varied for such a small archipelago. Geomorphologically they are a part of the Maritime Plain which is located near the center of the Maritime Basin (375–325 Ma). The Magdalen Islands were pushed to the surface by salt-diapirs (~300 Ma). Formed by volcanic hills (basalt) surrounded by a low sandstone platform, the main islands are interconnected by late Holocene sand spits and tombolos. Located in the southern part of the Gulf of St. Lawrence, the Laurentide Ice Sheet (LIS) did not reach the Magdalen Islands during the last glaciation, but possibly much earlier (≥170 ka). Three different sets of geomorphological processes have impacted the landscape: structural, periglacial, and coastal. Sandstone platforms adjacent to volcanic hills are the structural controls. Superimposed on the sandstone platforms, cryopediments, ice-wedge pseudomorphs and dry valleys are the dominant periglacial landforms. Coastal landforms are dominated by cliffs, tombolos, and littoral spits. Perhaps the single most surprising fact is that eight islands with a cumulative area of 202 km2 can demonstrate such a remarkable variety of landscapes and landforms. The glacial record remains contentious.