The Ticino-Toce glacier system (Swiss-Italian Alps) in the framework of the Alpine Last Glacial Maximum

We present a new glacier chronology from one of the major end moraine systems of the Southern Alps.Timing and extent of the Last Glacial Maximum (LGM) advance of the Ticino-Toce glacier were reconstructed in detail based on landform relationships and surface exposure dating. 10Be and 36Cl ages from41 erratic boulders constrain the last maximum of the Ticino-Toce glacier to have lasted from 25.0 ± 0.9ka to 19.9 ± 0.7 ka. Over this period of ca. 5000 years the Ticino-Toce glacier underwent only minoroscillations, during which the glacier front remained close to its LGM maximum position. Underpinnedby our detailed geomorphological reconstruction, the ages further demonstrate that the Verbano piedmont lobe was significantly larger (about 200 km2) than shown on recent maps. A short-lived glacierreadvance around 19.7 ± 1.1 ka terminated internal to the LGM maximum margins. Collapse of theVerbano lobe must have set in soon after and final withdrawal from the foreland occurred no later than19 ka. The new Ticino-Toce chronology matches temporal constraints of major glacier systems emergingfrom adjacent Alpine accumulation areas. This points to in-phase glacier advances across the WesternAlps, apart from the southwestern massifs for which a slightly earlier reaching of the Late Pleistocenemaximum position of the Lyon lobe was shown recently. A two- potentially three-fold LGM advancestructure with intervening retreat intervals, as reported for two major amphitheatres (Garda, Tagliamento) to the east is distinctly not supported by our data for the Ticino-Toce glacier. This contrast inglacier behaviour between the central and eastern Southern Alps is ascribed to shifting precipitationpatterns after ca. 23e22 ka, away from southern to predominantly northwestern air flow and a greaterindependence of southerly moisture transport for the central Southern Alps.