Research article 07 May Correspondence : Galina Faershtein galaf gsi. Optically stimulated luminescence OSL of quartz is an established technique for dating late Pleistocene to late Holocene sediments. Recent developments in new extended-range luminescence techniques show great potential for dating older sediments of middle and even early Pleistocene age. Dose recovery and bleaching experiments under natural conditions indicated that the pIRIR signal is the most suitable for dating the Nilotic feldspar. Dating clastic sediments of Pleistocene age, particularly of middle and early Pleistocene, is an ongoing challenge. Several methods are available, but each has its limits. Magnetostratigraphy is binary reverse or normal polarity with several excursions and has low resolution extended periods with no reversals; Singer,
The principles of Luminescence Dating
Over the last 60 years, luminescence dating has developed into a robust chronometer for applications in earth sciences and archaeology. The technique is particularly useful for dating materials ranging in age from a few decades to around ,—, years. In this chapter, following a brief outline of the historical development of the dating method, basic principles behind the technique are discussed.
In solving geological and archaeological questions we apply Optically Stimulated Luminescence (OSL) dating to a wide range of depositional environments.
Luminescence dating is an absolute radiometric method of determining the age of a material since a key event in its history – typically burial in the case of sediments or firing in the case of ceramics or burnt stone. When a geological sediment is buried, the effects of the incoming solar radiation are removed. With this bleaching effect removed, the influence, albeit often weak, of naturally-occurring radioactive elements primarily potassium, uranium and thorium within the sediment together with incoming cosmic rays results in the accumulation of a signal within individual mineral grains most commonly quartz and feldspars.
It is this signal that is the key to luminescence dating techniques. Given an estimate of the rate of received ionizing radiation the dose rate, or D , and knowing the total accumulated dose the palaeodose; designated D E it is possible to derive an age since burial. This is obtained from the formula:. This accumulated signal results in luminescence i. Stimulation can be achieved by heating thermoluminescence or TL or exposure to light optically-stimulated luminescence or OSL.
Optical dating in a new light: A direct, non-destructive probe of trapped electrons
Luminescence dating depends on the ability of minerals to store energy in the form of trapped charge carriers when exposed to ionising radiation. Stimulation of the system, by heat in the case of thermoluminescence TL , or by light in the case of photo-stimulated luminescence PSL , or optically stimulated luminescence OSL. Following an initial zeroing event, for example heating of ceramics and burnt stones, or optical bleaching of certain classes of sediments, the system acquires an increasing luminescence signal in response to exposure to background sources of ionising radiation.
Luminescence dating is based on quantifying both the radiation dose received by a sample since its zeroing event, and the dose rate which it has experienced during the accumulation period.
Luminescence dating can be applied to the age range from present to approximately , years, thus spanning critical time-scales for human development.
Jain Mayank, Murray A. Optically stimulated luminescence dating: how significant is incomplete light exposure in fluvial environments? In: Quaternaire , vol. Fluvial Archives Group. Clermond-Ferrant Optically stimulated luminescence OSL dating of fluvial sediments is widely used in the interpretation of fluvial response to various allogenic forcing mechanisms during the last glacial-mterglacial cycle.
We provide here a non-specialist review highlighting some key aspects of recent development in the OSL dating technique relevant to the Quaternary fluvial community, and describe studies on dating of fluvial sediments with independent chronological control, and on recent fluvial sediment. Quaternaire, 15, , , p Obtaining chronologies for fluvial deposits is an important component in understanding the fluvial response to changes in climate, sea-level, tectonic and anthropogenic factors.
Optically stimulated luminescence OSL dating is now widely used by Quaternary scientists; it can provide ages in a range well beyond that of radiocarbon and on deposits from environments not conducive to the preservation of organic matter. This wide adoption of the technique is shown by many recent studies on aeolian, alluvial and marine stratigraphie records Murray and Olley,
Optically Stimulated Luminescence
Sedimentary deposits, such as aeolianites or loess, have been extensively dated using optically stimulated luminescence OSL signals from quartz Jacobs, ; Roberts, , the dating being almost invariably carried out using a grain size related to the dominant grain size present in the particular sedimentary unit. For aeolianites, sand-sized grains e. When only one grain size is used, the age estimates are usually found to be in chronological order down section, but there is often little or no independent age control, and thus it is not known if the selected grain size gives the correct age.
Still, samples below this showed age underestimation. In addition, for samples found below the last interglacial palaeosol, even the ages for the coarser grains were showing age underestimation compared with ages inferred from a model based on magnetic susceptibility changes Timar-Gabor and Wintle, It was also observed in these studies that the corrected luminescence signals for fine grains are higher than the ones measured on coarse grains and thus a possible explanation for the lower equivalent doses measured on fine grains could reside in the interpolation of these values on the different single aliquot regenerative SAR dose response curves encountered for the two grain sizes at doses higher than Gy.
ABSTRACT: Luminescence dating is a unique chronometric tool as it dates luminescence dating is in the range of years outlined above, an age range for.
Introduction How do we measure the OSL signal? How do we measure the radiation dose rate? Another way of dating glacial landforms is optically stimulated luminescence dating OSL. OSL is used on glacial landforms that contain sand, such as sandur or sediments in glacial streams. The OSL signal is reset by exposure to sunlight, so the signal is reset to zero while the sand is being transported such as in a glacial meltwater stream.
Once the sand grain has been buried and it is no longer exposed to sunlight, the OSL signal starts to accumulate. OSL works because all sediments have some natural radioactivity, caused by the presence of uranium, thorium and potassium isotopes in heavy minerals such as zircons. We analyse the quartz or feldspar minerals in sand deposits. When these quartz or feldspar minerals are exposed to the ionising radiation emitted by the radioactive isotopes in zircons, electrons within the crystals migrate and become trapped in their crystal structure.
The number of trapped electrons depends on the total amount of radiation that the mineral has been exposed to.
Luminescence Dating, Uncertainties, and Age Range
At the Netherlands Centre for Luminescence dating we develop new and improved luminescence dating methods, and we apply luminescence dating in collaboration with NCL partners and external users. We develop new and improved luminescence dating methods, and we apply luminescence dating in collaboration with NCL partners and external users. The Netherlands Centre for Luminescence dating is a collaboration of six universities and research centres in The Netherlands. Luminescence dating determines the last exposure to light or heat of natural minerals, mainly quartz and feldspar.
Thereby the method can be used to determine the time of deposition and burial of sediments, or the time of baking of ceramic artefacts pottery, brick.
Luminescence dating is based on the perception in solid state physics that saturation dose of quartz-OSL, however, limits the upper dating range to less than.
The impetus behind this study is to understand the sedimentological dynamics of very young fluvial systems in the Amazon River catchment and relate these to land use change and modern analogue studies of tidal rhythmites in the geologic record. Many of these features have an appearance of freshly deposited pristine sand, and these observations and information from anecdotal evidence and LandSat imagery suggest an apparent decadal stability.
Signals from medium-sized aliquots 5 mm diameter exhibit very high specific luminescence sensitivity, have excellent dose recovery and recycling, essentially independent of preheat, and show minimal heat transfer even at the highest preheats. Significant recuperation is observed for samples from two of the study sites and, in these instances, either the acceptance threshold was increased or growth curves were forced through the origin; recuperation is considered most likely to be a measurement artefact given the very small size of natural signals.
Despite the use of medium-sized aliquots to ensure the recovery of very dim natural OSL signals, these results demonstrate the potential of OSL for studying very young active fluvial processes in these settings. An important facet of the development of a geochronological technique is the investigation of potential age range. Much recent work in the luminescence field has focused on maximum achievable ages using high-temperature post-infrared infrared pIRIR signals from feldspars [ 1 , 2 ].
In contrast for quartz optically stimulated luminescence OSL , the more efficient signal resetting coupled with environments where grain reworking is evident make it well suited to assessment of minimum achievable age.
Optically stimulated Luminescence dating of quartz
Optically-Stimulated Luminescence is a late Quaternary dating technique used to date the last time quartz sediment was exposed to light. As sediment is transported by wind, water, or ice, it is exposed to sunlight and zeroed of any previous luminescence signal. Once this sediment is deposited and subsequently buried, it is removed from light and is exposed to low levels of natural radiation in the surrounding sediment.
Through geologic time, quartz minerals accumulate a luminescence signal as ionizing radiation excites electrons within parent nuclei in the crystal lattice.
The Vienna luminescence lab was founded in the year The lab was build with the perspective of elaborating key questions of environmental and Quaternary research, as e. Markus Fiebig markus. Optically stimulated luminescence OSL dating determines the last exposure to sunlight of a sediment. Sedimentation ages are calculated by deviding the equivalent dose De by the dose rate Do. Sources of natural radioactivity in sediments are Th, U, U and 40K found in a lot of minerals, and cosmic radiation.
Luminescence dating is applicable to a wide range of sediments. Most commonly, quartz or feldspar grains, ubiquitous in any sediment are used for De determination. Best suited are aeolian sediments such as dune sands or loess. Waterlain sediments such as fluvial, glaciofluvial or litoral deposits can be problematic with respect to OSL dating, due to partial resetting of the luminescence signal during transport and deposition.
However, recent methodological approaches, in particular, dating of individual grains of quartz, are able to deal with incomplete bleaching cf. Duller Furthermore, luminescence dating can be applied to fired materials such as ceramics or hearth stones.
In West Africa, preservation conditions of the sediments have only rarely been favorable to the recording of long sedimentary and archaeological sequences. Most of the artifacts are surface finds, making it difficult, if not impossible, to place them in chronological context, whether it be relative or absolute. However, in the Dogon Country, deep sedimentary deposits have been preserved in several sectors, trapping abundant evidence of human occupations during the Paleolithic and making it possible to study their chronology.
The age range of luminescence dating varies, at its lower end, with the sensitivity of the sample material and the efficiency of the zeroing process. At the upper.
In most cases, the uncertainty will be higher, due to random errors e. Dating is possible for a wide age range of a few decades to about half a million years, although uncertainties are usually relatively large toward the extremes of this range. As with any method, results of luminescence dating contain errors or uncertainties.
Adequate assessment of errors is important, for instance, to correctly assess rates of processes or leads and lags in natural or anthropogenic systems, or contemporaneity of different sites e. This of course only holds if all sources of uncertainty are adequately considered. Error propagation in luminescence dating is not straightforward. Uncertainties in both dose rate and palaeodose estimation should be taken into account, as both contribute equally to the uncertainty in the final age estimate.
Moreover, the errors should not only comprise the measurement uncertainties e. Finally, difficult-to-quantify errors may arise from assumptions made for equivalent dose or dose rate calculation.
All Research Projects
A Nature Research Journal.
OSL dating can be used to range sediments from decades up to, years in exceptional circumstances 1 although the thermoluminescence is more commonly.
Luminescence dating refers to a group of methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating. It is useful to geologists and archaeologists who want to know when such an event occurred. It uses various methods to stimulate and measure luminescence. All sediments and soils contain trace amounts of radioactive isotopes of elements such as potassium , uranium , thorium , and rubidium. These slowly decay over time and the ionizing radiation they produce is absorbed by mineral grains in the sediments such as quartz and potassium feldspar.
The radiation causes charge to remain within the grains in structurally unstable “electron traps”. The trapped charge accumulates over time at a rate determined by the amount of background radiation at the location where the sample was buried. Stimulating these mineral grains using either light blue or green for OSL; infrared for IRSL or heat for TL causes a luminescence signal to be emitted as the stored unstable electron energy is released, the intensity of which varies depending on the amount of radiation absorbed during burial and specific properties of the mineral.
Kenworthy , Boise State University T. Rittenour , Utah State University J. Sutfin , Boise State University W. Sharp , Berkeley Geochronology Center. Optically stimulated luminescence OSL dating is increasingly used to estimate the age of fluvial deposits.
Application of OSL dating to deposits lacking such layers remains a significant challenge. Alluvial fans along the western front of the Lost River Range in.
This project investigates the climate, landscape and archaeological history of the upper Tibetan Plateau between 50 and 11 ka, the period when Homo sapiens first ventured into oxygen-depleted centre of High Asia. The project will use existing and recently developed OSL methods in novel ways in order to date the use of lithic quarries, the construction of stone arrangements and the accumulation of surface artefact scatters.
This project further develops and applies a set of classical and novel optical dating techniques to rock fall sites and deep-seated gravitational slope deformations in alpine contexts. About us News Group Members Former Group Members. Current Research Past Projects.