U/Th dating of impure carbonates: 230Th/232Th activity ratios in detrital material
In environmental age dating the 230Th/232Th activity ratio is widely used as an indicator of detrital contamination. A clear relationship between this activity ratio and the carbonate sample’s age has previously been demonstrated, whereby a detrital correction must be applied when the 230Th/232Th activity ratio of the leach drops to 20. We demonstrate that in some cases carbonate samples with 230Th/232Th well above 20 must be corrected, otherwise an overestimation of the sample’s age is obtained. Evaluation of the relationship between 230Th/234U and 230Th/232Th in the carbonate’s aliquots will enable evaluation of the limit at which a carbonate can be considered pure or impure.
KeywordsU/Th dating Carbonates Detrital material Age corrections Radio chronometry
This work was supported by the PaleoMed Project of Interreg IIIB of the EU MEDOC Programme: 2002-02-4.1-U-048, by the Government of Gibraltar and by Huelva University.
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