Cryogenic cave calcite from several Central European caves: age, carbon and oxygen isotopes and a genetic model

Abstract

Cryogenic cave calcite (CCC), formed by segregation of solutes during water freezing, was found in three Central European caves. This calcite type forms accumulations of loose calcite grains on cave floor. The calcite grains are of highly variable crystal morphology, and of sizes ranging from less than 1 mm to over 1 cm. The most typical feature is their accumulation as loose (uncemented) crystals. U-series dating indicates the formation of CCC in the studied caves during several climatic oscillations of the Weichselian (between 61 and 36 ka BP in the Chelsiowa Jama–Jaskinia Jaworznicka cave system in Poland, between 34 and 26 ka BP in the BUML Cave in the Czech Republic, and between 26 and 21 ka BP in the Stratenská Jaskyňa cave system, Slovakia). At the time of CCC formation, the studied caves were lying in a periglacial zone. Detailed C and O stable isotope study of CCC samples revealed that slow water freezing under isotope equilibrium was the dominant formational process in the studied Polish and Czech caves. Significantly higher δ 13C values of CCC in the Stratenská Jaskyňa Cave indicate either water freezing in a more opened system with continuous CO 2 escape (Rayleigh fractional separation), or participation of another CO 2 source. The model of slow water freezing under isotope equilibrium is supported by isolated character of the caves having limited ventilation. In contrast, modern cryogenic cave calcite powders sampled directly on the ice surface of two recently iced caves in Slovakia with high ventilation showed much higher δ 18O and δ 13C data, similar to cryogenic calcites obtained in experimental rapid water freezing.