Are Icelandic rock-slope failures paraglacial? Age evaluation of seventeen rock-slope failures in the Skagafjörður area, based on geomorphological stacking, radiocarbon dating and tephrochronology - HAL-SHS - Sciences de l'Homme et de la Société Accéder directement au contenu
Article Dans Une Revue Geomorphology Année : 2017

Are Icelandic rock-slope failures paraglacial? Age evaluation of seventeen rock-slope failures in the Skagafjörður area, based on geomorphological stacking, radiocarbon dating and tephrochronology

Denis Mercier
Julien Coquin
  • Fonction : Auteur
Armelle Decaulne
Etienne Cossart
Helgi Pall Jónsson
  • Fonction : Auteur
Þorstein Sæmundsson
  • Fonction : Auteur

Résumé

In Iceland there are numerous rock-slope failures, especially in the Tertiary basaltic formations of the northern, eastern and northwestern regions. The temporal pattern of rock-slope failures is fundamental for understanding post-glacial events. In the Skagafjörður district, central northern Iceland, 17 rock-slope failures were investigated to determine the age of their occurrence. A geomorphic survey was carried out to identify and characterize landform units, both on the rock-slope failures and in their immediate vicinity. In this coastal area, we used geomorphological stacking which included the relationship between rock-slope failures and raised beaches caused by glacial isostatic rebounds, the chronology of which was established in previous studies. We searched for depressions on the rock-slope failures to then excavate a series of pits and map the stratigraphy. The resulting stratigraphic framework was then validated using (i) radiocarbon dating of wood remains, and (ii) tephrochronology, both of which were complemented by age-depth model calibration. The results confirm that all the rock-slope failures potentially occurred before the Boreal (8 ka), while 94% occurred before the Preboreal (10 ka). They all potentially occurred after the glacial retreat following the maximal ice extent and the Preboreal. More precisely, 11 of them potentially occurred between the Preboreal and the first half of the Holocene. This study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase (debuttressing, decompression, glacial isostatic rebound, seismic activity, etc.), which are also controlling factors favouring landsliding, but are difficult to identify for each individual rock-slope failure.
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Dates et versions

halshs-01591969 , version 1 (22-09-2017)

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Denis Mercier, Julien Coquin, Thierry Feuillet, Armelle Decaulne, Etienne Cossart, et al.. Are Icelandic rock-slope failures paraglacial? Age evaluation of seventeen rock-slope failures in the Skagafjörður area, based on geomorphological stacking, radiocarbon dating and tephrochronology. Geomorphology, 2017, ⟨10.1016/j.geomorph.2017.08.011⟩. ⟨halshs-01591969⟩
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