Schmidt-hammer exposure-age dating (SHD) of snow-avalanche impact ramparts in southern Norway: Approaches, results and implications for landform age, dynamics and development

© 2015 John Wiley & Sons, Ltd. Schmidt-hammer exposure-age dating (SHD) was applied to the problem of dating the diachronous surfaces of five distal river-bank boulder ramparts deposited by snow avalanches plunging into the Jostedøla and Sprongdøla rivers in the Jostedalsbreen region of southern Norway. Approaches to local high-precision linear age calibration, which controlled in different ways for boulder roundness, were developed. The mean age (SHDmean) and the maximum age (SHDmax) of surface boulders were estimated for whole ramparts, crests and distal fringes. Interpretation was further assisted by reference to R-value distributions. SHDmean ages (with 95% confidence intervals) ranged from 520±270years to 5375±965years, whereas SHDmax ages (expected to be exceeded b