Late Holocene Climatic Change in the Balkans: Speleothem Isotopic Data from Serbia
Issue Date
2001-01-01Keywords
Ceremosjna Cavestalagmites
Serbia
O 18 O 16
diagenesis
climate change
cave environment
oxygen
terrestrial environment
solution featuresspeleothemscalciteYugoslaviaSouthern Europeisotope ratiosHoloceneupper HolocenecorrelationpaleoclimatologyEuropeCenozoicQuaternaryC 14carbondatesisotopesradioactive isotopesC 13 C 12stable isotopesabsolute agegeochemistrycarbonates
Metadata
Show full item recordCitation
Kacanski, A., Carmi, I., Shemesh, A., Kronfeld, J., Yam, R., & Flexer, A. (2001). Late Holocene climatic change in the Balkans: Speleothem isotopic data from Serbia. Radiocarbon, 43(2B), 647-658.Journal
RadiocarbonDescription
From the 17th International Radiocarbon Conference held in Jerusalem, Israel, June 18-23, 2000.Additional Links
http://radiocarbon.webhost.uits.arizona.edu/Abstract
A detailed profile of the stable isotopes of carbon and oxygen was obtained from a speleothem (stalagmite) from the Ceremosjna Cave in eastern Serbia. The stalagmite is a low magnesian calcite that did not show any evidence of diagenetic alteration. It was precipitated under isotopic equilibrium conditions from dripping water. The age and rate of deposition was derived from six internally consistent radiocarbon dates. The initial 14C activity was determined to be approximately 80 pMC. The stalagmite appears to preserve a continuous record of calcite deposition from approximately 2300 BP until the present. Oxygen isotopic data, based upon 100 samples, are used to derive the first paleotemperature record for Serbia. A regression analysis of the all the data indicates that over the period of time that the speleothem was deposited there was a general trend of lowering of the average temperature. Superimposed upon this are significant long-term temperature fluctuations. These can be divided into four broader climatic groupings. Going from the oldest times to the present, there are two warm periods separated by a period when the temperatures fell below the temperature trend line. However, the absolute temperatures were generally above those of the more recent period that is generally characterized by the coolest climatic conditions.Type
Proceedingstext
Language
enISSN
0033-8222Scopus Count
Collections
Related items
Showing items related by title, author, creator and subject.
-
Iron-Manganese System for Preparation of Radiocarbon AMS Targets: Characterization of Procedural Chemical-Isotopic Blanks and FractionationWe report a practical system to mass-produce accelerator mass spectrometry (AMS) targets with 10-100 micrograms carbon samples. Carbon dioxide is reduced quantitatively to graphite on iron fibers via manganese metal, and the Fe-C fibers are melted into a bead suitable for AMS. Pretreatment, reduction and melting processes occur in sealed quartz tubes, allowing parallel processing for otherwise time-intensive procedures. Chemical and isotopic (13C, 14C) blanks, target yields and isotopic fractionation were investigated with respect to levels of sample size, amounts of Fe and Mn, pretreatment and reduction time, and hydrogen pressure. With 7-day pretreatments, carbon blanks exhibited a lognormal mass distribution of 1.44 micrograms (central mean) with a dispersion of 0.50 micrograms (standard deviation). Reductions of 10 micrograms carbon onto targets were complete in 3-6 h with all targets, after correction for the blank, reflecting the 13C signature of the starting material. The 100 micrograms carbon samples required at least 15 h for reduction; shorter durations resulted in isotopic fractionation as a function of chemical yield. The trend in the 13C data suggested the presence of kinetic isotope effects during the reduction. The observed CO2-graphite 13C fractionation factor was 3-4% smaller than the equilibrium value in the simple Rayleigh model. The presence of hydrogen promoted methane formation in yields up to 25%. Fe-C beaded targets were made from NIST Standard Reference Materials and compared with graphitic standards. Although the 12C ion currents from the beads were one to two orders of magnitude lower than currents from the graphite, measurements of the beaded standards were reproducible and internally consistent. Measurement reproducibility was limited mainly by Poisson counting statistics and blank variability, translating to 14C uncertainties of 5-1% for 10-100 micrograms carbon samples, respectively. A bias of 5-7% (relative) was observed between the beaded and graphitic targets, possibly due to variations in sputtering fractionation dependent on sample size, chemical form and beam geometry.
-
On Correcting 14C Ages of Gastropod Shell Carbonate for FractionationCorrecting the 14C age of a sample for fractionation is straightforward if the measured carbon was derived entirely from the atmosphere, either directly or through chemical and/or biological reactions that originated with atmospheric carbon. This correction is complicated in the case of gastropods that incorporate carbon from limestone or secondary carbonate (e.g. Soil carbonate) during shell formation. The carbon isotopic composition of such gastropod shells is determined by fractionation, as well as mixing of carbon from sources with different isotopic values. Only the component of shell carbonate derived from atmospheric carbon should be corrected for fractionation. In this paper, the author derives a new expression for correcting the measured 14C activity of gastropod shells for fractionation, and describe an iterative approach that allows the corrected 14C activity and the fraction of shell carbonate derived from atmospheric carbon to be determined simultaneously.
-
Comparison of Vanadium Oxide Catalysts for Synthesis of Benzene: Benzene Purity, Yields and Reconditioning MethodsThis study compares vanadium oxide catalysts from three different sources: Noakes (N), Harshaw Chemical (H) and Kh. Arslanov at the St. Petersburg State University, Russia (R). The catalysts are used to convert acetylene to benzene in the last step of benzene synthesis. The organic purity of benzene in all three catalysts is high; 99.91-99.93% for (N) and (H) and 99.87% for (R). The benzene yields range from 90.0 to 94.3%. (N) averaged 92.6%, (H) averaged 91.1% and (R) averaged 92.0%. A conversion residue in the catalysts was analyzed for delta-13C and found to be isotopically lighter relative to acetylene by -2.2 per mil for (N) and (H) and -3.9 per mil for (R). Benzene yields were studied on different reconditioning methods applied to all catalysts: heating to 400 degrees C in air averaged 92.3%; the same temperature with a half and half mixture of O2 and Ar averaged 91.9%, adding a half and half mixture of H2 and Ar at 200 degrees C to the end of this treatment averaged 91.8%. Based on this research, the obvious difference seen between the catalysts is in their trace by-products.
