KARST LANDSCAPES IN SICILY (SOUTHERN ITALY), WITH EXAMPLES OF SUSTAINABLE EXPLOITATION

In Sicily karst is very important to landscape evolution related to the large extension of soluble rocks and the climate conditions. Karst develops both in carbonate rocks, outcropping in the NW sector of the Apennine chain and in the foreland area, and in evaporites which characterize the Central and the Southern areas of the Island.

Karst in carbonate rocks affect mainly Meso–Cenozoic platform limestones and, subordinately, Mesozoic slope to basin dolomitic limestones with intercalations of marls and siliceous rocks. Landscapes are characterized both by structurally-controlled karst landforms (fluviokarst valleys, caves; polje and dolines developed in depressions produced by tectonics or by selective erosion) and by karst landforms not controlled by structure (karst planation surfaces). In the foreland area fluviokarst canyons and horizontal caves prevail.

Gypsum karst is well developed and shows different kinds of landscape according to the large extension of Messinian evaporite outcrops and the different geological and environmental settings. Surface karst landforms show a large variety of typologies, ranging in size from a few microns to some kilometres. Among the medium and large sized landforms, dolines represent the most typical forms, though blind valleys, polje-like depressions, canyon, subsidence and collapse lacustrine basins in rock overlying gypsum occur as well.

Gypsum caves reflect the features of classic gypsum karst system under unconfined conditions consisting of different levels of low-gradient galleries at different elevations, connected through shafts.

In gypsum and carbonate areas it is possible to distinguish two mechanisms of karstification linked respectively to stillstand phases (karst sub-planar surfaces, galleries) and to lowering phases of the karst base-level (deep caves, canyon, shafts). These mechanisms have favoured, in the same areas, processes of prevailing lateral (stillstand phases) or vertical (lowering phases) erosion.

Karst areas in Sicily represent extraordinary environments for their original landscapes and for the observation and study of the solution forms. The Sicilian Region Authority has already set up some natural reserves mostly linked to the presence of caves or peculiar landforms and landscape.