Chronology of deglaciation based on Be-10 dates of glacial erosional features in the Grimsel Pass region, central Swiss Alps

Surface exposure dating, using in situ produced cosmogenic Be-10, is applied to determine the time since deglaciation of bedrock surfaces in the Grimsel Pass region. Nine Be-10 dates from bedrock surfaces corrected for cover by snow are minimum ages for deglaciation of the pass. Four 10 Be dates from surfaces below 2500 meters above sea level (m a.s.l.) on Nagelisgratli, east of Grimsel Pass, yield ages that range from about 14 000 to 11 300 years. Three Be-10 dates from locations above 2600 m a.s.l. on Nagelisgratli are between about 11 700 and 10 400 years. Two 10 Be dates from locations at 2560 m a.s.l. below Juchlistock are about 12 100 and 11 000 years. The geographical distribution of Be-10 dates on Nagelisgratli either may show the timing of progressive deglaciation of Grimsel Pass or may reflect differences in subglacial erosion of bedrock in the pass region. All dates are discussed in the context of deglaciation of the late Wurmian Alpine ice cap and deglaciation from Last Glacial Maximum (LGM) ice extents in other regions.