Geologic map of Sicily (after (after DEL FRATI et al., 2000, modified), with the indication of the main mountain districts: Peloritani (siliceous metamorphites), Nebrodi (flysch, some schists and limestones), Madonie (alkaline rocks, quartzitic sandstones, clays), Etna (volcanic rocks), Sicani (sandstones, limestones, gypsum), Hyblaean Plateau (limestones), Erei (sandstones, marls, gypsum, clays).