• 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
    • 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.
    • High-Resolution 14C Dating of Organic Deposits Using Natural Atmospheric 14C Variations

      Van Geel, Bas; Mook, Willem G. (Department of Geosciences, The University of Arizona, 1989-01-01)
      The occurrence of atmospheric 14C variations complicates calibration, ie, the translation of 14C ages into real calendar ages. The procedure of wiggle matching, however, allows very precise calibration, by matching known 14C variations with wiggles in the floating chronology. In principle, wiggle matching can also be applied to a series of 14C dates from organic (peat) deposits. Where, in general, 14C ages are required at short distances and on small samples, dating by 14C accelerator mass spectrometry (AMS) is required.