Schmidt hammer exposure‐age dating: developing linear age‐calibration curves using Holocene bedrock surfaces from the Jotunheimen–Jostedalsbreen regions of southern Norway

Matthews, J. A. & Owen, G. 2009: Schmidt hammer exposure‐age dating: developing linear age‐calibration curves using Holocene bedrock surfaces from the Jotunheimen–Jostedalsbreen regions of southern Norway. Boreas, 10.1111/j.1502‐3885.2009.00107.x. ISSN 0300‐9483. The approach to calibrated‐age dating of rock surfaces using Schmidt hammer R‐values is developed, potential errors in dating Holocene rock surfaces are estimated and limitations are assessed. Multiple sites from glacially abraded bedrock outcrops of two ages (glacier forelands deglaciated for c. 100 years and adjacent late‐Preboreal terrain deglaciated for c. 9700 years) are used to analyse the variability of mean R‐values and to construct linear age‐calibration curves for three sub‐regions in the Jotunheimen–Jostedalsbreen regions of southern Norway. Conservative potential dating errors of 246–632 years are estimated using 95% confidence intervals associated with two control points, the width of the error limits being significantly greater for the Preboreal surfaces than for the younger Little Ice Age surfaces. Substantial improvements over previous age calibrations are largely attributable to the use of multiple sites as part of a research design that has effectively controlled for geological differences between the three sub‐regions. In the context of the Holocene time scale, the technique is seen as complementary to cosmogenic‐nuclide dating (which currently has lower precision) and lichenometric dating (which has a lower temporal range).