Distribution in SAR palaeodoses due to spatial heterogeniety of natural beta dose
More details
Hide details
Physical Research Laboratory, Navrangpura, Ahmedabad, 380 009, India
Online publication date: 2011-06-19
Publication date: 2011-09-01
Geochronometria 2011;38(3):190-198
In luminescence dating of sediments, Mayya et al. (2006) pointed out that at single grain level, the beta dose for quartz grains is heterogeneous. This heterogeneity arises due the fact that the total potassium in sediment is contributed by few feldspar grains with up to 11–14% stoichiometric potassium (Huntley and Baril, 1997). Beta particles have a range of ∼2 mm, which is comparable to grain sizes and inter-grain distances. This fact implies that the spatial fluctuation of beta emitters (K-feldspars) around individual quartz grains results in heterogeneous dose deposition. These fluctuations therefore, lead to an inherent spread in palaeodoses received by individual quartz grains. In this study, we compute the spread in single aliquot palaeodoses that arises exclusively due to heterogeneity in beta radiation dose received by individual grains. We thus postulate that ‘single aliquots’ (comprising several — typically 100 — heterogeneously irradiated single grains) would have an inherent spread in the palaeodose. In this work, we used Monte Carlo simulations to quantify the extent of spread in palaeodoses arising due to heterogeneity of beta dose and hence put a limit on the precision of age estimation. Simulations results indicated, that, 1) the average of the single aliquot palaeodoses provides the closest approximation to the true palaeodose, 2) the minimum number of aliquots that are needed to obtain a robust estimate of average palaeodose value depend upon desired precision and the concentration of K, and 3) the ratio of maximum to minimum single aliquot palaeodose values for a given K concentration provides a measure of inherent spread arising due to beta dose heterogeneity. Any spread over and above this range, can be ascribed to other sources such as heterogeneous bleaching and sensitivity changes. Radiation dose from other uniformly distributed sources of beta particles (U, Th and Rb) however would reduce this spread.
Arnold LJ and Roberts RG, 2009. Stochastic modelling of multi-grain equivalent dose (D e) distributions: Implications for OSL dating of sediment mixtures Quaternary Geochronology 4(3): 204–230, DOI 10.1016/j.quageo.2008.12.001.
Bailey R, 2002. Simulations of variability in the luminescence characteristics of natural quartz and its implications for estimates of absorbed dose Radiation Protection Dosimetry 100(1–4): 33–38.
Bevington PR and Robinson DK, 2003. Data reduction and error analysis for the physical sciences. Mcgraw-Hill, New York, 3rd: 336 pp.
Duller GAT, Bøtter-Jensen L and Murray AS, 2000. Optical dating of single sand-sized grains of quartz: Sources of variability Radiation Measurements 32(5–6): 453–457, DOI 10.1016/S1350-4487(00)00055-X.
Galbraith RF, 1988. Graphical display of estimates having differing standard errors Technometrics 30(3): 271–281.
Galbraith RF, 1990. Radial plots: Graphical assessment of spread in ages Nuclear Tracks and Radiation Measurements 17(3): 207–214, DOI 10.1016/1359-0189(90)90036-W.
Huntley DJ and Baril MR, 1997. The K content of K-feldspars being measured in optical dating or in thermoluminescence dating. Ancient TL 15(1): 11.
Juyal N, Chamyal LS, Bhandari S, Bhushan R and Singhvi AK, 2006. Continental record of the southwest monsoon during the last 130 ka: Evidence from the southern margin of the Thar desert, India Quaternary Science Reviews 25(19–20): 2632–2650, DOI 10.1016/j.quascirev.2005.07.020.
Mayya YS, Morthekai P, Murari MK and Singhvi AK, 2006. Towards quantifying beta microdosimetric effects in single-grain quartz dose distribution Radiation Measurements 41(7–8): 1032–1039, DOI 10.1016/j.radmeas.2006.08.004.
McFee CJ and Tite MS, 1998. Luminescence dating of sediments-the detection of high equivalent dose grains using an imaging photon detector Archaeometry 40(1): 153–168, DOI 10.1111/j.1475-4754.1998.tb00830.x.
Morthekai P, 2007. Investigations on radiation dose distribution in natural environment and their implications in luminescence chronology. Unpublished Thesis, Gujarat University.
Murray AS and Roberts RG, 1997. Determining the burial time of single grains of quartz using optically stimulated luminescence Earth and Planetary Science Letters 152(1–4): 163–180, DOI 10.1016/S0012-821X(97)00150-7.
Murray AS and Wintle AG, 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol Radiation Measurements 32(1): 57–73, DOI 10.1016/S1350-4487(99)00253-X.
Roberts R, Bird M, Olley J, Galbraith R, Lawson E, Laslett G, Yoshida H, Jones R, Fullagar R, Jacobsen G and Hua Q, 1998. Optical and radiocarbon dating at jinmium rock shelter in northern Australia. Nature 393(6683): 358–362, DOI 10.1038/30718.
Singhvi AK, Stokes S, Chauhan N, Nagar YC and Jaiswal M, 2011. Changes in natural OSL sensitivity during single aliquot regeneration procedure and their implications for equivalent dose determination Geochronometria 38(3): 231–241, DOI 10.2478/s13386-011-0028-3.
Journals System - logo
Scroll to top