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DETERMINATION OF CARBON-14 BY ACCELERATOR MASS-SPECTROMETRY: OCEANOGRAPHIC APPLICATIONS. J. C. Duplessy, E. Bard, M. Arnold and P. Maurice Centre des Faibles Radioactivites Laboratoire mixte CNRS-CEA 91198 Gif-sur-Yvette Cedex FRANCE ABSTRACT Accelerator mass-spectrometry (AMS) enables the determination of 14C/12C ratios with only one mg of carbon, i.e. with samples 1000 times smaller than those required for conventional radiocarbon g-counting. For sediment dating, radiocarbon ages can thus be measured on monospecific samples of 1000-2000 foraminifera picked by hand. This enables an age to be assigned to the same sample which is to be used in the oxygen isotope measurement or to the dominant species which drive sea surface paleotemperature estimates. For studying the oceanic circulation within the main thermocline and the carbon cycle, 14C measurements can be obtained with water samples of only 100 ml, without major chemical treatment on board. INTRODUCTION Among cosmonuclides, 14 C with its half-life of 5,730 years has been widely-used for sediment dating and to explore the global ocean circulation in relation with the oceanic part of the carbon cycle. Until recent years, the 14C/12C ratio was only measured by the conventional g-counting method, which provides an accurracy up to 4 per mil but requires samples as large as 1-5g of carbon. This relatively large size of the samples was the cause of several difficulties in either sample collection or in interpretation of the geochemical significance of the analytical result. The development of AMS in recent years permits now to characterise 14C atoms by their mass and to count the 14C/ 1-7C ratio in samples as small as 1 mg of carbon with an accuracy of 1% for modern activities. The accuracy of this measurement should be improved in the near future. This dramatic reduction in the size of the samples required to make one analysis results in a burst of new applications. We shall describe in this paper some major advances in oceanography connected with the determination of 14 C in sediment and water samples using the Tandetron of Gif sur Yvette, a small tandem accelerator devoted to the measurement of cosmonuclides for geochemical studies in Earth's sciences. The routine procedure for AMS measurements has been described by Arnold et al. (1).
DOI link for DETERMINATION OF CARBON-14 BY ACCELERATOR MASS-SPECTROMETRY: OCEANOGRAPHIC APPLICATIONS. J. C. Duplessy, E. Bard, M. Arnold and P. Maurice Centre des Faibles Radioactivites Laboratoire mixte CNRS-CEA 91198 Gif-sur-Yvette Cedex FRANCE ABSTRACT Accelerator mass-spectrometry (AMS) enables the determination of 14C/12C ratios with only one mg of carbon, i.e. with samples 1000 times smaller than those required for conventional radiocarbon g-counting. For sediment dating, radiocarbon ages can thus be measured on monospecific samples of 1000-2000 foraminifera picked by hand. This enables an age to be assigned to the same sample which is to be used in the oxygen isotope measurement or to the dominant species which drive sea surface paleotemperature estimates. For studying the oceanic circulation within the main thermocline and the carbon cycle, 14C measurements can be obtained with water samples of only 100 ml, without major chemical treatment on board. INTRODUCTION Among cosmonuclides, 14 C with its half-life of 5,730 years has been widely-used for sediment dating and to explore the global ocean circulation in relation with the oceanic part of the carbon cycle. Until recent years, the 14C/12C ratio was only measured by the conventional g-counting method, which provides an accurracy up to 4 per mil but requires samples as large as 1-5g of carbon. This relatively large size of the samples was the cause of several difficulties in either sample collection or in interpretation of the geochemical significance of the analytical result. The development of AMS in recent years permits now to characterise 14C atoms by their mass and to count the 14C/ 1-7C ratio in samples as small as 1 mg of carbon with an accuracy of 1% for modern activities. The accuracy of this measurement should be improved in the near future. This dramatic reduction in the size of the samples required to make one analysis results in a burst of new applications. We shall describe in this paper some major advances in oceanography connected with the determination of 14 C in sediment and water samples using the Tandetron of Gif sur Yvette, a small tandem accelerator devoted to the measurement of cosmonuclides for geochemical studies in Earth's sciences. The routine procedure for AMS measurements has been described by Arnold et al. (1).
DETERMINATION OF CARBON-14 BY ACCELERATOR MASS-SPECTROMETRY: OCEANOGRAPHIC APPLICATIONS. J. C. Duplessy, E. Bard, M. Arnold and P. Maurice Centre des Faibles Radioactivites Laboratoire mixte CNRS-CEA 91198 Gif-sur-Yvette Cedex FRANCE ABSTRACT Accelerator mass-spectrometry (AMS) enables the determination of 14C/12C ratios with only one mg of carbon, i.e. with samples 1000 times smaller than those required for conventional radiocarbon g-counting. For sediment dating, radiocarbon ages can thus be measured on monospecific samples of 1000-2000 foraminifera picked by hand. This enables an age to be assigned to the same sample which is to be used in the oxygen isotope measurement or to the dominant species which drive sea surface paleotemperature estimates. For studying the oceanic circulation within the main thermocline and the carbon cycle, 14C measurements can be obtained with water samples of only 100 ml, without major chemical treatment on board. INTRODUCTION Among cosmonuclides, 14 C with its half-life of 5,730 years has been widely-used for sediment dating and to explore the global ocean circulation in relation with the oceanic part of the carbon cycle. Until recent years, the 14C/12C ratio was only measured by the conventional g-counting method, which provides an accurracy up to 4 per mil but requires samples as large as 1-5g of carbon. This relatively large size of the samples was the cause of several difficulties in either sample collection or in interpretation of the geochemical significance of the analytical result. The development of AMS in recent years permits now to characterise 14C atoms by their mass and to count the 14C/ 1-7C ratio in samples as small as 1 mg of carbon with an accuracy of 1% for modern activities. The accuracy of this measurement should be improved in the near future. This dramatic reduction in the size of the samples required to make one analysis results in a burst of new applications. We shall describe in this paper some major advances in oceanography connected with the determination of 14 C in sediment and water samples using the Tandetron of Gif sur Yvette, a small tandem accelerator devoted to the measurement of cosmonuclides for geochemical studies in Earth's sciences. The routine procedure for AMS measurements has been described by Arnold et al. (1).
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