NATURAL THERMOLUMINESCENCE AND TERRESTRIAL AGES OF METEORITES FROM A VARIETY OF TEMPERATURE REGIMES

The natural thermoluminescence of meteorites from Antarctica, the Prai rie and western States of the US and the Sahara Desert has been determ ined and compared with estimates of terrestrial age (time since fall) obtained by isotropic measurements. After fall on Earth, the natural T L of meteorites decays from the high values caused by high cosmic ray dose rates and low temperatures of space. The decay is temperature dep endent, but can theoretically modelled. The present data show good agr eement between theory and observation. It is therefore possible to det ermine terrestrial ages from the natural TL data and theoretical TL de cay curves, selecting appropriate temperatures from meteorological dat a. About 20% of the meteorites have low natural TL values which result in unrealistically long terrestrial age estimates. These meteorites a re readily distinguished from the others and usually have cosmic ray p roduced isotope activities which suggest atypical radiation histories in space. The low TL signal, and perhaps the unusual isotopic data, is readily understood in terms of passing close to the Sun.