Rapid age assessment of glacial landforms in the Pyrenees using Schmidt Hammer exposure dating (SHED)

Schmidt hammer (SH) sampling of 54 Be-10-dated granite surfaces from the Pyrenees reveals a clear relationship between exposure and weathering through time (n=52, R-2=0.96, P<0.01) and permits the use of the SH as a numerical dating tool. To test this Be-10-SH calibration curve, 100 surfaces were sampled from five ice-front positions in the Tet catchment, eastern Pyrenees, with results verified against independent Be-10 and C-14 ages. Gaussian modelling differentiates Holocene (9.4 +/- 0.6 ka), Younger Dryas (12.6 +/- 0.9 ka), Oldest Dryas (16.1 +/- 0.5 ka), last glacial maximum (LGM; 24.8 +/- 0.9 ka) and Wurmian maximum ice extent stages (MIE; 40.9 +/- 1.1 ka). These data confirm comparable glacier lengths during the LGM and MIE (similar to 300 m difference), in contrast to evidence from the western Pyrenees (>= 15 km), reflecting the relative influence of Atlantic and Mediterranean climates. Moreover, Pyrenean glaciers advanced significantly during the LGM, with a local maximum at similar to 25 ka, driven by growth of the Laurentide Ice Sheet, southward advection of the polar front, and a solar radiation minimum in the Northern Hemisphere. This calibration curve is available online (http://shed.earth) to enable wider application of this method throughout the Pyrenees.