Constraints on the timing of debris-covered and rock glaciers: An exploratory case study in the Hólar area, northern Iceland

• Published in: Geomorphology
• Main Authors: Fernández-Fernández, José, Palacios, David, Andrés, Nuria, Schimmelpfennig, Irene, Tanarro, Luis, Brynjólfsson, Skafti, López-Acevedo, Francisco, Sæmundsson, Þorsteinn
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Spanish Ministry of Economy and CompetitivenessCGL2015-65813-RNils Mobility Program (EEA GRANTS)FPU programme (Spanish Ministry of Education, Culture and Sport)FPU14/06150Centre National de la Recherche Scientifique (CNRS)French National Research Agency (ANR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; Grjótárdalur; Hofsdalur; New Rock; Víðinesdalur; glacier; Iceland
• Online Access: https://hal.archives-ouvertes.fr/hal-03027332; https://hal.archives-ouvertes.fr/hal-03027332/document; https://hal.archives-ouvertes.fr/hal-03027332/file/fernandez-fernandez%20et%20al.%20accepted%20Iceland_rockglaciers_debris-covered.pdf; https://doi.org/10.1016/j.geomorph.2020.107196

International audience Eighteen samples for 36Cl Cosmic-Ray Exposure (CRE) dating were taken from glacially polished bedrocks, mo- raine boulders, fossil/active rock glaciers and debris-covered glaciers in Fremri-Grjótárdalur and Hóladalur cirques in the Víðinesdalur, Hofsdalur and Héðinsdalur valleys, close to Hólar village, in the Tröllaskagi peninsula, northern Iceland. Boulder sampling was preceded by a study of the boulder stability with the twofold aim of: en- suring that the surfaces to be sampled were stable enough for the reliable application of CRE dating, and to better understand the relation between the glacier dynamics and exposition history. The results show that the glaciers which occupy the valleys in Tröllaskagi began their retreat around 16 ka. Later, the glaciers advanced again around 11 ka within the cirques, and small moraines were formed. Thereafter, these small glaciers retreated and evolved into rock glaciers as debris from paraglacial processes accumulated on the glacier surface. The fronts of these rock glaciers stabilized definitively shortly after their formation and became eventually fossil after the melting of their internal ice. New rock glaciers and debris-covered glaciers formed afterwards, which still have internal ice at present, although their current dynamics are mostly related to subsidence. The stabilization of these rock glaciers and debris-covered glaciers is dated to the period between 7 and 3 ka, although they may have been reactivated during cold neoglacial periods. This research demonstrates the potential interest in apply- ing CRE dating methods to debris-covered glaciers and rock glaciers to determine their origin, evolution and phase of cessation of internal movement until they finally lost their internal ice and became fossil.