The Younger Dryas Main Line on Leka, Norway, as determined from a high resolution digital elevation model derived from airborne LiDAR data

Abstract

The Main Line is a conspicuous late glacial erosive feature along parts of the Norwegian coastline. Although the shoreline has been much studied, the genesis of the ancient raised sea-level is still somewhat unaccounted for. In this study, the Main Line on Leka, Norway, is illuminated through a high resolution (1mpixel size) digital elevation model (DEM) derived from airborne LiDAR data. The DEM allows a detailed mapping of the shoreline's dimensions and actual distribution and hence provides an improved foundation for interpreting the pronounced features. A new method for estimating cliff degradation during shoreline formation is presented. The Main Line is found from 106–112masl on Leka. Varying platform morphology across the island points to different shore-eroding mechanisms. The shoreline is thought to be developed through the interaction of sea–ice processes and freeze–thaw mechanisms, where the former agent is considered to be of particular importance where the platforms are most levelled. A bulge on the outermost part of the shoreline features is described for the first time and interpreted as a consequence of freeze-on plucking. Mean platform widths range from 9–29m, while mean cliff degradation is estimated to be 140m3m−1. By adapting the age span of Main Line formation reported elsewhere, maximum erosion rates over 1Ma totals to 58km. The study sheds light on the Main Line's potential as a reference level when assessing postglacial landscape development and highlights the significance of episodic erosional events in cold climate regimes.