Now showing items 21-26 of 26

    • Correcting 14C Histograms for the Non-Linearity of the 14C Time Scale

      Stolk, A.; Hogervorst, Koos; Berendsen, Henk (Department of Geosciences, The University of Arizona, 1989-01-01)
      Large numbers of 14C dates of the base and top of Holocene peat layers may be plotted in 14C histograms in order to establish statistically a chronology of periods of essentially elastic sedimentation and peat formation. Due to the non-linearity of the 14C time scale in terms of calendar years, clustering of 14C dates on random peat growth may occur. This seriously hampers the interpretation of histograms. A quantitative method and computer program were developed to correct the histograms for this effect. The correction factor that has to be applied depends on the calibration curve and the interval width of the correction parameter dy. For peat samples, an interval width of 100 14C yr and a calibration curve based on a 100-yr moving average seems to be a reasonable choice.
    • Corrected Calibration of the Radiocarbon Time Scale, 3904-3203 Cal BC

      De Jong, A. F. M.; Mook, Willem G.; Becker, Bernd (Department of Geosciences, The University of Arizona, 1989-01-01)
    • Anomalous AMS Radiocarbon Ages for Foraminifera from High-Deposition-Rate Ocean Sediments

      Broecker, W. S.; Trumbore, Susan; Bonani, Georges; Wölfli, Willy; Klas, Millie (Department of Geosciences, The University of Arizona, 1989-01-01)
      Radiocarbon ages on handpicked foraminifera from deep-sea cores are revealing that areas of rapid sediment accumulation are in some cases subject to hiatuses, reworking and perhaps secondary calcite deposition. We present here an extreme example of the impacts of such disturbances. The message is that if precise chronologies or meaningful benthic planktic age differences are to be obtained, then it is essential to document the reliability of radiocarbon ages by making both comparisons between coexisting species of planktomc foraminifera and detailed down-core sequences of measurements.
    • Accuracy and Precision in Dating Microgram Carbon Samples

      Vogel, J. S.; Nelson, D. E.; Southon, J. R. (Department of Geosciences, The University of Arizona, 1989-01-01)
      The accuracy of AMS radiocarbon determinations on very small samples has been tested by measuring a suite of microgram-sized samples of a known-age material. The total measurement precision for the smallest sample (50 micrograms) was found to be +/- 3% and the precision improved with larger sample size. The accuracies of the measurements were found to be within the measurement precisions