Efflorescences on weathered sandstone tors in the Stone Town Nature Reserve in Ciężkowice (the Outer Carpathians, Poland)-their geochemical and geomorphological controls.

The study area within the Stone Town Nature Reserve in Ciężkowice encloses a variety of occurrences of sandstone tors exposed within the Skała Hill (Rock Hill) from its top down into the Biała River Valley. The efflorescences of salt minerals on the walls of the sandstone tors represent end products of weathering. Several types of the efflorescences have been distinguished in relation to their distribution, the composition of the parent sandstones and local conditions of the natural environment. Laboratory methods have allowed identifying several sulphate minerals of various hydration (mainly pickeringite, hexahydrite, pentahydrite, alunogen, K-alum, gypsum, syngenite). They occur as two morphological varieties: as accumulations of a millimetre large flakes or as granules. The development, diversification and distribution of the efflorescences depend first of all on the rock moisture controlled by its capillary rise. The dampness of the lower tor parts is relatively the major factor; thus, such places are the sites favouring efflorescing phenomena. The presence of sulphur-bearing ions that are contained in salt minerals may be attributed to oxidation of pyrite occurring in the sandstone formations in the vicinity of Ciężkowice but may also be associated with local waters, more probably with mineral ones than with groundwater recharged by atmospheric precipitations. Air pollution, particularly with sulphur compounds, should also be considered in weathering of sandstone tors and the formation of the efflorescences.