Multiple advances of Alpine glaciers into the Jura Mountains in the Northwestern Switzerland

Abstract

To reconstruct the timing of Alpine glacier advances onto the Jura Mountains, we sampled 17 Alpine erratic boulders within and beyond the LGM (Last Glacial Maximum) extent of the Valais Glacier along three transect for the analysis of cosmogenic 10Be. Our results indicate at least two advances into the study area in Northwestern Switzerland; one during the LGM and one beforehand. Reaching of the maximum extent of by the Valais Glacier into the Jura mountains during the LGM occurred at 21.9 ± 1.8 ka based on erratic boulders exposure ages. Ages of boulders located beyond the LGM extent of the Valais Glacier vary from 19.9 ± 1.6 to 144.0 ± 9.6 ka. These ages indicate that many of the boulders were displaced and re-deposited by local ice in the Jura Mountains both during and perhaps even prior to the LGM. Therefore, the chronology of the pre-LGM advance(s) of Alpine glaciers into the Jura Mountains remains still to be elaborated.