Carta geomorfologica della Valle Desertetto (Alpi Marittime): note illustrative

Geomorphological map of the Valle Desertetto (Maritime Alps) and explanatory notes

Abstract

The geomorphological map of the Valle Desertetto is the result of a detailed field survey in an area representative of the main morphotypes present on the Italian side of the Argentera Massif. ‘The Valle Desertetto lies immediately above the valley of Gesso della Valletta Torrent. A step 190 m high links the two valleys, but there is no surface water flow to the main valley. The absence of a water course dissecting the valley bottom is a distinctive element of this geographical unit, as is the presence, in the medium-high section of the valley, of dolines and swallow-holes, mantled by a glacial deposit. Three glacial cirques are carved into the diatexitic rocks of the valley head. From the threshold of these two morainic frontal ridges extend. Inside the easternmost cirque a small but typical rock glacier can be observed. A transfluence is likely to have occured from the adjacent Valle Stura di Demonte through the Colle dell’Arpione, to the east of which the left slope, made of calcareous and slaty rocks, is located, where outwash processes are prevalent, favoured by the absence of trees, On its eastern side this slope is characterized by clear structural scarps, due to the tectonic structure of the sedimentary cover, On the right slope, instead, there are conditions of biostasy, with a prevalence of inactive forms such as rock channels and block fields/streams. This latter slope is partly mantled by a till deposit, left by the glacier snout of the main valley during the stag of its maximum expansion. The valley bottom, finally, is occupied by a fluvioglacial deposit, the surface of which does not show any trace of later carving. Anthropic impact is evident in the areas subject to quarrying. The waste material of this activity, affected by rill erosion, is involved in the slope dynamics. The cartographical representation of the forms, deposits and processes here described and of other less important ones, represents a methodological essay, a preliminary trial aimed at producing a smaller scale map comprising the whole basin area.