Molluscan assemblages in Late Holocene tufa cones in the Pieniny Mountains (southern Poland)

Abstract

Limestone rock walls of various inclination form a favourable substrate for the deposition of calcareous tufas that form cone-shaped structures located at the foot of slopes or fill niches within them. Such carbonate deposits usually contain rich and diversified molluscan assemblages, whose composition and structure closely correspond to the ambient environmental conditions in the immediate vicinity. The study of the Pieniny Mountains area revealed 10 sites with such deposits. The identified malacofouna was subjected to detailed analysis. It enabled identification of three types of faunistic assemblages (Bythinella austriaca assemblage, Pyramidula pusilla assemblage, and a shade-loving species assemblage), which are related to the conditions prevailing during the deposition. Tufa cones found in the Pieniny Mountains represent the historic period (Late Holocene). The deposits provide a record of two climatic phases: warmer and colder. The former (Medieval Warm Period) involved the intensified deposition of carbonate material and the rapid growth of tufa cones. The latter – the Little Ice Age – entailed the slow degradation of cones and slower sedimentation of tufas, while the intensified physical weathering led to the increase in the clast material proportion (sharp-edged limestone fragments). Tufas accumulated in the zone unaffected by high anthropogenic pressure and thus represent a record of natural environmental changes during the historic period.