The Toce-Ticino Ice conveyor belts during the Last Glacial Maximum

Abstract

The distribution of erratic boulders of the Toce-Ticino glacier network highlights the interaction between two major glacier systems in the Alps during the LGM. Boulders belong to the Toce catchment in the central-western part of the Verbano and in the Orta end-moraine systems. Boulders pertaining to the Ticino mountain basin characterized the eastern flank of the Verbano and the glacial deposits in the Ceresio system. The provenance of boulders yielded key information for determining glaciers’ palaeoflow. The resulting development of the glacier piedmont lobes can be ascribed to the asymmetric topography of the overall accumulation area, which favored the early spread of the Toce glacier, which flowed from the highest sector (>4000 m a.s.l.) but with a short path (< 100 km). This glacier blocked the larger Ticino glacier towards the east forcing its diffluence into the prealpine area of Ceresio, which was formerly ice-free. The dynamics of the Toce-Ticino glacier network during the LGM enlightens the role of the location of the accumulation areas in driving differential development of glaciers that can force nearby slower glaciers towards a different path.