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4. An early Holocene age for the Vatn landslide (Skagafjörður, central northern Iceland): insights into the role of postglacial landsliding on slope development

Author

Decaulne, Armelle, Etienne, Cossart, Mercier, Denis, Thierry, Feuillet, Coquin, Julien, Jónsson, Helgi Páll, Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-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)-Centre National de la Recherche Scientifique (CNRS), Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), and Université de Nantes (UN)-Université de Nantes (UN)

Subjects
ComputingMilieux_MISCELLANEOUS, Geomorphology analysis, [SHS]Humanities and Social Sciences
Abstract

International audience

Published
2016

6. Focusing on the spatial nonstationarity of landslide predisposing factors in Northern Iceland. Do paraglacial factors vary over space?

Author

Feuillet, Thierry, Coquin, Julien, Mercier, Denis, Cossart, Etienne, Decaulne, Armelle, Jónsson, Helgi Páll, Náttúrustofa Norðurlands vestra (NNv), Ríkisins, Sveitafélag Skagafjarðar, and Decaulne, Armelle

Subjects
[SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2014

7. Impacts of post glacial rebound on landsliding at a regional scale in Northern Iceland (Skagafjörður): spatial distribution and mechanisms involved

Author

Cossart, Etienne, Mercier, Denis, Decaulne, Armelle, Feuillet, Thierry, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn, 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), 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-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), Náttúrustofa Norðurlands vestra (NNv), and Ríkisins, Sveitafélag Skagafjarðar

Subjects
glacio-isostatic rebound, paraglacial, Iceland, Geomorphology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology
Abstract

International audience; Paraglaciation has often been considered as a main predisposing factor in landslide occurrence; its consequences have been particularly well identified at a fine scale (especially on bedrock jointing). However, the impacts of paraglaciation on hillslope dynamics at a regional scale have never been discussed. We focus here on the Skagafjörður area (Northern Iceland) to compare the role of paraglaciation with that of classic factors (topography, lithology etc.) in landslide occurrence, using a spatial analysis (based upon a chi-square test). The results highlight that landslides are over-represented in areas where post-glacial rebound was at its maximum (i.e. there is a concentration of landslides in the northern part), which fits well with the first chronological benchmark we obtained. Thus, landslides occurred during the first half of the Holocene, when the post-glacial uplift was at its maximum. Finally, the mechanisms that link post-glacial rebound and landsliding are discussed. On the one hand, post-glacial rebound is identified as an efficient process to generate slope instabilities, leading to a concentration of landslides in the northern part of the fjord. On the other hand, the expected role of glacial debuttressing cannot be demonstrated here, although it is often considered one of the most important paraglacial influences on landsliding.

Published
2013

8. Toward a comprehensive paraglacial model: case studies from Iceland

Author

Mercier, Denis, Cossart, Etienne, Decaulne, Armelle, Feuillet, Thierry, Coquin, Julien, Bourgeois, Olivier, POCHAT, Stéphane, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn, 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-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), 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), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Náttúrustofa Norðurlands vestra (NNv), Ríkisins, Sveitafélag Skagafjarðar, Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA)

Subjects
landslide, paraglacial, Iceland, geomorphology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography
Abstract

International audience; From the end of the Weichselian period and during the early Holocene, the landscape in Iceland underwent major changes. During this short-time interval, while glaciers were retreating from the lowlands, an exacerbation of geomorphic activity is noticed, due to lowering of the relative sea level, large glacial rivers flooding from the retreating ice margins and hillslope debutressing. As a consequence, many of the major paraglacial landforms that carved the Icelandic landscape are still visible nowadays. Two kinds of early Holocene paraglacial landforms can be identified in Iceland: (i) paraglacial denudation landforms (some slope failure deposits such as sackungs, rock avalanches and various other landslide types...), and (ii) paraglacial deposition landforms (alluvial fans, terraces, valley-train deposits, outwash plains or "sandurs" with outburst floods or "jökulhlaups", coastal deposits...). By using the sediment cascade framework, several paraglacial sources and sinks are also identified. This classical geomorphological approach privileges forms, processes to typify their temporal evolution through the Holocene. Some post-little ice age analogues in Iceland are also clear examples of such paraglacial evolution. To those external paraglacial dynamics we also propose to couple the consequences of the deglaciation to the internal earth dynamics (such as seismicity and volcanism, i.e. internal paraglacial effects). All around Iceland, glacio-isostatic rebound can explain the formation of numerous raised beaches, deltas, and strandflats. Also, an intense volcanic activity phase occurred within the early Holocene in Iceland, highlighting a link with the ice pressure release on the magma transfer. Based on our own researches and on literature review, we develop a spatial analysis at different time and space scales and propose a comprehensive paraglacial model, including external and internal earth dynamic implications.

Published
2013

9. Impacts of post-glacial rebound on landslide spatial distribution at a regional scale in northern Iceland (Skagafjörður)

Author

Cossart, Etienne, Mercier, Denis, Decaulne, Armelle, Feuillet, Thierry, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn, 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), Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-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)-Centre National de la Recherche Scientifique (CNRS), Náttúrustofa Norðurlands vestra (NNv), Ríkisins, Sveitafélag Skagafjarðar, Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), and Université de Nantes (UN)-Université de Nantes (UN)

Subjects
spatial analysis, para-glacial, Iceland, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography, post-glacial rebound, hillslope processes, mass movements
Abstract

International audience; In de-glaciated areas, para-glaciation (i.e. the conditioning of landscapes by prior glaciation) has often been considered a major predisposing factor in landslide occurrence; its consequences have been particularly well identified at a fine scale (especially on bedrock jointing). Hitherto, the relative impacts of para-glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically. We examine Skagafjörður area (northern Iceland) where landslides are widespread (at least 108 were mapped in an area of c. 3000km2).We compare the role of para-glaciation (debuttressing, influence of post-glacial rebound) with that of classic factors (topography, lithology, etc.) in landslide occurrence and location, using a spatial analysis based on a chi-square test. On the one hand, the results highlight that landslides are over-represented in areas where post-glacial rebound was at its maximum, with a stronger concentration of landslides in the northern part of the fjord. On the other hand, the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing. Tschuprow coefficient highlights that the influence of post-glacial rebound on landslide location is higher than the combined influence of slope gradient, curvature or geological structure. This result is supported by our initial evidence for the timing of landslides in the area: most landslides occurred during the first half of the Holocene, and a period of hillslope instability was initiated when the post-glacial uplift was at its maximum. Finally, the mechanisms that link post-glacial rebound and landsliding as well as the geomorphic impacts of landslides, are discussed.

Published
2013

10. The Vatn landslide, Skagafjördur, northern Iceland: evidence of an early Holocene paraglacial crisis and impact on further slope development

Author

Decaulne, Armelle, Mercier, Denis, Cossart, Etienne, Thierry, Feuillet, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn, Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-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)-Centre National de la Recherche Scientifique (CNRS), 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, Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), and Université de Nantes (UN)-Université de Nantes (UN)

Subjects
Mass movement, paraglacial geomorphology, Iceland, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography, déglaciation
Abstract

International audience; The Vatn landslide is of modest size (estimated to 830,000 m3), and the deposit exhibits poor spatial dispersion and longitudinal runout. Its location in the Skagafjördur fjord, Northern Iceland (65 57,337'N, 19 23,900'W), evidences slope post-glacial development in the area. The interest of this landslide is found lower contact: the downslope part of the landslide deposit bumps on a stripe of raised beach, trapping a flat area at its northernmost boundary. The contact between the slide and the beach is open by a deep anthropogenic ditch. Analysis of (i) stratigraphic sections along the ditch, (ii) log section openings in the flat area at the slide contact and (iii) onto the slide deposit, offer numerous dating elements. Lower pits are rich in organic material and tephra layers (the oldest one, H4, is dated to 4,260 cal. BP), while the upper pit revealed little accumulation over the slide deposit surface, exhibiting only tephra layers separated by poor organic units. The combination of radiometric method and geochemical analysis of the tephra layers results in a good time constrain for the landslide occurrence, before 9070 86 cal. BP and 8677 181 cal. BP (oldest tree remnants). Such results reinforce the hypothesis of a major paraglacial geomorphologic crisis at the early Holocene time, leading to numerous slope failures following the last glacial maximum retreat (Mercier et al., in press, The Holocene). The presence of the raised beach at the lower contact with the landslide seems to indicate an occurrence later than 11,000-11,400 cal. BP (intrapolated age of the raised beaches located at 22-31 m a.s.l.), and suggests that isostatic rebound is a relevant triggering factor (Cossart et al, in press, Earth Surface Processes and Landforms). The lower pit section encompasses the full Holocene period, exhibiting a succession of organic layers and a very poor accumulation in minerogenic material. Those 2 m (i) document the palaeoenvironmental settings throughout the Holocene with potentialities for palynology and diatoms analyses; (ii) shows the decoupling of slope processes triggered in the rockwall upper part from the lower slope, as during the last ca. 10,000 years, no minerogenic material was archived below the landslide deposit.

Published
2013

11. Impacts of paraglaciation on landsliding at regional scale in Northern Iceland (Skagafjörður): spatial modelling and mechanisms involved

Author

Cossart, Etienne, Mercier, Denis, Decaulne, Armelle, Feuillet, Thierry, JÓNSSON Helgi, Páll, Sæmundsson, Þorsteinn, 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), and Université de Nantes (UN)-Université de Nantes (UN)

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2013

12. The Höfðahólar rock avalanche (sturzström): chronological constraint of a paraglacial landsliding on an Icelandic hillslope

Author

Mercier, Denis, Etienne, Cossart, Decaulne, Armelle, Thierry, Feuillet, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn, 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-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), Náttúrustofa Norðurlands vestra (NNv), and Ríkisins, Sveitafélag Skagafjarðar

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2013

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

Author

Mercier, Denis, Decaulne, Armelle, Cossart, Etienne, Feuillet, Thierry, Sæmundsson, Þorsteinn, Jónsson, Helgi Páll, 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-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)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Université Clermont Auvergne (UCA)-Institut Sciences de l'Homme et de la Société (IR SHS UNILIM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), 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, Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), 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 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), and Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École Pratique des Hautes Études (EPHE)

Subjects
Post-glacial mass movements, Tephrochronological results, Geomorphologicalr esults, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography, Skagafjörður
Abstract

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 birches (Betula sp.) trunk, branch and root pieces found 80 cm deeper than the H4 layer provide 6,070 yr B.C. calibrated age. This period, around 8,000 yr B.P. is known as the "early birch periode" in Iceland, known to have been warm and favouring tree development (Einarsson 1991, Óladóttir et al. 2001, Langdon et al., 2010). Thus, the Höfðahólar rock avalanche event occurred between 9,000 B.P. (youngest beaches) and 8,000 B.P. (14C oldest dating). Such results comfort Jónsson idea, proposing the occurrence of such landslide as the result of a rapid paraglacial crisis following the deglaciation period, due to the combined effects of glacial oversteepening, supply water throughout the lava piles during glacial melting, and glacio-isostatic uplift.

Published
2012

14. The Orravatnsrustir palsa site in Central Iceland - Palsas in an aeolian sedimentation environment

Author

Sæmundsson, Þorsteinn, Ólafur, Arnalds, Christof, Kneisel, Jónsson, Helgi Páll, Decaulne, Armelle, Náttúrustofa Norðurlands vestra (NNv), Ríkisins, Sveitafélag Skagafjarðar, Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2012

15. Dating of a rock avalanche in Skagafjörður,, Northern Iceland: pieces of evidence of a paraglacial origin

Author

Mercier, Denis, Decaulne, Armelle, Cossart, Etienne, Feuillet, Thierry, Sæmundsson, Þorsteinn, Jónsson, Helgi Páll, 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, 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Université Clermont Auvergne (UCA)-Institut Sciences de l'Homme et de la Société (IR SHS UNILIM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École pratique des hautes études (EPHE), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and Mercier, Denis

Subjects
[SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO] Humanities and Social Sciences/Geography, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography
Abstract

International audience; The Skagafjörður area counts several large slope mass movements especially on the eastern side of the fjord. They are initiated from the top of the rockwall where a more or less developed scars are still observed. A significant number of those landforms have been described by Jónsson (1957), who interpreted those landforms as a result of post-glacial rockwall debuttressing, following the shrinking of the large ice bodies in the early Holocene. However, no attempt of dating has yet been carried out on the debris masses. The aims of this research are to discuss its possible paraglacial origin by combining four dating benchmarks: (i) the dating of a succession of raised beaches on which the rock avalanche material lies. The higher beaches, exceeding 65 m a.s.l., have been dated older than 12000 BP. Beaches between 43 and 50 m a.s.l. have been dated older than 11300 and 9900 BP and beaches at 22-31 m a.s.l. between 9900 and 9600 BP. Regression below the present sea level occurred about 9000 BP (Rundgren et al., 1997). As the rock avalanche deposit does not display visible evidence of being impacted by the glacio-isostatic rebound (no inherited sea cliffs are seen at higher elevation than the actual sea level), we estimate the rock avalanche occurred later than 9000 BP. (ii) the tephrochronological dating from the excavations made in the upper part of the mass, where peat areas developed since the setting of the rock avalanche goes back to 4500 years BP, with the H4 Hekla acid white thick layer found at 140 cm depth. The deposits from Hekla are well known in the area, and the five most common ash layers were discovered in the opened section, providing a significant time marker. (iii) 14C dating of birches (Betula sp.) trunk and branches pieces found 80 cm below the H4 layer. The results are not yet available, but the period around 8000 BP is considered at those latitudes as a warm period, favourable to tree development. (iv) basalt samples were collected on the rock avalanche deposit, at various elevations and settings on the deposit, to provide Cosmic Ray Exposure ages. To specify the age of the landslide, we will measure 10Be within the pyroxene minerals constituting the basalt. Beryllium isotopic ratios will be measured at the laboratory of CEREGE by Accelerator Mass Spectrometry. The results are in progress. Collectively, those chronological benchmarks constrain the trigerring of the rock avalanche event between 9000 BP (present-day sea-level) and 4500 BP (tephrochronology oldest dating). The finding of a large amount of wood long before the H4 tephra layer suggests that the occurrence of the rock avalanche was closer to the oldest extremity of this time period (so-called early birch period, just around 9000 BP, according to Einarsson 1991, and Óladóttir et al. 2001). Such results comfort the Ólafur Jónsson idea, proposing the occurrence of such mass movement as the result of a rapid paraglacial crisis following the deglaciation period, due to the combined effects of rockwall debuttressing and glacio-isostatic uplift. The cosmogenic and 14C results will provide a more accurate data for the chronological scenario. References Einarsson Þ., 1991. Geology of Iceland, rocks and landscape. Mál og Menning, Reykjavík, 309 p. Jónsson Ó., 1957. Skriðuföll og snjóflóð, Bókaútgáfan norðri, t. 1, 141 p. Óladóttir R., Schlyter P. & Haraldsson H., 2001. Simulating Icelandic vegetation cover during the Holocene, implication for long-term land degradation. Geografiska Annaler 83, 203-215. Rundgren M., Ingólfsson Ó., Björk S., Jiang H. & Hafliðason H., 1997. Dynamic sea-level change during the last deglaciation of northern Iceland. Boreas 26: 201-215.

Published
2011

16. Bergflóðið sem féll á Morsárjökull 20. mars 2007 - hverjar hafa afleiðingar þess orðið?

Author

Sæmundsson, Þorsteinn, Sigurðsson, Ivar, Pétursson, Halldór G., Jónsson, Helgi Páll, Decaulne, Armelle, Náttúrustofa Norðurlands vestra (NNv), Ríkisins, Sveitafélag Skagafjarðar, Náttúrufræðistofnun Íslands (NÍ), Government, Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
avalanche rocheuse, rock avalanche, [SHS.GEO]Humanities and Social Sciences/Geography, ComputingMilieux_MISCELLANEOUS
Abstract

National audience

Published
2011

17. The Hofdaholar rock avalanche in Skagafjörður,, Northern Iceland: geomorphological characteristics and relative dating, pieces of evidence of a paraglacial origin

Author

Decaulne, Armelle, Mercier, Denis, Cossart, Etienne, Feuillet, Thierry, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn, Laboratoire de Géographie Physique et Environnementale (GEOLAB), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Université Clermont Auvergne (UCA)-Institut Sciences de l'Homme et de la Société (IR SHS UNILIM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-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)-Centre National de la Recherche Scientifique (CNRS), 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, Université de Caen Normandie (UNICAEN), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-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), 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), 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), and Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École Pratique des Hautes Études (EPHE)

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2010

21. The Höfðahólar rock avalanche (sturzström): Chronological constraint of paraglacial landsliding on an Icelandic hillslope.

Author

Mercier, Denis, Cossart, Etienne, Decaulne, Armelle, Feuillet, Thierry, Jónsson, Helgi Páll, and Sæmundsson, Þorsteinn

Subjects
AVALANCHES, GEOMORPHOLOGY, LANDFORMS, PEAT, GLACIATION
Abstract

The Höfðahólar rock avalanche, in the Skagafjörður area of northern Iceland, was investigated on the basis of a geomorphological analysis of its landforms and close surrounding environment. Thanks to sound chronological constraints (14C dating from birch remnants in peat areas that developed within depressions over the chaotic rock-avalanche deposit, tephrochronological sequences resulting from subsequent ash fallouts over the deposit, calibration of an age–depth model of peats and previously dated raised beaches), we define the rock-avalanche implementation with a wider timeframe between 10,200 and 7975 cal. yr BP and with a narrower frame between 9000 and 8195 ± 45 cal. yr BP. Such a well constrained timing proposes one of the most precise datings of an early-Holocene major slope failure in Iceland. This result fits well in the known chronology of the deglaciation in this area and in the prevailing Icelandic theory of a generalized phase of landsliding that occurred shortly after the deglaciation of the area. The main driver for the rock-avalanche occurrence is associated to a paraglacial origin; glacio-isostatic rebound, associated to rockwall debuttressing, is thought to be the main factor in the genesis of this Boreal major disequilibrium. [ABSTRACT FROM AUTHOR]

Published
2013
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