Luminescence isochron dating: a new approach using different grain sizes.
A new approach to isochron dating is described using different sizes of quartz and K-feldspar grains. The technique can be applied to sites with time-dependent external dose rates. It is assumed that any underestimation of the equivalent dose (De) using K-feldspar is by a factor F, which is independent of grain size (90-350 microm) for a given sample. Calibration of the beta source for different grain sizes is discussed, and then the sample ages are calculated using the differences between quartz and K-feldspar De from grains of similar size. Two aeolian sediment samples from north-eastern China are used to illustrate the application of the new method. It is confirmed that the observed values of De derived using K-feldspar underestimate the expected doses (based on the quartz De) but, nevertheless, these K-feldspar De values correlate linearly with the calculated internal dose rate contribution, supporting the assumption that the underestimation factor F is independent of grain size. The isochron ages are also compared with the results obtained using quartz De and the measured external dose rates.
Zhao
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Department of Earth Sciences, The University of Hong Kong, Hong Kong.
Li
S H
SH
D000512:Alpha Particles; D000538:Aluminum Silicates / Q000737:chemistry*; D001610:Beta Particles; D002138:Calibration; D017680:Potassium Compounds / Q000737:chemistry*; D011791:Quartz / Q000737:chemistry*; D011868:Radioisotopes / Q000032:analysis; D015203:Reproducibility of Results; D013819:Thermoluminescent Dosimetry / Q000379:methods
D000538:Aluminum Silicates; D017680:Potassium Compounds; D011868:Radioisotopes; C016447:feldspar; D011791:Quartz