Is gravitational spreading a precursor for the Stífluhólar landslide (Skagafjörður, Northern Iceland)?

• Published in: Géomorphologie : relief, processus, environnement
• Main Authors: Coquin, Julien, Mercier, Denis, Bourgeois, Olivier, Feuillet, Thierry, Decaulne, Armelle
• Format: Article in Journal/Newspaper
• Language: English
• Published: Groupe français de géomorphologie 2016
• Subjects: landslide; DSGSD; Iceland; paraglacial; deglaciation; Holocene; glissement de terrain; Islande; paraglaciaire; déglaciation; Holocène; Skagafjörður
• Online Access: http://geomorphologie.revues.org/11295

In Iceland, the Late Weichselian deglaciation led to paraglacial topographic readjustments in the form of extensive deep-seated gravitational slope deformation (DSGSD) and large rockslope failures (landslides and rock-avalanches). Here we provide age estimates for the Stífluhólar landslide (Tröllaskagi Peninsula, Northern Central Iceland), which indicate that this occurred between the end of the Late Weichselian deglaciation (15-13 ka cal. yr. BP) and 8200 ± 1400 cal. yr. BP. Our surface observations also suggest that the Stífluhólar landslide was probably initiated by propagation and connection of DSGSD failure planes. This observation suggests that the DSGSD can act as a precursor for landsliding in paraglacial settings. However, further investigations are still required to fully assess the role of DSGSD as a landslide precursor, both at the local and at a regional scale. Comparisons with other examples of paraglacial rock slope failures in Northern Iceland and in the world suggest that DSGSD is not the main or sufficient precondition for large landslides. The landslide of Stífluhólar occurred due to some combination of favorable preconditioning, predisposing and triggering controls. Predisposing controls include: the favourable dip of the bedding planes in the basaltic bedrock and the presence of intercalated poorly cohesive layers of palagonite between the lava layers, probably acting as basal sliding planes for the landslide. En Islande, la déglaciation du Weichselien tardif a conduit à d’importants réajustements topographiques paraglaciaires. Ces réajustements se déclinent sous la forme de processus de déformation du relief par étalement gravitaire (DSGSD) et de mouvements de masse (glissements de terrain et avalanches rocheuses). Dans cette étude, on apporte des éléments de datation au glissement de terrain de Stífluhólar, datations qui indiquent que celui-ci a été actif entre la fin de la déglaciation du Weichselien tardif (15-13 ka) et 8200 ± 1400 ans (âge calibré). Nos observations de surface ...