Timing of retreat of the Reuss Glacier (Switzerland) at the end of the Last Glacial Maximum

Abstract

We used cosmogenic 10 Be and 36 Cl to establish the timing of the onset of deglaciation after the Last Glacial Maximum of the Reuss Glacier, one of the piedmont lobes of the Alpine ice cap that reached the northern Alpine foreland in Switzerland. In this study, we sampled erratic boulders both at the frontal position in the foreland (Lenzburg and Wohlen, canton Aargau) and at the lateral Alpine border position (Seeboden moraine, Rigi, canton Schwyz). The minimum age for the beginning of retreat is 22.2 ± 1.0 ka at the frontal (terminal) position and 20.4 ± 1.0 ka at the lateral position. These ages are directly comparable with exposure ages from the other piedmont lobes in the northern Alpine foreland. Our data from the mountain called Rigi, do not support the hypothesis that boulders located external to the Seeboden moraine were deposited prior to the last glacial cycle. We present a first exposure age from an erratic boulder in a retreat position in the Alpine foreland. The Reuss Glacier was approximately 12 km behind the maximal extent no later than at 18.6 ± 0.9 ka.

A deglaciation model of the Oberhasli, Switzerland

“…It then retreated and readvanced to a similar extent during a second culmination phase and remained there until 19 ka. Similarly, piedmont lobes in Italy and in the northern Alpine foreland had abandoned their outermost LGM positions by no later than 24 ka (Ivy‐Ochs et al ., ; Gianotti et al ., , ; Akçar et al ., ; Reuther et al ., ; Federici et al ., ; Ravazzi et al ., ; Reber et al ., ; Ivy‐Ochs, ). By no later than 19–18 ka, ice had completely disappeared from the northern forelands and had withdrawn to behind the mountain front (Lister, ; van Husen, ; Reitner, ; Ivy‐Ochs et al ., ).…”

Timing and flow pattern of the Orta Glacier (European Alps) during the Last Glacial Maximum

“…Major culminations of Alpine glaciers (blue banners) during the LGM from selected end‐moraine systems compared to the Orta chronology (Reuss after Reber et al . ; Orta: this work; Garda after Monegato et al . ; Rhine after Preusser et al .…”

“…Such an occurrence of multiple phases during the end of the LGM has been widely reported for many endmoraine systems throughout the Alps (e.g. Ivy-Ochs et al 2004a;Monegato et al 2007Monegato et al , 2017Ravazzi et al 2014;Reber et al 2014;Salcher et al 2015). Constraining the time gap between subsequent advances has however proven to be difficult and, moreover, this length seems to vary between Alpine regions.…”

“…These include the Reuss (Reber et al . ), Ivrea (Gianotti et al . , ) and Rivoli‐Avigliana (Ivy‐Ochs et al .…”

“…During the Late Pleistocene cold phases, the European Alps hosted large glacier systems whose chronologies have been continuously updated (Preusser 2004;Heiri et al 2014; Ivy-Ochs 2015; Monegato & Ravazzi 2018). From this perspective, the history of the Alpine glaciers during the Last Glacial Maximum (LGM, 26.5-19 ka according to Clark et al 2009 or 30-16.5 ka after Lambeck et al 2014) has been assessed through stratigraphical and geomorphological studies in many Alpine end-moraine systems, which yielded new chronological constraints for the maximum ice extents (Jorda et al 2000;Monegato et al 2007Monegato et al , 2017Gianotti et al 2008Gianotti et al , 2015Akc ßar et al 2011;Preusser et al 2011;Ravazzi et al 2012;Reber et al 2014;Salcher et al 2015;Federici et al 2017;Ivy-Ochs et al 2018) and deglaciation phases (Fontana et al 2014;Ravazzi et al 2014;Scapozza et al 2014;Reitner et al 2016;Wirsig et al 2016). On the other hand, remarkable differences in glacier development and size exist between the northern and western sectors of the Alps, where large piedmont lobes spread onto the forelands, and the glaciers on the eastern and southern sides, where glaciers for the most part remained confined within the valleys ( Fig.…”