Reconstructing chronology of post-glacial mass movements in the Skagafjörður, Northern Iceland (Northern Iceland) from radiocarbon, tephrochronological and geomorphological results

• Main Authors: Mercier, Denis, Decaulne, Armelle, Cossart, Etienne, Feuillet, Thierry, Sæmundsson, Þorsteinn, Jónsson, Helgi Páll
• Other Authors: Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Laboratoire de Géographie Physique et Environnementale (GEOLAB), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut Sciences de l'Homme et de la Société (IR SHS UNILIM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université Paris-Sorbonne (UP4)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Náttúrustofa Norðurlands vestra (NNv), Ríkisins, Sveitafélag Skagafjarðar
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2012
• Subjects: Post-glacial mass movements; Skagafjörður; Tephrochronological results; Geomorphologicalr esults; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; [SHS.GEO]Humanities and Social Sciences/Geography; Iceland
• Online Access: https://hal.science/hal-00661003

International audience Since the last major deglaciation, about 12-10,000 years ago, paraglacial landforms widely occurred in fjord and mountain areas; mass movements such as rock-slope failure, rock avalanches, rockslides, sackungs, etc., are common (Dikau et al., 1996; Ballantyne, 2008). In north Iceland, numerous mass movements' landforms occurred, mostly in areas within Tertiary basalt formation, in a landscape characterized by steep slopes and overdeepened glacial valleys. Many of those landforms can be observed in the Vestfirðir peninsula, in central North Iceland, and in Eastern Iceland. Jónsson (1957) made some early descriptions of such landforms. He concluded that most of those landforms were formed during or shortly after the last deglaciation, in Early Holocene; at the time of these first observations, results on absolute dating were lacking. Recently, several landslides have been studied in the Skagafjörður area (Decaulne et al., 2010, Mercier et al., 2011). The aim of this study is to date several landslides in the Skagafjörður area, by combining several proxies, e.g. radiocarbon dating, teprhochronology, raised beaches. We present here the result on one of those, the Höfðahólar case-study. - The material originating from the Höfðahólar rock avalanche partly buried a succession of raised beaches. Raised beaches out in the Skagi peninsula, just west of the study area, exceeding 65 m a.s.l., have been dated older than 12,000 yr B.P. (Rundgren et al., 1997). Beaches between 43 and 50 m a.s.l. have been dated to 11,300-9,900 yr B.P. and beaches at 22-31 m a.s.l. between 9900 and 9600 yr B.P. Regression below the present sea level occurred at 9,000 yr BP. As the rock avalanche deposit does not display visible evidence of being impacted by the glacio-isostatic rebound, it is believed to be younger than 9,000 yr B.P. - Tephra layers, occurring in a peat bog on top of the rock avalanche material date the avalanche older than 4,500 yr B.P., as the H4 tephra layer is found at 140 cm depth. - 14C dating of ...