Lichenometric dating in southeast Iceland: The size-frequency approach

The age of recent deposits can be determined using an intrinsic characteristic of the lichen 'population' growing on their surface. This paper presents a calibrated dating curve based on the gradient of the size-frequency distribution of yellow-green Rhizocarpon lichens. The dating potential of this new curve is tested on surfaces of known age in southeast Iceland. This particular size-frequency technique is also compared with the more traditional largest-lichen approach. The results are very encouraging and suggest that the gradient can be used as an age indicator, at least on deposits formed within the last c. 150 years - and probably within the last c. 400 years - in the maritime subpolar climate of southeast Iceland. Using both lichenometric techniques, revised dates for moraines on two glacier forelands are presented which shed new light on the exact timing of the Little Ice Age glacier maximum in Iceland.