The dose dependency of the over-dispersion of quartz OSL single grain dose distributions

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    Abstract

    The use of single grain quartz OSL dating has become widespread over the past decade, particularly with application to samples likely to have been incompletely bleached before burial. By reducing the aliquot size to a single grain the probability of identifying the grain population most likely to have been well-bleached at deposition is maximised and thus the accuracy with which the equivalent dose can be determined is – at least in principle – improved.

    However, analysis of single grain dose distributions requires knowledge of the dispersion of the well-bleached part of the dose distribution. This can be estimated by measurement of a suitable analogue, e.g. a well-bleached aeolian sample, but this requires such an analogue to be available, and in addition the assumptions that the sample is in fact a) well-bleached, and b) has a similar dose rate heterogeneity to the fossil deposit. Finally, it is an implicit assumption in such analysis that any over-dispersion is not significantly dose dependent.

    In this study we have undertaken laboratory investigations of the dose dependency of over-dispersion using a well-bleached modern sample with an average measured dose of 36 ± 3 mGy. This sample was prepared as heated (750 °C for 1 h), bleached and untreated portions which were then given uniform gamma doses ranging from 100 mGy to 208 Gy. We show that for these samples the relative laboratory over-dispersion is not constant as a function of dose and that the over-dispersion is smaller in heated samples. We also show that the dim grains in the distributions have a greater over-dispersion than the bright grains, implying that insensitive samples will have greater values of over-dispersion than sensitive samples.

    Original languageEnglish
    JournalRadiation Measurements
    Volume47
    Pages (from-to)732-739
    ISSN1350-4487
    DOIs
    Publication statusPublished - 2012
    Event13th International Conference on Luminescence and Electron Spin Resonance Dating - LED 2011 - Torun, Poland
    Duration: 10 Jul 201114 Jul 2011

    Conference

    Conference13th International Conference on Luminescence and Electron Spin Resonance Dating - LED 2011
    CountryPoland
    CityTorun
    Period10/07/201114/07/2011

    Keywords

    • OSL
    • Single grain
    • Quartz
    • Over-dispersion

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