Monday, 5 September 2005 - 4:00 PM

This presentation is part of: Terrestrial Sciences

Atmospheric 26Al and 10Be as a dating tool for climate archives

Matthias Auer1, Walter Kutschera1, Alfred Priller1, Dietmar Wagenbach2, Anton Wallner1, and Eva Maria Wild1. (1) Vienna Environmental Research Accelerator (VERA), Institut für Isotopenforschung und Kernphysik, Universität Wien, Währinger Str. 17, Wien, A-1090, Austria, (2) Institut für Umweltphysik, Rupprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 229, Heidelberg, D-69120, Germany

Atmospheric 26Al (t1/2 = 0.71 Ma) has several potential applications in atmospheric and climate research [1,2], but it has been only little investigated so far. In combination with 10Be (t1/2 = 1.52 Ma) absolute dating of climate archives may become possible: Due to the different half-lives, the decrease of the 26Al/10Be isotopic ratio with time can be used as a clock. Alternatively, 26Al could give complementary information for 10Be records, e.g. with respect to the aeolian dust component of 10Be or extraterrestrial signals. The extremely low abundance of both isotopes requires measurement by accelerator mass spectrometry (AMS).

In order to apply 26Al in climate research, the sources of 10Be and 26Al and their geochemical properties have to be well understood. In particular, the response of 26Al to the various different sources (terrestrial, atmospheric, resuspended atmospheric and extraterrestrial) may be different than that of 10Be, which could seriously limit the applicability of 26Al/10Be as a dating tool. On the other hand this differences might open up other applications. The long half-lives of 26Al and 10Be require a high precision measurement in order to reduce the uncertainty in dating. This is a challenge for the AMS measurement, primarily due to the combination of a very low abundance of atmospheric 26Al and the low ionization efficiency of Al in the AMS measurement. First measurements of atmospheric 26Al and 10Be have been carried out at the Vienna Environmental Research Accelerator (VERA) of the University of Vienna. We report here on the results and on the implications of sources and transport of 26Al and 10Be for using the 26Al/10Be isotopic ratio as a dating tool.

1 R. Middleton, J. Klein, 26Al: measurement and applications, Phil. Tans. R. Soc. Lond A 323, 121-143, 1987

2 G.M. Raisbeck, F. Yiou, J. Klein, R. Middleton, Accelerator mass spectrometry measurement of cosmogenic 26Al in terrestrial and extraterrestrial matter, Nature, 301, 690-692, 1983


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