European Society for Isotope Research Isotope Workshop Volume ESIR 7th Workshop Seggauberg, June 27 - July 1 2004 Hosted by: Karl-Franzens University Department of Earth Sciences Geology and Paleontology & Landesmuseum Joanneum Department of Mineralogy Ber. Inst. Erdwissenschaften K.-F.-Univ. Graz Bd. 8 ISSN 1608-8166 Isotope Workshop Volume Graz 2004 Bojar, A.-V., Fritz, H., Bojar, H.-P., (Eds.): 7th Workshop of the Euro- pean Society for Isotope Research.- Ber. Inst. Erdwissenschaf- ten, Karl-Franzens Universität Graz, Band 8, 172 S., Graz, 2004. Herausgeber und Verleger: Institut für Erdwissenschaften, Bereich Geologie und Paläontologie, Karl-Franzens-Universität Graz, Heinrichstrasse 26, A-8010 Graz, Österreich Redaktion, Satz und Layout: Ana-Voica Bojar1, Harald Fritz1, Hans-Peter Bojar2 1 Institut für Erdwissenschaften, Bereich Geologie und Paläontologie, Heinrichstrasse 26, 8010 Graz. 2 Landesmuseum Joanneum, Abteilung für Mineralogie, Raubergasse 10, 8010 Graz. Druckerei: Offsetdruckerei der Karl-Franzens-Universität Graz, Cover: Xerox Steiermark Berichte des Institutes für Erdwissenschaften, Geologie und Paläontologie der Karl-Franzens-Universität Graz <ISSN 1608-8166> 2 ESIR VII European Society for Isotope Research Seggauberg Austria 27.6 – 1.7. 2004 Ber. Inst. Erdwissenschaften K.-F.-Univ. Graz Bd. 8 ISSN 1608-8166 Isotope Workshop Volume Graz 2004 Stable isotope study in a paleosol horizon of the Quaternary Vár-hegy travertine (Budapest, Hungary) Bernadett Bajnóczi1, László Korpás2 1Laboratory for Geochemical Research, Budaörsi út 45., H-1112, Budapest, Hungary, e-mail: [email protected] 2Hungarian Geological Institute, Stefánia út 14., H-1143 Budapest, Hungary, e-mail: [email protected] Beside the classic geological (sedimentological) and geomorphological studies, the investigation of travertines in Hungary recently turned to the geochemical analysis of sediment material and determination of possible links between geochemistry and lithofa- cies. Geochemical data, mostly stable C and O isotope compositions of Quarternary tra- vertines occurring at several places in Hungary were recently published by Kele et al. (2003) and Földvári et al. (2003). Quarternary travertine occurrences sometimes contain paleosol horizons which are result of former subaerial exposure periods. The study of paleosol horizons is very impor- tant in reconstructing past environmental conditions. We studied the paleosol horizon intercalated into the travertine of the Vár-hegy (Castle Hill) in Budapest. One of the methods applied was stable isotope analysis of car- bonate phases of the paleosol. Results were compared to the stable isotope composition of travertine, because comparison of data may indicate the amount of carbonate of pedogenic origin in the paleosol, thus providing information about the stage of development of pe- dogenesis. The Quaternary sequence of the Vár-hegy starts with basal clastic strata, which are overlain by travertine. The lower part of the travertine is laminated, muddy and rich in ter- restrial and freshwater fossils and plants. The top of the laminated travertine is a subaerial unconformity surface, on which a paleosol layer of 15 to 50 cm thickness was developed. The paleosol horizon has a great lateral extension (200 to 400 m) and is covered by a 7 to 8 m thick massive travertine poor in fossils and plants. The basal layer of paleosol is made of calcareous muddy sediments covering the karstic surface of travertine. The main level of paleosol consists of two horizons macroscopically; the lower one is richer in carbonate: ESIR VII European Society for Isotope Research Seggauberg Austria 27.6 – 1.7. 2004 3 Ber. Inst. Erdwissenschaften K.-F.-Univ. Graz Bd. 8 ISSN 1608-8166 Isotope Workshop Volume Graz 2004 grains are penetrated and surrounded by white, thin and loose calcareous coatings and fi- bers at some places. Microscopic observations on the paleosol and calcareous cavity fills revealed that they are mostly made up of mechanically reworked travertine clasts with a variable amount of allothigenic siliciclastic (e.g. quartz, mica and rock) fragments. Traces of carbonate reprecipitations can also be detected in thin sections: needle-fiber calcite in vugs and pores and micritic carbonate precipitations (hypocoatings) around pores of the paleosol and cav- ity fills. These secondary carbonate precipitations can result from biogenic processes dur- ing pedogenesis, therefore may indicate the possible influence of vegetation during their accumulation. Bulk carbonate samples of paleosol and cavity fills (which do not contain secon- dary carbonate visible to the naked eye), paleosol samples rich in secondary carbonate and pure secondary carbonate precipitations were analysed for stable isotope composition. The oxygen isotope composition of the Vár-hegy travertine is between -17.7 and -13.7‰ (rela- tive to V-PDB), while its carbon isotope composition has a narrow range from 1.1 to 2.1‰ (Földvári et al., 2003). Pure secondary (pedogenic) carbonate precipitations have signifi- cantly different isotope compositions (average: δ13C = -7.3‰, δ18O = -7.1‰) compared to that of the travertine (Fig. 1). Paleosol samples rich in secondary carbonate have interme- diate isotope compositions between travertine and secondary precipitations, which indicate that they are mixtures of these two endmembers (Fig. 1). Isotope composition of bulk paleosol and cavity fill samples partly overlaps with that of the travertine, but half of the samples have slightly lower δ13C values (Fig. 1). Re- sults indicate that bulk paleosol and cavity fill samples contain no or only minor amount of pedogenic carbonate. The amount of pedogenic carbonate can be estimated from the car- bon isotope composition of the two endmembers (Nordt et al., 1998). Calculations show that bulk paleosol contains up to 16%, whereas bulk cavity fill contains up to 25% pe- dogenic carbonate. Stable isotope results indicate that formation of authigenic carbonate is subordinate in the bulk paleosol material, which points to a weak in situ pedogenesis. Carbon isotope composition of pure secondary carbonate suggests that during pedogenesis the flora was mostly composed of C3-type plants. 4 ESIR VII European Society for Isotope Research Seggauberg Austria 27.6 – 1.7. 2004 Ber. Inst. Erdwissenschaften K.-F.-Univ. Graz Bd. 8 ISSN 1608-8166 Isotope Workshop Volume Graz 2004 4 2 δ18O (‰, V-PDB) 0 δ -20 -18 -16 -14 -12 -10 -8 -6 13 C (‰, V- -2 -4 PDB) travertine -6 bulk cavity fill bulk paleosol paleosol rich in secondary carbonate -8 pure secondary carbonate -10 Fig. 1. Oxygen vs. carbon isotope composition (in ‰ relative to V-PDB) of bulk paleosol and cavity fill samples, paleosol samples rich in secondary carbonate and pure secondary (pedogenic) carbonate precipitations from the paleosol horizon of the Vár-hegy travertine. The isotope composition of the Vár-hegy travertine is mostly from Földvári et al. (2003). References Földvári, M., Berner, Zs., Stüben, D., 2003. Thermoanalytical study of Quaternary thermal lacustrine travertine occurrences in Hungary (Buda-Vár-hegy, Budakalász, Szomód-hegy). Acta Geologica Hungarica 46/2, 195-204. Kele, S., Vaselli, O., Szabó, Cs., Minissale, A., 2003. Stable isotope geochemistry of Pleis- tocene travertine from Budakalász (Buda Mts, Hungary). Acta Geologica Hunga- rica 46/2, 161-175. Nordt, L. C., Hallmark, C. T., Wilding, L. P., Boutton, T. W., 1998. Quantifying pedogenic carbonate accumulations using stable carbon isotopes. Geoderma 82, 115-136. ESIR VII European Society for Isotope Research Seggauberg Austria 27.6 – 1.7. 2004 5 Ber. Inst. Erdwissenschaften K.-F.-Univ. Graz Bd. 8 ISSN 1608-8166 Isotope Workshop Volume Graz 2004 Isotopic investigation on the origin of the mineral waters from Someşeni, România Petre Berdea1, Stela Maria Cuna1, Gabriela Balas1, Călin Baciu2 1National Institute of Research and Developement for Isotopic and Molecular Technologies, Donath Str. 71-103, POBox 700, Cluj Napoca, Romania, e-mail: [email protected] 2Babeş-Bolyai University, Kogălniceanu Str. 1, Cluj-Napoca, Romania, e-mail: [email protected] The isotopic study (18O, D) of mineral waters from Someşeni Spa is important in the tentative to reabilitate them as natural curative waters. The studied area, Someşeni Spa, is located in the eastern part of Cluj-Napoca, Romania. From a geological point of view, the mineral aquifer is located on the western border of the Neogene Transylvanian Basin. The therapeutical qualities of this waters were known since the early 1920's and the spa was established in 1927. The first scientific studies on the mineral waters from Someşeni were completed in the early 1920's with some researches on their chemical composition and medical properties.The detailed physical and chemical analyses were performed by the Institute of Balneology and Physioterapy (Institute of Balneology and Physioterapy, 1965). From the hydrologycal point of view, our researches by deuterium analyses have presumed that these waters are related to a unique aquifer, and the differences in the physical and chemical properties of the sources are related to the different ways in which these waters are followed in the vicinity of the salt body (Baciu et al., 2001). The water samples were collected monthly for five investigated springs: No. 1, No. 2, No. 3, No. 8, No. 15 , and also for Becaş Brook and Someşul Mic River. The deuterium analyses of water are carried out on the hydrogen gas obtained by on line quantitative reduction of water sample (about 1 µl