Studies about glacial geology and geomorphology of the Adamello Group have been carried out in recent years with particular attention to Holocene landforms and deposits. Till now the following valleys have been investigated: V. dell'Avio, V. Miller - Conca del Baitone, V. Narcanello and upper V. di Genova. Of the 20 glaciers present in the studied area, the Pisgana, Lobbia and Mandrone glaciers proved to be of particular interest. These are between the widest glaciers of the group and are all systems with northerm exposures. Late Pleistocene and Holocene tills have been differentiated on the basis of the sedimentological characters, lichen cover and development of soils, as well as weathering degree. Several Holocene moraines have also been identified. Several 14C dates were obtained from buried soils and peat in V. Narcanello and V. di Genova. The oldest date so far obtained in the Adamello Group is from the left side of V. Narcanello. A buried soil found at 2545 m a.s.I, between two lateral moraines, Late Glacial and Holocene respectively yielded an age of 6600 ± 100 14C yr BP (GX-14711) corresponding to 7569/7372 cal yr BP (according to STUIVER & REIMER, 1986). In the same area, at about 2470 m, two buried soils yielded dates bracketing a Neoglacial advance of the Pisgana Glacier. The first sample was dated to 3015 ± 75 14C yr BP (GX-14712) corresponding to 3350/3086 cal yr BP (maximum limiting age). It was collected from a soil developed on the cited Late Glacial moraine at about 2470 m and buried by a Holocene lateral moraine. The minimum limiting age for the Pigsana glacier advance was supplied by a soil buried in a depression at about 2600 m and supported by the same lateral moraine. It was dated to 2345 ± 125 14C yr BP (GX-14710), corresponding to 2706/2207 cal yr BP. In V. di Genova an end moraine deposited at about 1775 m a.s.I. supports a peat deposit, the base of which was dated to 5310 ± 180 1 C yr BP (GX-15319). It supplies a minimum limiting age for the moraine, probably of Holocene age. Calibrated according to STUIVER et alii (1986) the age is 6299/5919 yr BP.· The top of the same peat deposit directly underlies another end moraine. It produced an age of 1190 ± 75 14C yr BP (GX-15318), corresponding to 1230/1003 cal yr BP. This is a maximum limiting age for this moraine which testifies a glacier advance during the Middle Age or the Little Ice Age. A push moraine made up of peat was identified at about 1800 m near Malga Materot, in V di Genova. The ·top of this peat was dated to 200 ± 70 14Cyr BP (GX-15314) corresponding to 305/0 cal yr BP. This date indicates a glacier advance of the Little Ice Age. Glacier variations that occurred in the XIX century AD (Little Ice Age) have been identified on the basis of historical maps and photographs.
Variazioni glaciali oloceniche nel Gruppo del M. Adamello. Holocene glacial variations in the Adamello Group.
BARONI, CARLO;
1992-01-01
Abstract
Studies about glacial geology and geomorphology of the Adamello Group have been carried out in recent years with particular attention to Holocene landforms and deposits. Till now the following valleys have been investigated: V. dell'Avio, V. Miller - Conca del Baitone, V. Narcanello and upper V. di Genova. Of the 20 glaciers present in the studied area, the Pisgana, Lobbia and Mandrone glaciers proved to be of particular interest. These are between the widest glaciers of the group and are all systems with northerm exposures. Late Pleistocene and Holocene tills have been differentiated on the basis of the sedimentological characters, lichen cover and development of soils, as well as weathering degree. Several Holocene moraines have also been identified. Several 14C dates were obtained from buried soils and peat in V. Narcanello and V. di Genova. The oldest date so far obtained in the Adamello Group is from the left side of V. Narcanello. A buried soil found at 2545 m a.s.I, between two lateral moraines, Late Glacial and Holocene respectively yielded an age of 6600 ± 100 14C yr BP (GX-14711) corresponding to 7569/7372 cal yr BP (according to STUIVER & REIMER, 1986). In the same area, at about 2470 m, two buried soils yielded dates bracketing a Neoglacial advance of the Pisgana Glacier. The first sample was dated to 3015 ± 75 14C yr BP (GX-14712) corresponding to 3350/3086 cal yr BP (maximum limiting age). It was collected from a soil developed on the cited Late Glacial moraine at about 2470 m and buried by a Holocene lateral moraine. The minimum limiting age for the Pigsana glacier advance was supplied by a soil buried in a depression at about 2600 m and supported by the same lateral moraine. It was dated to 2345 ± 125 14C yr BP (GX-14710), corresponding to 2706/2207 cal yr BP. In V. di Genova an end moraine deposited at about 1775 m a.s.I. supports a peat deposit, the base of which was dated to 5310 ± 180 1 C yr BP (GX-15319). It supplies a minimum limiting age for the moraine, probably of Holocene age. Calibrated according to STUIVER et alii (1986) the age is 6299/5919 yr BP.· The top of the same peat deposit directly underlies another end moraine. It produced an age of 1190 ± 75 14C yr BP (GX-15318), corresponding to 1230/1003 cal yr BP. This is a maximum limiting age for this moraine which testifies a glacier advance during the Middle Age or the Little Ice Age. A push moraine made up of peat was identified at about 1800 m near Malga Materot, in V di Genova. The ·top of this peat was dated to 200 ± 70 14Cyr BP (GX-15314) corresponding to 305/0 cal yr BP. This date indicates a glacier advance of the Little Ice Age. Glacier variations that occurred in the XIX century AD (Little Ice Age) have been identified on the basis of historical maps and photographs.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
