Hostname: page-component-586b7cd67f-gb8f7 Total loading time: 0 Render date: 2024-11-26T18:59:53.914Z Has data issue: false hasContentIssue false
  • English
  • Français

The Effects of Contamination of Calcareous Sediments on their Radiocarbon Ages

Published online by Cambridge University Press:  18 July 2016

Dušan Srdoč ,
Nada Horvatinčić ,
Bogomil Obelić ,
Ines Krajcar-Bronić  and
Peg O'Malley
Dušan Srdoč
Affiliation:
Rudjer Bošković Institute, POB 1016, YU-41001 Zagreb, Yugoslavia
Nada Horvatinčić
Affiliation:
Rudjer Bošković Institute, POB 1016, YU-41001 Zagreb, Yugoslavia
Bogomil Obelić
Affiliation:
Rudjer Bošković Institute, POB 1016, YU-41001 Zagreb, Yugoslavia
Ines Krajcar-Bronić
Affiliation:
Rudjer Bošković Institute, POB 1016, YU-41001 Zagreb, Yugoslavia
Peg O'Malley
Affiliation:
United States Geological Survey, Denver, Colorado
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Two principal reasons for the inherent uncertainty in 14C dating of calcareous sediments such as tufa or those of lacustrine origin are the unknown initial 14C activity (Ao) of the sediment, mainly affecting younger (Holocene) samples, and contamination of older sediments with recent carbonate, causing 14C ages to be excessively young. To assess the contamination effect, samples of old tufa from the Riss/Würm interglacial were examined. These sediments contain essentially no 14C except that contributed by surface contamination. Tufa samples were crushed and grains ranging in size from <1 mm, 1 to 2mm, up to 4 to 5mm were separated for analysis; 2M HCl was then used to dissolve the samples in successive steps. 14C measurements indicated that each subsequent soluble fraction obtained from porous tufa gave a successively older age, indicating that the surface of the sample was contaminated by younger carbonates. No consistent effect of grain size on the 14C age was observed. Compact tufa proved to be less subject to contamination. 14C ages obtained on this material were also too young, yet older than the age obtained from porous tufa samples.

14C ages of interglacial tufa were cross-checked with the 230Th/234U dating method, using samples of very clean calcite which overlies the tufa blocks. Inferred 230Th/234U ages of the interglacial tufa (which had yielded 14C dates ranging from 25,000 to 37,000 yr) coincided with the last interglacial (Riss/Würm, Stage 5). Samples of Holocene tufa, in which contributions of recent 14C from surface contamination would pose less of a problem, yielded 14C and 230Th/234U dates which were in excellent agreement.

Type
IV. Methods and Applications
Information
Radiocarbon , Volume 28 , Issue 2A , 1986 , pp. 510 - 514
Copyright
Copyright © The American Journal of Science 

References

Eichinger, L, 1983, A contribution to the interpretation of 14C groundwater ages considering the example of a partially confined sandstone aquifer, in Stuiver, M and Kra, R S, Internatl 14C conf, 11th, Proc: Radiocarbon, v 25, no. 2, p 347–356.Google Scholar
Fontes, , Ch, J and Garnier, J M, 1979, Determination of the initial 14C activity of the total dissolved carbon: Water Resources Research, v 15, p 399–413.CrossRefGoogle Scholar
Geyh, M A, 1972, On the determination of the initial 14C content in groundwater, in Rafter, T A and Grant-Taylor, T, eds, Internatl 14C conf, 8th, Proc: Royal Soc New Zealand, Wellington, p D58–D69.Google Scholar
Horvatinčić, N (ms), 1985, Radiocarbon age measurements of tufa deposits from Plitvice lakes area (in Croatian with English summary); Ph D dissert, Univ Zagreb.Google Scholar
Krajcar-Bronić, I, Horvatinčić, N, Srdoč, D and Obelić, B, 1986, On the initial 14C activity in karst aquifers with short mean residence time, in Stuiver, M and Kra, RS, eds, Internatl 14C conf, 12th, Proc: Radiocarbon, this issue.Google Scholar
Mook, W G, 1972, On the reconstruction of the initial 14C content of groundwater from the chemical and isotopic composition, in Rafter, T A and Grant-Taylor, T, eds, Internatl 14C conf, 8th, Proc: Royal Soc New Zealand, Wellington, p 343–352.Google Scholar
Olsson, I, 1980, Progress in radiocarbon dating, promising techniques and trends in the research: Fizika, v 12 suppl 2, p 37–68.Google Scholar
Pearson, F J and Hanshaw, B B, 1970, Sources of dissolved carbonate species in groundwater and their effects on C-14 dating, in Symposium on isotope hydrology, Proc: IAEA, Vienna, p 271–285.Google Scholar
Srdoč, D, Breyer, B and Sliepčević, A, 1971, Rudjer Bošković Institute radiocarbon measurements I: Radiocarbon, v 13, p 135–140.Google Scholar
Srdoč, D, Horvatinčić, N, Obelić, B and Sliepčević, A, 1980, Radiocarbon dating of calcareous tufa; how reliable data can we expect? in Stuiver, M and Kra, RS, eds, Internatl 14C conf, 10th, Proc: Radiocarbon, v 22, no. 3, p 858–862.Google Scholar
Srdoč, D, Horvatinčić, N, Obelić, B and Sliepčević, A, 1982, Rudjer Boskovic Institute radiocarbon measurements VII: Radiocarbon, v 24, p 325–371.Google Scholar
Srdoč, D, Sliepčević, A, Obelić, B and Horvatinčić, N, 1979, Rudjer Boskovic Institute radiocarbon measurements V: Radiocarbon, v 21, p 131–137.Google Scholar
Tamers, M A and Scharpenseel, H W, 1970, Sequential sampling of radiocarbon in groundwater, in Symposium on isotope hydrology, Proc: IAEA, Vienna, p 241–257.Google Scholar
Vogel, J C, 19/0, Carbon-14 dating of groundwater, in Symposium on isotope hydrology, Proc: IAEA, Vienna, p 225–239.Google Scholar