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

• Published in: The Holocene
• Main Authors: Mercier, Denis, Cossart, Etienne, Decaulne, Armelle, Feuillet, Thierry, Jónsson, Helgi Páll, Sæmundsson, Þorsteinn
• Format: Article in Journal/Newspaper
• Language: English
• Published: SAGE Publications 2012
• Subjects: Paleontology; Earth-Surface Processes; Ecology; Archeology; Global and Planetary Change; Iceland
• Online Access: http://dx.doi.org/10.1177/0959683612463104; http://journals.sagepub.com/doi/pdf/10.1177/0959683612463104; http://journals.sagepub.com/doi/full-xml/10.1177/0959683612463104

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 ( 14 C 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.