Lichenometry in Iceland, results and application

• Published in: Géomorphologie : relief, processus, environnement
• Main Author: Decaulne, Armelle
• Format: Article in Journal/Newspaper
• Language: English
• Published: Groupe français de géomorphologie 2016
• Subjects: thalles de rhizocarpon; datation; géomorphologie; rhizocarpon thallus; dating; geomorphology; geo; envir; Dater; Mýrdalsjökull; Vatnajökull; Iceland; Islande
• Online Access: http://journals.openedition.org/geomorphologie/11291

This paper proposes a review of the use of lichenometry in Iceland since 1970, using different techniques to solve the chronology of geomorphic processes. Most users have sought to date proglacial landforms in two main areas: around the southern ice-caps of Vatnajökull and Mýrdalsjökull and in the Tröllaskagi peninsula in the north. Based on the results of over 35 published studies, lichenometry has been widely applied in Iceland, proposing numerical ages (absolute dating) and relative ages (relative dating) of different surfaces. Increasing awareness of methodological limitations of the technique, together with more sophisticated data processing, has led some authors to claim that lichenometric 'ages' are robust and reliable. However, the different measurement techniques used make it difficult to compare regions or studies in the same area. These problems are exacerbated in Iceland by rapid environmental changes across short distances and more generally by lichen species mis-identification in the field. Moreover, the reliability of lichenometric dates is discredited by their lack of correspondence with tephrochronologic data, whatever the lichenometric method used. Finally, the accuracy of lichenometry quickly weakens after few decades of surface exposure and the method loses rapidly any absolute aptitude. At the end, absolute dates proposed in the literature are not very trustworthy, and lichenometry should be used for relative dating only. Cet article propose un examen des utilisations de la lichénométrie en Islande depuis 1970, différents auteurs ayant mis en place plusieurs techniques pour résoudre des questions de chronologie des processus géomorphologiques. La plupart des utilisateurs ont cherché à dater les formes proglaciaires dans deux secteurs principaux : aux marges des calottes glaciaires Vatnajökull et Mýrdalsjökull au sud et dans la péninsule de Tröllaskagi au nord. A partir des résultats proposés par plus de 35 publications, la lichénométrie a été largement appliquée en Islande, proposant des ...