Volcanical and surficial process constraints on the formation of a lake basin in Jan Mayen, Norway

Abstract

The volcanic island of Jan Mayen, located in the Norwegian – Greenland Sea, has very few lake basins out of which only one, Lake Nordlaguna, holds a permanent lake throughout the year. The island is volcanic and has been glaciated, but the lake basin is not genetically typical for volcanic crater lakes or other common types of volcanic lakes. Nor is it typical for ice-scoured glacial lakes. Instead, the lake basin originated from a series of hydromagmatic and subglacial volcanic eruptions, which over time yielded an irregularly horseshoe-shaped chain of small mountains to form flanks of a bedrock basin. Potassium–Argon and Argon–Argon dates from these rock walls facing the lake yield ages ranging from about 564 to 21 ka. Subsequent glacier overriding only had a minor influence on the basin morphology, but contributed, as did other surface processes to its sediment infill. Following deglaciation, relative sea-level change led to the formation of a beach barrier that connects between the rock walls. Tectonic uplift recorded in sections and ground penetrating radar profiles around the lake perimeter and dated using radiocarbon and tephra geochemistry, is attributed to a historical eruption in 1732 CE that took place on the opposite side of the island, some 4–5 km away. The uplift blocked the last remaining passage between the basin and the ocean, leading to the present landlocked lacustrine environment.