Variazioni oloceniche della Vedretta della Lobbia (Gruppo dell’Adamello, Alpi Centrali)

Holocene variations of the Vedretta della Lobbia (Adamello Group, Central Alps)

Abstract

Geomorphological, glacial geological, lichenometrical and dendrochronological studies have been carried on the Upper Val di Genova with the aim of reconstructing Holocene fluctuations of the Vedretta della Lobbia. Some moraines have been dated on the basin of iconographical documents and dendrochronological studies. This allowed the reconstruction of two lichenometrical curves for the groups Rhizocarpon geographicum and Aspicilia cinerea for the period 1864-1915 A.D. The growth rates are respectively, 0,5 mm/yr aod 1,7 mm/yr. The Larch colonisation times has been evalued at ahout 15 years. The maximum extention reached by the glacier during the Little Ice Age is marked by a moraine near the Malga Matarot bassa, at about 1790 m. The age of this moraine is comprised between 1645 A.D. and 1845 A.D. The maximum position of the same glacier during the Holocene has been determined at a slightly more advanced point (before 5310± 180 ¹⁴C years B.P.). An end moraine located about 100 m South of the Malga Matarot bassa, at about 1 790 m, marks the position reached by the glacier in the second half of the last Century. In the 2Oth Century, the Vedretta della Lobbia gradually retreated to its present position at about 2570m. Small phases of advance (or stability) have been identified through some moraines dating back the early 1890's and 1920's. The total tetreat, between 1864 and the present has been estimated at over 2000 m. When the glacier was at its maximum position during the Little Ice Age, the snowline was situated about 60 m below the present snowline (2950).