Le tracce glaciali nel Parco Nazionale d’Abruzzo (Appennino Centrale): Nota preliminare

The glacial traces in the «Parco Nazionale d’Abruzzo» area (Central Apennines): preliminary note

Abstract

In the mountainous area of the «Parco Nazionale d'Abruzzo», characterized by several massifs with maximum altitudes frequently above the 2 000 m, a large number of glacial traces can be observed. The examination of new evidence discovered and the re-examinatinn of those already known has permitted to reconstruct several distinct glacial events. In the studied area the cirques are the mostt frequent forms due to glacial modelling, even though other glacial remains like troughs and moraine deposits are found in association with them. In a number of places the existence of several episods of glaciation is provided by the occurence of a cirque stairway observed on the same slope. Starting from the more complete and best preserved local sequence an attempt was made to put into order all the other glacial traces. Correlations have been based on relative position and morphology of the cirques and the snow limits. As a result, it seemed likely to refer the observed evidence to four distinct events of glaciation. The first glacial event (pre-Würmian glaciation, probably Riss) is characterized by a snow limit situated about 1 340 meters a.s.l. and evidenced by few glacial forms in the massifs of Toppe del Tesoro, S. Nicola and the Meta Mountains. They consist of large badly preserved cirque-like depressions situated about 1 300-1 400 meters a.s.l. and moraine deposits whose position and distribution largely contrasts with the actual orographic configuration. During a new glacial advance (maximum würmian expansion) the snow limit rised to 1 560 m. Numerous are the traces relative to this advance, consisting in a large number of erosional forms, like cirques and glacial troughs, and morainic deposits which frequently preserve their original morphology forming lateral and frontal moraines. The third event (first late Würmian stage = first apenninic stage of FEDERICI, 1979) is characterized by a further rise of the snow limit now situated about 1 760 m. The evidences relative to this minor expansion consist only of erosional forms except one morainic deposit ricognized on the eastern side of the Meta Mountains. Effects relative to the fourth event (second late Würmian stage = second apenninic stage of FEDERICI, 1979) can be observed only in the reliefs situated North ouf the Sangro Vallcey and in the Meta Mountains, while in the other reliefs the snow limit, situated about 1 970 m, had already reached or passed the altitude of their highest peaks. A summary examination of the distribution and the morphological features of the glacial traces studied shows that the area South of the Sangro valley seems to have developed greater glaciers that the part of the studied area situated at the North of the same valley.