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Use of 39Ar and 14C for Groundwater Dating

Published online by Cambridge University Press:  18 July 2016

Heinz Hugo Loosli  and
Hans Oeschger
Heinz Hugo Loosli
Affiliation:
Physics Institute, University of Bern Sidlerstrasse 5, CH-3012 Bern, Switzerland
Hans Oeschger
Affiliation:
Physics Institute, University of Bern Sidlerstrasse 5, CH-3012 Bern, Switzerland
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Abstract

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Cosmic-ray produced atmospheric 39Ar activity (T1/2 = 269 yr) has been determined at 0.11 ±0.012 dpm/lt argon. Ice samples from two profiles in Greenland bore holes showed conclusively that 39Ar dating leads to correct ages. Corrections can be made for possible contamination of the samples with ambient air during field extraction and during laboratory processing by measuring 85Kr in the same samples.

The following isotopes: 14C, 39Ar, 85Kr, 3H, partly 32Si, 13C, and 18O were investigated in 20 groundwater samples. Unexpectedly large discrepancies between “14C ages” and “39Ar ages” were observed for many of these samples. For example, a horizontal profile of a confined sandstone aquifer in the Franconian Albvorland showed decreasing 39Ar and 14C activities from respectively, 100 percent to 17 percent and 80 percent to 0.3 percent of modern activity, corresponding to elapsed time periods of 700 and >20,000 years, respectively.

It seems unlikely that gas exchange through the aquiclude is the cause of this discrepancy. It can neither be explained by only assuming that the water represents a mixing of components with different ages. We detected the possibility of underground production of 39Ar in thermal spring water from Zurzach, Switzerland. Its argon showed higher specific activity than atmospheric argon. Elsewhere, however, samples were found containing no detectable 39Ar activity: two wells of a confined carstic aquifer in Ingolstadt, Germany, show less than 7 percent atmospheric activity.

In our opinion, the assumptions on which the 14C method in hydrology are based need to be critically re-examined. It is possible that for some aquifers carbonate exchange between solid and liquid phases in the aquifer changes 14C results to a larger degree than generally assumed.

Type
Soils and Groundwater
Information
Radiocarbon , Volume 22 , Issue 3: Heidelberg , 1980 , pp. 863 - 870
Copyright
Copyright © The American Journal of Science

References

Andres, G and Geyh, M A, 1970, Untersuchungen über den Grundwasserhaushalt im überdeckten Sandsteinkeuper mit Hilfe von 14C- und 3H-Wasseranalysen: Wasserwirtschaft, v 60, p 259–263.Google Scholar
Apel, R, 1971, Hydrologische Untersuchungen im Malmkarst der südlichen und mittleren Frankenalb: Doctoral dissert, Ludwig-Maximilian-Univ, Munich, West Germany.Google Scholar
Ciccioli, P, Cooper, W T, Hammer, P M, and Hayes, J M, 1978, Organic solute mineral surface interactions: a new method for the determination of ground water velocities: Water Resources Research 1978.Google Scholar
Geyh, M A, 1972, Basic studies in hydrology and 14C and 3H measurements: Internatl geol cong, 24th, Montreal, 1972, Proc, p 227–234.Google Scholar
Geyh, M A 1974, Erfahrungen mit der 14C- und 3H-Methode in der angewandten Hydrologie: Oesterr Wasserwirtschaft, v 26, p 49–54.Google Scholar
Loosli, H H, Heimann, Martin, and Oeschger, Hans, 1980, Low-level gas proportional counting in an underground laboratory, in Stuiver, Minze and Kra, Renee, eds, Internatl radiocarbon conf, 10th, Proc: Radiocarbon, v 22, no. 2, p 461–469.Google Scholar
Loosli, H H and Oeschger, Hans, 1978, Ar-39, C-14 and Kr-85 measurements in groundwater samples: Isotope Hydrology v 2, IAEA Vienna, 1979, p 931–947.Google Scholar
Münnich, K O, 1968, Isotopen-Datierung von Grundwasser: Die Naturwissenschaf en, v 55, no. 4, p 158–163.Google Scholar
Oeschger, Hans, Gugelmann, A, Loosli, H H, Schotterer, U, Siegenthaler, U, and Wiest, W, 1974, Isotope techniques in groundwater hydrology, vol 2: IAEA, Vienna, p 179–190.Google Scholar
Oeschger, Hans and Loosli, H H, 1975, New developments in sampling and low level counting of natural radioactivity, in Internatl conf on low radioactivity measurements and applications, Proc: High Tatras, 6-10 Oct 1975, p 13–22.Google Scholar
Oeschger, Hans, Stauffer, B, Bucher, P, and Loosli, H H, 1977, Extraction of gases and dissolved and particulate matter from ice in deep boreholes, in Symposium on isotopes and impurities in snow and ice, Proc: Grenoble, Sept 1975, p 307–311.Google Scholar
Pearson, F J and Hanshaw, B B, 1970, Sources of dissolved carbonate species in groundwater and their effects on carbon-14 dating: Isotope Hydrology, IAEA, Vienna, p 271–286.Google Scholar
Przewlocki, K, 1975, Hydrologie interpretation of the environmental isotope data in the eastern Styrian basin: Steirische Beitr Hydrolgeolog, v 27, p 85–133.Google Scholar
Thilo, L and Münnich, K O, 1970, Reliability of C-14 dating of groundwater: Effect of carbonate exchange: Isotope Hydrology, IAEA Vienna, p 259–270.Google Scholar
Wendt, I, Stahl, W, Geyh, M A, and Fauth, F, 1967, Model experiments for C-14 water age determination: Isotopes in Hydrology, IAEA, Vienna, p 321–337.Google Scholar