Mareková Ľ., Lánczos T., Milovský R. & Lačný A., 2020: Stable isotopes and water chemistry in Čachtice Cave and Hladový prameň Cave in relation to karst topology, soil cover, and past land-use. Acta Geologica Slovaca, 12, 1, 23–33.

Stable isotopes and water chemistry in Čachtice Cave and Hladový prameň Cave in relation to karst topology, soil cover, and past land-use

Ľubica Mareková¹, Tomáš Lánczos², Rastislav Milovský¹ & Alexander Lačný^3,4

¹Earth Science Institute of the Slovak Academy of Sciences, Ďumbierska 1, 974 11 Banská Bystrica, Slovakia
²Department of Geochemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 15 Bratislava, Slovakia
³Department of Geology and Palaeontology, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 15 Bratislava, Slovakia
⁴State Nature Conservancy of the Slovak Republic, Little Carpathians Protected Landscape Area, Štúrova 115, 900 01, Modra, Slovakia

Abstract

The Čachtické Karpaty Mts. are the northernmost part of the Malé Karpaty Mts. The studied area belongs to the Čachtice Karst area built by Middle to Upper Triassic Wetterstein limestone and dolomite. The Hladový prameň and Čachtická caves represent two contrasting cave systems, which were formed along steeply dipping fault structures with N–S and NW–SE strikes, respectively. The stable isotopes of CO2 in water samples from both caves point to microbially produced soil CO2 as main source of carbon in dissolved bicarbonate. We observed lighter carbon in water of the Hladový prameň, probably due to thicker pile of decomposing leaf litter above the cave and thus more soil CO₂ production. The study of carbon isotopes in grasses and soils with different histories of land-use ruled out presence of grasslands dominated by C4 plant species producing heavier carbon. In speleothems, the lightest oxygen occurs in soda-straws, while in flowstones and helictites the oxygen is heavier due to evaporation prior to calcite crystallization. Dripwater sampled simultaneously in the Hladový prameň and Čachtická caves slightly differ, reflecting a lagged response to rainfall events due to much thicker overburden in the Čachtická Cave. According to chemical analyses, the spring water at the Hladový prameň Cave has developed in shallow circulating system within Wetterstein Limestone, without significant contact with underlying dolomites.

Key words: karst water, stable isotopes, tectonics, soil carbon, Čachtice Karst

Manuscript received: 2020-03-02

Revised version accepted: 2020-05-15