Geomorfologia delle valli del Rio delle Pozze e del Torrente Motte (Abetone, Appennino Tosco-Emiliano)

Geomorphology of the Rio delle Pozze and Torrente Motte valleys (Abetone, Tuscan-Emilian Apennines)

Abstract

An accurate knowledge of present and past geomorphological processes in an area of the Tuscan-Emilian Apennines near Abetone was achieved in this study, also by elaborating a geomorphological map at a 1:10,000 scale. In this territory, prevalently characterised by arenaceous rock types and, secondarily, by argillaceous and silty ones, the landforms listed below were recognised. – Structural landforms: the most evident are located near the Apennines watershed, where the slope face corresponds to the stratum surface of the Macigno Sandstones and where there are structural scarps more than 30 m high. – Glacial landforms and deposits: they include cirques, overdeepened hollows, roches moutonnées and moraine ridges. – Cryogenic and nivation landforms and deposits: among these, block fields, nivation hollows, avalanche tracks and cones, protalus ramparts, block streams and gelifluction deposits should be mentioned. – Gravity-induced slope landforms and processes: besides the presence of particularly developed scree slopes, various types of mass movements have been recognised, such as earthflows, falls and topples, translational slides, rotational and roto-translational slides, as well as deep-seated gravitational slope deformations (Dgsd), the latter characterised by a dominant structural control (NW-SE and SW-NE oriented faults). – Landforms, processes and deposits due to running waters: slopes affected by rill wash, colluvial and alluvial fans, related to concentrated running waters, are present together with swampy deposits filling small structural depressions; moreover, two orders of alluvial terraces, badland forms, debris flows and small waterfalls have been surveyed. Since the hydrographic network is in a deepening stage, present alluvial deposits are found only upstream of the numerous wiers that dam the courses of the Pozze and Motte torrents. – Anthropogenetic landforms and deposits: among Man’s activities which modify the landscape, the construction of large parking areas and ski tracks should be mentioned; these kinds of activities have produced slope cuts and filling of some small swampy areas. The data acquired allowed geomorphological events to be reconstructed starting from late Upper Pleistocene. In particular, in this sector of the Northern Apennines glacial traces ascribable only to the glaciation known in the Alps as Würm III were found. An attempt to reconstruct a relative chronology of the stadial phases was also carried out, thus identifying forms related to Apennines Stage I, which was characterised by two distinct stages with snow limits respectively of 1,611 and 1,663 m a.s.l., and Apennines Stage II, also characterised by two phases with a snow limit ranging between 1,770 and 1,836 m. Apennines Stage III did not leave any trace since, according to the previous authors, its permanent snow limit would be found at heights superior to those of the Apennine peaks of this area. In general, the action of the various morphogenetic agents in the evolutive history of these valleys was strictly conditioned by the structural characteristics of the area.