Swiss Journal of Geosciences volume , pages β Cite this article. Metrics details. 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 10 Be. Our results indicate at least two advances into the study area in Northwestern Switzerland; one during the LGM and one beforehand.
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. During the last glacial maximum LGM; The ice stream flowing northwards from the Mattertal Ice Plateau blocked the ice from the Rhone Ice Dome in the upper Rhone Valley and forced it to flow southwards and over the Simplon Pass.
This flow regime also explains the absence of erratic boulder lithologies from the upper Rhone Valley in the Swiss Midlands and the Jura Mountains Bini et al.
The Jura Mountains, made of Mesozoic carbonates Pfiffner , formed a barrier perpendicular to the ice flow, thus forcing the Valais Glacier to divide into two lobes. One flowed westwards and was joined by the Arve glacier, ending ca. The last advance of the Alpine glaciers onto the Foreland is morphologically and chronologically well defined Bini et al. Its maximum extent dated to Beyond the LGM extent, erratic boulders of Alpine origin and relict tills are also found.
These lines of evidence show that Alpine glaciers must have covered the Alpine Foreland and parts of the Jura Mountains once or several times prior to the LGM e.
