• Gif Natural Radiocarbon Measurements XI

      Delibrias, Georgette; Guillier, Marie-Therese (American Journal of Science, 1988-01-01)
    • The Relations Between Carbon Isotope Composition and Apparent Age of Freshwater Tufaceous Sediments

      Pazdur, Anna (American Journal of Science, 1988-01-01)
      This 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).