Rich and diverse molluscan assemblages have been found in calcareous tufa exposed in the valley of the Skalski stream in the Pieniny Mountains. 59 samples representing 10 profiles were subjected to malacological analysis. Very rich malacofauna (over 20 000 specimens belonging to 78 species) was the basis for carried out reconstruction. Three faunistic assemblages differing in composition and structure, as well as age, were separated. The oldest of them (the assemblage with shade-loving species) is characteristic of forest habitats and corresponds to the Middle Holocene (Atlantic Phase). Two younger assemblages (the assemblage with open-country species and the assemblage with Bythinella austriaca) represent historical period. The first of the mentioned is characteristic of the agricultural zones subjected to strong anthropogenic impact on the environment, mainly deforestation. The second one is typical of areas with unfavourable terrain conditions which are therefore not used for agricultural purposes. Such a diversity in malacocenosis allows the assessment of the degree of anthropogenic changes to the environment and of the intensity of anthropogenic impact on the environment.