Oxygen Isotope Composition Snapshot of Spring Waters in a Karstified Plateau

In the period of September 10–21, 2002, 317 km² of Muránska planina karstic plateau (Slovakia) was mapped for springs in great detail. Within this short time interval, 295 springs were documented and also sampled for δ¹⁸O. Although only freshwater of apparently similar origin was sampled, δ¹⁸O was in a range between −10.90 and −7.32 ‰. Plateau is moderately vertically exaggerated (~400 to ~1400 m a.s.l.), but altitudinal differences do not explain this wide oxygen isotope span. Patterns of δ¹⁸O distribution were examined for the possible influence of documented springs’ parameters (temperature, discharge, electric conductivity, geology, aquifer circulation type, morphology around spring’s orifice) without finding any significant dependency. The main reason for very different δ¹⁸O values in nearby groundwater sources was identified in individual groundwater circulation regimes. According to IAEA GNIP stations’ records, a significant contrast in precipitation δ¹⁸O values was found within 14 months previous to the sampling. Heavier oxygen isotopes in the sampled set (around −8 ‰) probably reflect quick circulation influenced by enriched July–August 2002 precipitation (−5.28 ‰). Depleted δ¹⁸O in springs (around −10 ‰), corresponding to the impact of winter 2001/2002 precipitation (−18.4 to −14.7 ‰), suggests longer residence times.