scholarly journals Expectations of scatter in equivalent-dose distributions when using multi-grain aliquots for OSL dating

2011 ◽  
Vol 38 (4) ◽  
pp. 424-431 ◽  
Author(s):  
Alastair Cunningham ◽  
Jakob Wallinga ◽  
Philip Minderhoud
Keyword(s):  
Dose Rate ◽  
Equivalent Dose ◽  
Osl Dating ◽  
Dose Distributions ◽  
Sensitivity Distribution ◽  
Minimum Age ◽  
Single Grain ◽  
Counting Statistics ◽  
Partial Bleaching

AbstractIn the OSL dating of sediment, the scatter in equivalent dose (D e) between grains is almost always larger than would be expected due to counting statistics alone. Some scatter may be caused by insufficient (partial) bleaching of some of the grains prior to deposition. In order to date partially bleached sediment, it is essential to estimate the amount of scatter caused by other processes (e.g. grain-to-grain variability in the natural dose rate). Measurements of such scatter are performed at the single-grain level; by contrast, most OSL dating is performed on multi-grain subsamples, for which grain-to-grain scatter is reduced through averaging.Here we provide a model for estimating the expected scatter (i.e. excluding that caused by partial bleaching) for multi-grain aliquots. The model requires as input the single-grain sensitivity distribution, the number of grains in the sub-samples, and the expected scatter at the single-grain level, all of which can be estimated to an adequate degree. The model compares well with measured values of scatter in D e, determined using aliquots of various sizes, and can be used to help produce a minimum-age D e from multi-grain subsamples that is consistent with single-grain data.

scholarly journals Methodological study on single grain OSL dating of mortars: Comparison of five reference archaeological sites

2017 ◽  
Vol 44 (1) ◽  
pp. 77-97 ◽  
Author(s):  
Petra Urbanová ◽  
Pierre Guibert
Keyword(s):  
Input Parameter ◽  
Osl Dating ◽  
Archaeological Sites ◽  
Annual Dose ◽  
Dose Distributions ◽  
Minimum Age ◽  
Age Model ◽  
Single Grain ◽  
External Consistency ◽  
The Impact

Abstract The paper focuses on single grain OSL dating of quartz extracted from known age archaeological mortars, potentially representing a new tool for dating the construction of historical buildings. Apart from SG-OSL measurements and annual dose rate determination, the samples are systematically studied by means of optical microscopy, EDX-SEM cartography and beta autoradiography in order to evaluate the possible microdosimetric heterogeneity of each sample, arising principally from local variations of potassium content. Besides the practical aspects concerning sampling, preparation and appropriate choice of measurement conditions, the paper aims at the differences in microstructure and in elementary composition between different mortars and attempts to evaluate the impact of these aspects on the dispersion of equivalent dose distributions. Finally, archaeological doses (paleodoses) are calculated by using central age model (CAM), minimum age model (MAM) and internal-external consistency criterion (IEU). The appropriateness of these models for the exploitation of the measured SG-OSL data as well as for a hypothesis on the estimation of the input parameter needed to run these models are discussed. Three categories of mortars were identified: samples without any exploitable SG-OSL signal, samples that could have been reliably dated and poorly bleached samples affected by microdosimetric variations whose dating still remains complicated. Finally, the hypothesis on distinguishing between reliable and questionable dating results is raised and the potentials of the method for dating mortars are pointed out.

scholarly journals Quartz Single Grain Osl Sensitivity Distributions: Implications for Multiple Grain Single Aliquot Dating

2007 ◽  
Vol 26 (-1) ◽  
pp. 19-29 ◽  
Author(s):  
Edward Rhodes
Keyword(s):  
Numerical Model ◽  
National Park ◽  
Australian Capital Territory ◽  
Sensitivity Distribution ◽  
Minimum Age ◽  
Age Model ◽  
Single Grain ◽  
Simpson Desert ◽  
Simple Numerical Model ◽  
Real Multiple

Quartz Single Grain Osl Sensitivity Distributions: Implications for Multiple Grain Single Aliquot DatingA simple probabilistic numerical model was used to construct synthetic Dedistributions by combining the simulated OSL from grains of different sensitivities and with various simulated Devalues. This is useful for exploring the complex patterns generated by summing the signals from many grains in real, multiple grain OSL dating scenarios, and demonstrates that the form of the sensitivity distribution has a significant effect on the identification of mixed dose populations in multiple grain single aliquot methods. I describe the simple numerical model and its implementation. I present measured quartz single grain OSL sensitivity distributions for an aeolian dune sample from the Simpson Desert, Northern Territory, Australia, and from a suite of 9 fluvial sediments from Namadgi National Park, Australian Capital Territory, Australia, to illustrate effects that result from natural differences. Minimum age model determinations of synthetic Devalues are used to assess the validity of dose values estimated from multiple grain single aliquot measurements.

scholarly journals Application of different protocols and age-models in OSL dating of earthen mortars

2017 ◽  
Vol 44 (1) ◽  
pp. 341-351 ◽  
Author(s):  
Laura Panzeri ◽  
Michela Cantù ◽  
Marco Martini ◽  
Emanuela Sibilia
Keyword(s):  
Statistical Methods ◽  
Northern Italy ◽  
Equivalent Dose ◽  
Osl Dating ◽  
Accurate Evaluation ◽  
Single Grain

Abstract In this study, OSL dating was applied to earthen mortars, consisting in a quartz-rich aggregate dispersed in silty-clayey matrix. The samples were taken from two independently dated structures in Cremona, Northern Italy (Palazzo Raimondi, 1495–1499 AD and Palazzo Soldi, 1770–1790 AD). The evaluation of the equivalent dose (De) was attempted with both the multigrain and the single grain protocols using the 150–250 μm quartz fraction. The reliability and effectiveness of the various statistical methods in identifying the well-bleached samples were tested. The use of the multi-grain technique gave unreliable results, due to the high amount of poorly bleached grains. With the single-grain technique, more promising results were obtained: in particular, the un-log MAM3 and IEU models allowed an accurate evaluation of the mortar expected age in most cases, even if the precision is still relatively low.

scholarly journals Modelling dose rate to single grains of quartz in well-sorted sand samples: The dispersion arising from the presence of potassium feldspars and implications for single grain OSL dating

2015 ◽  
Vol 27 ◽  
pp. 52-65 ◽  
Author(s):  
Guillaume Guérin ◽  
Mayank Jain ◽  
Kristina J. Thomsen ◽  
Andrew S. Murray ◽  
Norbert Mercier
Keyword(s):  
Dose Rate ◽  
Osl Dating ◽  
Single Grain

scholarly journals Optically stimulated luminescence and isothermal thermoluminescence dating of high sensitivity and well bleached quartz from Brazilian sediments: from Late Holocene to beyond the Quaternary?

2016 ◽  
Vol 46 (suppl 1) ◽  
pp. 209-226 ◽  
Author(s):  
André Oliveira Sawakuchi ◽  
Vinicius Ribau Mendes ◽  
Fabiano do Nascimento Pupim ◽  
Thays Desiree Mineli ◽  
Ligia Maria Almeida Leite Ribeiro ◽  
...  
Keyword(s):  
Late Holocene ◽  
High Sensitivity ◽  
Equivalent Dose ◽  
Optically Stimulated Luminescence ◽  
Osl Dating ◽  
Fluvial Sediments ◽  
Dose Distributions ◽  
Age Limit ◽  
Sediment Mixture

ABSTRACT: The development of optically stimulated luminescence (OSL) dating of sediments has led to considerable advance in the geochronology of the Quaternary. OSL dating is a well established technique to determine sediment burial ages from tens of years to few hundred thousand years. Recent studies have shown that Quaternary sediments of Brazil are dominated by quartz grains with high luminescence sensitivity, allowing the determination of precise and reliable OSL burial ages. In this paper, we show examples of OSL dating of quartz aliquots and single grains from different regions in Brazil, including young coastal-eolian Late Holocene (< 100 years) to Late Pleistocene (~ 150 ka) fluvial sediments. We discuss the OSL data and ages of sediments from carbonate and terrigenous (distributary and tributary systems) fluvial depositional contexts in Brazil. Most of the studied fluvial sediments show equivalent dose distributions with low to moderate dispersion, suggesting well bleached sediments. The comparison between aliquot and single grain data suggests that high overdispersion in equivalent dose distributions of some samples is more related with sediment mixture due to bioturbation than with incomplete bleaching during transport. Well bleached fluvial sediments contrast with the poor bleached pattern usually described for fluvial sediments in the literature. A large part of the fluvial sedimentary record in Brazil is older than the age limit for quartz OSL dating using blue light stimulation. Thus, isothermal thermoluminescence (ITL) dating protocols were tested for dating of fluvial sands from the Xingu River (eastern Amazonia). The studied sample can recover reliable equivalent doses up to 1600 Gy using the ITL 310oC signal. Therefore, this signal would be suitable to extend the age limit of quartz luminescence to the whole Quaternary or beyond (> 2 Ma) in the low dose rate (0.5 - 1.0 Gy/ka) environments typical for Brazilian sediments.

scholarly journals Towards an improvement of optically stimulated luminescence (OSL) age uncertainties: modelling OSL ages with systematic errors, stratigraphic constraints and radiocarbon ages using the R package BayLum

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 229-245
Author(s):  
Guillaume Guérin ◽  
Christelle Lahaye ◽  
Maryam Heydari ◽  
Martin Autzen ◽  
Jan-Pieter Buylaert ◽  
...  
Keyword(s):  
R Package ◽  
Systematic Errors ◽  
Covariance Matrices ◽  
Optically Stimulated Luminescence ◽  
Osl Dating ◽  
Dose Rates ◽  
Determination Procedure ◽  
Single Grain ◽  
Measurement Uncertainties ◽  
Osl Age

Abstract. Statistical analysis has become increasingly important in optically stimulated luminescence (OSL) dating since it has become possible to measure signals at the single-grain scale. The accuracy of large chronological datasets can benefit from the inclusion, in chronological modelling, of stratigraphic constraints and shared systematic errors. Recently, a number of Bayesian models have been developed for OSL age calculation; the R package “BayLum” presented herein allows different models of this type to be implemented, particularly for samples in stratigraphic order which share systematic errors. We first show how to introduce stratigraphic constraints in BayLum; then, we focus on the construction, based on measurement uncertainties, of dose covariance matrices to account for systematic errors specific to OSL dating. The nature (systematic versus random) of errors affecting OSL ages is discussed, based – as an example – on the dose rate determination procedure at the IRAMAT-CRP2A laboratory (Bordeaux). The effects of the stratigraphic constraints and dose covariance matrices are illustrated on example datasets. In particular, the benefit of combining the modelling of systematic errors with independent ages, unaffected by these errors, is demonstrated. Finally, we discuss other common ways of estimating dose rates and how they may be taken into account in the covariance matrix by other potential users and laboratories. Test datasets are provided as a Supplement to the reader, together with an R markdown tutorial allowing the reproduction of all calculations and figures presented in this study.

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