Lateglacial and Holocene glacier variations in an active volcanic area, northern Jan Mayen (Nord-Jan), Norway

Abstract

Jan Mayen is a volcanic island situated 550 km NE of Iceland. It has been shown previously that the island and probably also shallow shelf areas around it were covered by a contiguous ice cap during the last glaciation. Today, active glaciers exist only in the northern part of the island around the Beerenberg volcano. Until now, information on Lateglacial and Holocene glacier and environmental variations has been sparse. We focus on the northern part (Nord-Jan), discussing glacier evolution and environmental changes from the Lateglacial to the Holocene. Widespread volcanic activity during the postglacial era resulted in lava flows and volcanic craters amidst glaciogenic deposits, complicating glacial and environmental reconstructions. We suggest that the ice cap covering Jan Mayen separated into two (northern and southern) approximately 20 ka ago, based on observations from glacial striae and terrestrial cosmogenic nuclide exposure dating. Deglaciation of the southern flank of the Beerenberg ice cap was accelerated by initial subglacial volcanic activity, which probably rapidly evolved to protrude above the glacier surface. Subsequently, around 18.9 ka, vertical melting and ice-marginal recession intensified in Nord-Jan. A relatively warm period followed thereafter, evidenced by organic material giving a calibrated age of 17 to 16 cal. ka BP. The extent of deglaciation during this period is unknown as the dated material was found redeposited in lake sediments. Several cosmogenic exposure ages from bedrock and glacial erratics correspond to the Lateglacial period. The interpretation of these ages is not obvious, but we favour a hypothesis involving a Lateglacial readvance of the glaciers when lateral moraines were also deposited. Mild conditions, characterized by plant growth and soil formation, prevailed during the Early Holocene. During this period, the lateral moraines formed during the Lateglacial probably disintegrated, leaving only the remnants visible today.