Browsing Radiocarbon, Volume 30 (1988) by Issue Date
Now showing items 1-20 of 38
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LaboratoriesAmerican Journal of Science, 1988-01-01
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Microwave Oven Pretreatment of Carbonates for 14C Dating by Accelerator Mass SpectrometryA microwave oven is used to pretreat carbonate samples prior to graphitisation and radiocarbon dating by accelerator mass spectrometry. The method reduces the risk of contamination of small carbonate samples and provides a fast and convenient method for the acid evolution of CO2.
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Radiocarbon, Volume 30, Number 1 (1988)American Journal of Science, 1988-01-01
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Radiocarbon, Volume 30, Number 2 (1988)American Journal of Science, 1988-01-01
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Radiocarbon, Volume 30, Number 3 (1988)American Journal of Science, 1988-01-01
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Radiocarbon Dating of Holocene Calcareous Tufa in Southern PolandCalcareous tufa from five sites in southern Poland, representing several most typical conditions of tufa sedimentation, were chosen for 14C, 13C, and 18O measurements. These tufas were deposited in a high-energy turbulent stream (the Raerawka site), in streams with moderate but variable flow (Rzerzusnia and Trzebienice), and in semilimnic conditions (Sieradowice site). Sediments of the Gliczarow site represent spring travertines. In all but the latter site, direct comparison of 14C dates of carbonate and organic fractions was possible, leading to an estimate of initial apparent age of carbonate sediments. Clear correlation was found between the value of initial apparent age of tufas and the hydrodynamic conditions of sedimentation. Corresponding values range from ca 3900 yr (Raetawka) to 910 yr for semilimnic sediments (Sieradowice). Intermediate, almost identical values, equal to 2460 +/- 200 yr and 2100 +/- 160 yr, were obtained for tufas from Rzerzusnia and Trzebienice, respectively. Detailed sedimentologic classification of tufaceous deposits is presented and some primary and secondary factors affecting the accuracy of radiocarbon dates of various types of tufas are also discussed.
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13th International Radiocarbon ConferenceAmerican Journal of Science, 1988-01-01
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Determination of Radon by Liquid Scintillation alpha/Beta Particle Spectrometry: Towards the Resolution of a 14C Dating ProblemTraces of uranium and radium within the 14C sample generate radon (Rn) which gets occluded during the benzene synthesis, thus generating false (extra) counts within the 14C counting window. This, if undetected, gives rise to erroneous 14C age determinations. The application of simultaneous alpha and Beta liquid scintillation spectrometry will enable a mathematical evaluation of the 14C signal unaffected by alpha and Beta particle emissions from radon decay daughters.
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The Relations Between Carbon Isotope Composition and Apparent Age of Freshwater Tufaceous SedimentsThis paper presents a synthetic approach to 14C dating of calcareous tufa, based on statistical analysis of correlations betwen lithologic type of tufaceous sediment, carbon isotope composition, and apparent age. Experimental data on several profiles from southern Poland and the United Kingdom reveal either constant or systematically changing values of apparent age. Constant value of apparent age in a profile can be attributed to calcareous muds precipitated from stagnant or low-energy water, and to tufas precipitated from turbulent water (oncoids, stromatolites, moss travertines) which are characterized by lack of significant correlation between delta-13C and 14C age of tufa carbonate. It was found that the relation between the apparent age of tufaceous sediment and delta-13C value of tufa carbonate depends on lithologic type of tufa. Phenomenological equations describing the dependence of apparent age upon delta-13C are given, and applied to estimate true ages of tufas from Gliczarow (southern Poland) and Folkestone (United Kingdom).
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Treatment of Discrepancies in Radiocarbon DatingA method is given for modifying the estimated radiocarbon dates of two samples when they are known to be in the wrong order.
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13th International Radiocarbon ConferenceAmerican Journal of Science, 1988-01-01