The valley glacier network of the Valsugana (south-eastern Alps) during the LGM: Chronology and Equilibrium Line Altitudes 

Abstract

During the Last Glacial Maximum the Valsugana sector in the south-eastern European Alps was characterized by an extensive glacier network that included the large valley glacier belonging to the Adige glacier, through the transfluence in the Fersina area, and major tributaries from the Calamento and Cavè valleys. The glacier surface reached up to 1400 m a.s.l. in the western sector of the study area with a downstream gentle slope to the east. At Borgo Valsugana, the trunk glacier merged with several tributaries and flowed also towards the Tesino plateau to the east, where it merged with the tributary valley glacier. In the Tesino area, the glaciers flowed mainly to the south towards the major trunk glacier. This flowed downstream until Primolano, where the narrow reach of Canal del Brenta dammed its flow. The gorge promoted the bulging of the glacier front and its split into two lobes: the first to the south formed the lateral moraines of Enego and Col del Gallo ending with a seracs cascade; the second lobe to the east merged with the Cismon-Piave glacier. This latter was a major ice-field originated in the central Dolomites and reached its western frontal position above the Corlo gorge (Rossato et al., 2018).  In this articulate network several nunataks remained ice-free; here, lateral moraines with erratic boulders mark the elevation of the trimline. At Mt. Lefre, three boulders were dated to the LGM with exposure dating method (10Be). These are the first exposure ages for an LGM glacier in the south-eastern Alps and can be compared to radiocarbon chronologies from other glaciated valleys In the study area also independent glaciers (Mt. Agaro, Mt. Coppolo, Mt. Cavallara) developed. In the Prealps the large Altopiano dei Sette Comuni plateau glacier had a calculated Equilibrium Line Altitude (ELA) of 1680 m a.s.l. (Rettig et al., 2023), while the Monte Grappa ice cap had a calculated ELA of 1450 m a.s.l. (Baratto et al., 2003; Rettig et al., 2023). The ELA estimates allow insights into the climatic conditions under which the LGM glaciers in the Valsugana evolved.