Naslov
Modern Calibration of a Speleothem Oxygen Isotope Record Analyzed by SIMS in Postojna Cave (Slovenia)

Autori
Domínguez-Villar, David ; Lojen, Sonja ; Krklec, Kristina ; Kozdon, Reinhard ; Valley, John W.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
KR7 Climate Change: The Karst Record. Scientific Programme and Abstracts / Drysdale, R. ; Hellstrom, J. ; Woodhead, J. - Melbourne : Melbourne University Press, 2014, 69-69

Skup
Climate Change: The Karst Record 7th International Conference KR7 "Down Under"

Mjesto i datum
Melbourne, Australija, 29.09.2014. - 03.10.2014

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
paleoclimate ; Postojna Cave ; SIMS ; speleothem banding

Sažetak
The interpretation of proxy records from speleothems is generally based on numerous assumptions. The calibration of the recent portion of the speleothem records with instrumental records of climate or other environmental variables minimizes these assumptions and refines their proxy interpretations. Here we present the calibration of the oxygen isotope record of a stalagmite top from Postojna Cave (Slovenia). The top 500 micrometers of the stalagmite PO2 were analyzed by SIMS (Secondary ion mass spectrometry). We provided a continuous 18O record with a spatial resolution of 14 micrometers. To evaluate the analytical reliability, the record was triplicated. Confocal and ultraviolet microscope imaging were used to characterize the speleothem banding and to locate the analytical spots within the bands. The monitoring of the cave hall microclimate where PO2 was collected and its drip water isotope values together with its drip rate have been also studied in order to understand the nature of the banding. We found an outstanding similarity between the recorded oxygen isotope speleothem signal and the weighed mean annual record of oxygen isotopes in precipitation at the nearby IAEA station of Ljubljana. The speleothem is able to capture the same amplitude as the mean annual weighed isotope values of precipitation, suggesting that the residence time is close to one year. Although the speleothem is laminated, we do not find a significant intra-annual seasonality in the speleothem record. This is in agreement with the drip water oxygen isotope monitoring study carried out in this site. Thus, the drip water isotope record shows an inter-annual variability with no clear seasonality. This lack of seasonal pattern in the calcite isotope record is recorded not just during the calibrated period, but also in lower sectors of the speleothem, with slightly different laminated patterns and growth rates. The high resolution study of the oxygen isotope signal at the top of PO2 stalagmite demonstrates that the isotope signal of this speleothem is a reliable record of the oxygen isotope composition of precipitation in the region, and that cave processes do not modify the variability of the averaged oxygen isotope composition in precipitation. Finally, we can conclude that due to the residence time of the water at the aquifer, the speleothem signal does not represent a seasonally biased record of oxygen isotope values in precipitation.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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