Optically Stimulated Luminescence Analysis Research Articles

The use of OSL dating in unstructured sands: the archaeology and chronology of the Hutton Sands at Canteen Kopje (Northern Cape Province, South Africa)

Archaeological research at the site of Canteen Kopje, Northern Cape Province, South Africa, has focused on the rich Earlier Stone Age assemblages recovered from the Younger Vaal Gravels. This paper presents the results of excavation and optically stimulated luminescence (OSL) dating of the overlying Hutton Sands. We discuss the evidence for colonial period interaction between diamond miners and indigenous groups at the site, as well as the presence of an earlier phase of terminal Middle Stone Age/early Later Stone Age occupation. The OSL analyses demonstrate the potential distortion of OSL ages due to substantial bioturbation and its effect on the dating of archaeological sites situated in unconsolidated sands.

Improving the accuracy and precision of equivalent doses determined using the optically stimulated luminescence signal from single grains of quartz

Optically stimulated luminescence (OSL) measurements of quartz are widely used to measure equivalent dose ( D e ). At radiation doses above ∼100 Gy, saturation of traps results in a decrease in the rate of growth of the OSL signal, and this makes calculation of D e increasingly difficult. A series of dose recovery experiments was undertaken using single grains of quartz from Kalambo Falls, Zambia to explore saturation of single grains. When the OSL signal from many grains is averaged, the characteristic dose ( D 0 ) is 47 Gy, typical of published values for quartz. However, D 0 for individual grains varies from ∼10 to 100 Gy. Doses up to two times the average D 0 could be accurately recovered, but above this dose the D e became increasingly underestimated. Overdispersion for this type of experiment should be zero, but was observed in all data sets; furthermore the value of overdispersion increased with D e . An additional acceptance criterion, the Fast Ratio, is suggested for single grain OSL analysis. This criterion assesses the relative contribution of the fast component of the OSL signal. Including this as an additional acceptance criterion leads to an improved precision, with overdispersion reduced to zero, and improved accuracy in dose recovery at high doses. ► Dose recovery measurements using OSL from single grains of quartz are expected to have zero overdispersion. ► This paper shows that overdispersion in dose recovery data increases systematically with the size of the dose being recovered. ► The Fast Ratio is shown to reduce overdispersion to near zero, and this is recommended as an additional acceptance criteria. ► Single grain OSL measurements may be a more accurate method for dating old sediments than multiple grain measurements.

Optically stimulated luminescence dating of young (

The reliability of single-grain optically stimulated luminescence (OSL) dating of young (<500 years old) samples is assessed by examining the results of 166 single-grain OSL analyses of Australian alluvial, lacustrine, estuarine, coastal and marine sediment samples. All samples have been analysed using the modified SAR protocol of Olley et al. [2004b. Optical dating of Holocene sediments from a variety of geomorphic settings using single grains of quartz. Geomorphology 60, 337–358], with burial doses ( D b) calculated by fitting a single Gaussian curve to the peak of a multi-Gaussian summed probability distribution (PDF Gaussian). The near-equivalence of this approach to currently accepted methods of palaeodose estimation – namely the minimum age and central age models of Galbraith et al. [1999. Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: part I, experimental design and statistical models. Archaeometry 41, 339–364] – is demonstrated. Considered as a whole, OSL ages calculated using the PDF Gaussian D b determination method are consistent with other chronometric, geomorphological, botanical and historical indicators of depositional age, while four alternative (previously published) methods are generally less reliable when applied to the samples analysed here. The single-grain data from 12 samples of known age (reported by Olley et al. [2004b. Optical dating of Holocene sediments from a variety of geomorphic settings using single grains of quartz. Geomorphology 60, 337–358]) are re-analysed using the PDF Gaussian approach, with all but one yielding a D b consistent with the independently known age. Examples of luminescence data (dose recovery tests, preheat plateaux, continuous-wave and linear-modulated OSL, growth curves, single-grain dose distributions) are provided that together indicate the suitability of Australian quartz for dating young sediments.

Aeolian sand movement and relative sea-level rise in Ho Bugt, western Denmark, during the `Little Ice Age'

This study documents an extensive aeolian sand sheet buried in the salt marshes of the Ho Bugt embayment in western Denmark. The extent of the sand sheet was mapped from c. 60 cores and sections, which were also used to reconstruct late-Holocene changes in relative sea level based on diatom analyses. Chronology was provided by optically stimulated luminescence (OSL) and radiocarbon dating. Our study shows that since 2000 cal. yr BP relative sea level in Ho Bugt has risen by approximately 1.5 m. The overall rise was punctuated by two periods with higher than average rates of sea-level rise, the first between 2000 and 1400 cal. yr BP and the second commencing c. 500 cal. yr BP. Around 700 cal. yr BP the evolution of the Skallingen Spit may have been responsible for a reduction in the local tidal range and the formation of an extensive `black layer' in the western part of the embayment. OSL analyses date the sand sheet to between AD 1460 ± 40 and AD 1550 ± 30 (490 ± 40 and 400 ± 30 cal. yr BP), consistent with a period of increased storminess, coastal dune building, saltmarsh formation and increased relative sea-level rise during the early part of the LIA. Other studies have ascribed formation of coastal dunes along western European coastlines during the `Little Ice Age' (LIA) to a combination of increased storminess and low relative sea level. In contrast, we conclude that during the LIA in western Denmark, storminess, transgressive conditions and relative sea-level rise, rather than a sea-level low stand, were important contributing factors to coastal sand movement and dune formation.

Optically stimulated luminescence dating of single and multiple grains of quartz from perennially frozen loess in western Yukon Territory, Canada: Comparison with radiocarbon chronologies for the late Pleistocene Dawson tephra

Optically stimulated luminescence (OSL) dating of perennially frozen loess was tested on quartz grains extracted from deposits associated with the late Pleistocene Dawson tephra in western Yukon Territory, Canada. OSL samples were obtained from ice-rich loess bracketing the Dawson tephra, while radiocarbon ( 14C) samples were collected from the bulk sediments directly underlying the tephra and from a ground-squirrel burrow 2.7 m below the tephra. Here we report the OSL characteristics and ages of the extracted quartz grains, as well as additional radiocarbon ages for samples described in Froese [2002. Age and significance of the late Pleistocene Dawson tephra in eastern Beringia. Quaternary Science Reviews 21, 2137–2142; 2006. Seasonality of the late Pleistocene Dawson tephra and exceptional preservation of a buried riparian surface in central Yukon Territory, Canada. Quaternary Science Reviews 25, 1542–1551]. We refine the time of Dawson tephra deposition to between 25,420±70 and 25,290±80 14C a BP. Bayesian analysis of constraining radiocarbon ages places the deposition of the Dawson tephra at between 30,433 and 30,032 cal a BP. Linear modulation (LM) OSL analysis of multi-grain aliquots of quartz showed that the initial part of the decay curve is dominated by a rapidly bleached (‘fast’) component; these samples, however, had relatively dim continuous wave (CW) OSL signals at the multi-grain aliquot (each composed of ∼80 grains) and single-grain scales of analysis. The single-aliquot regenerative-dose protocol was applied to multi-grain aliquots and single grains to obtain equivalent dose ( D e) values for samples collected from below and above the Dawson tephra. The D e values were examined graphically and numerically, the latter using the central age, minimum age, and finite mixture models. For multi-grain aliquots, the central age model gave weighted mean D e values between 30 and 50 Gy, which greatly underestimated the expected D e of ∼74–81 Gy for both samples studied. Possible reasons for these underestimations are discussed, and a solution proposed based on single-grain analysis. Measurements of single grains produced D e values in agreement with the expected D e, and yielded OSL ages of 28±5 and 30±4 ka for the samples taken from above and below the Dawson tephra, respectively. Examination of individual grains with differing luminescence behaviors showed that a significant number of the measured quartz grains exhibited anomalous luminescence properties that would have compromised the results obtained from multi-grain aliquots. We therefore recommend analysis of individual grains to overcome the age-shortfall from multi-grain analysis of these and similar samples of quartz.

Optical bleaching, TSL and OSL features of CVD diamond

Luminescence and optical features of chemical vapour deposition (CVD) diamond have been studied in view of the potential application of this material in ionising radiation dosimetry field. For this purpose, thermally stimulated luminescence (TSL) and optically stimulated luminescence (OSL) techniques have been used. A large amount of work has emphasised the excellent dosimetric properties of CVD diamond. Nevertheless, TSL measurements showed that after irradiation, this material is extremely sensitive to ambient light and the stored dose information is drastically affected by optical bleaching. From OSL analysis, it follows that both types of processes (TSL and OSL) were characterised by the same excitation and emission spectra and that optical bleaching originated from a broad stimulation band lying from visible to near infrared with a continuous character.

Application of the Sunna dosimeter film in gamma and electron beam radiation processing

Abstract The OSL (optically stimulated luminescence) based Sunna film containing a microcrystalline dispersion of LiF in a polymer matrix has been recently introduced for high-dose dosimetry. Our previous investigations revealed the applicability of the system in the dose range of 0.01–100 kGy, but irradiation temperature and dose rate effects above 5 kGy reduced its usefulness. The recent discovery of the use of spectrophotometric analysis in the UV range for measuring doses above 5 kGy is a suitable option, while the OSL analysis can be applied for measuring lower doses due to the lack of temperature effect on the response of the film below 1 kGy. The film can be applied both in gamma and electron fields, although its response to the two types of radiation is somewhat different. No significant effects of UV light and humidity have been found, and effects of irradiation temperature are only significant in the case of OSL analysis for doses above 5 kGy. The applicability of two types of Sunna films in electron and gamma radiation processing is discussed in the paper.