The clay mineralogy of Messinian sediments from several sections of Caltanissetta and Ciminna basins (Sicily) show the large extension of smectite facies in comparison with the under-and over-lying series (Tortonian, Pliocene). Messinian smectites are not related to the lithology (major and minor sequences, evaporites, tripoli, volcanic ash) and seem to be chiefly inherited from Messinian soils. Such an origin suggests a temperate-warm climate with contrasting wet and dry seasons. The rythmical character of the climate can contribute for explain the variable periodicity of Messinian deposits during the time.