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Abstract:
GLACIOLOGICAL AND CLIMATOLOGICAL STUDIES IN ICE-CAVES OF MONCODENO (NORTH GRIGNA, PROVINCE OF LECCO, LOMBARDY) - The existence of perennial ice and snow deposits in the karst shafts of the Moncodeno area, at altitudes of about 1800 to 2100 m a.s.l, has long been known. Even so, no detailed study has been formerly carried out. Three ice and snow cores have been drilled in the glaciated cave environment and chemical, isotopic, crystallographic and textural analyses were carried out on them. By linking these observations with the morphology, stratigraphy and internal structures of the deposits, and with the hypogean and epigean climate records, we were able to identify the accumulation processes and to give one upper and some lower limits to the age of these deposits. The most notable deposit shows a more than 15 m thick succession of clear-ice layers, found at a depth of about 80 m and suspended between two shafts in the cave "Abisso sul margine dell'Alto Bregaia” Because of the relative position to the cave entrance, no snow can reach this deposit. The crystallographic and textural features, confirmed by the chemical and isotopic trends, show that this is lake-ice. At present no accumulation can be observed and the top surface is now at least 3 m lower than it was three decades ago. The underlying shaft, deglaciated at some time in the past by the air circulation drains the water so that hypogean lakes can no more develop. We have found sound stratigraphic and glaciotectonic evidences of at least three accumulation and three ablation phases. When compared to local present precipitations and to the values available from literature, the ice chemical composition and 6110 values show that this ice must be younger than the end of the last ice age, while preceding the beginning of industrial activity related contributions.