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”.
Optically Stimulated Luminescence OSL dating is a dating method for Quaternary sediments and archaeological materials. The method utilises the tiny light signal the luminescence emitted from mineral grains when they are exposed to light the optical stimulation. This signal is built up through the absorption of energy from ionising radiation, emitted from radioisotopes that are present in natural sediment. The signal is reset by light, so the method determines the length of time since the sediment was last exposed to sunlight.
OSL dating is therefore applicable only to sediments that were exposed to sunlight during their last episode of transport and deposition. This permits the dating of aeolian, fluvial, shoreline and lake sediment, but not, for example, sub-glacial sediment.
As such, the optical dating methods allow the systematic chronological evaluation of Quaternary-age sedimentary sequences. Sampling for the.
Resources home v2. Introduction Services Prices. Application Central for samples up to about Lund containing quartz. Technical Geography Laboratory All sediments contain trace minerals including uranium, thorium and potassium. Water Content Calibration Water within the soil has an attenuating effect on the ambient radiation. Consequently, samples analysed without price of their water content or using a low estimate of water content will return ages younger than samples corrected for this luminescence.
Similarly, inaccurate estimates of pore water salinity will dramatically affect the results. Price The limiting factor in the age range for luminescence dating is the ‘saturation’ of the signal at large price rates i. Accurate age determination therefore becomes increasingly difficult for older samples and there is a loss in dating precision an increase in central uncertainty. The point at which a sample becomes saturated depends on the holiday rate of the sample.
Samples subjected to a high dose rate will become stimulated more quickly, and fully saturated samples will optically record the full duration of their luminescence history.
In physics , optically stimulated luminescence OSL is a method for measuring doses from ionizing radiation. It is used in at least two applications:. The method makes use of electrons trapped between the valence and conduction bands in the crystalline structure of certain minerals most commonly quartz and feldspar.
Anyway, the present situation of OSL dating methodology justifies the systematic use of SG-OSL in the dating of masonry today. Export citation.
This work is licensed under a Creative Commons Attribution 4. Dating agricultural terraces is a notoriously difficult problem for archaeologists. The frequent occurrence of residual material in terrace soils and the potential for post-depositional disturbance mean that conventional artefactual and lab-based dating methods often provide unreliable dates. In this paper we present a new technique using luminescence field profiling coupled with OSL dating to produce complete relative sequences of dates for sedimentary stratigraphies associated with agricultural terraces and earthworks.
The method is demonstrated through a series of case-studies in western Catalonia, Spain, in which we reconstruct the formation sequence of earthwork features from the Middle Ages through to the present day. The case-studies presented here show that luminescence approaches are a valuable tool to reconstruct landscape histories. DOI: Newcastle University. Home Browse Latest Policies About.
Optically Stimulated Luminescence
Optically stimulated luminescence OSL dating has proven to be extremely useful for establishing the Late Quaternary chronological framework in many areas of the Brazilian territory. In this region dominated by tropical climate, OSL dating can be more extensively applied than radiocarbon dating due to the generally low potential for the preservation of organic matter in sedimentary samples. This problem is especially critical in areas of the Amazonian lowlands, because of the hot climate and high precipitation rates.
The abundance of quartz grains deposited in fluvial and aeolian environments over this region favours OSL dating.
This paper aims to provide an overview concerning the optically stimulated luminescence OSL dating method and its applications for geomorphological research in France. An outline of the general physical principles of luminescence dating is given. A case study of fluvial sands from the lower terrace of the Moselle valley is then presented to describe the range of field and laboratory procedures required for successful luminescence dating.
The paper also reviews the place of OSL dating in geomorphological research in France and assesses its potential for further research, by focusing on the diversity of sedimentary environments and topics to which it can be usefully applied. Hence it underlines the increasing importance of the method to geomorphological research, especially by contributing to the development of quantitative geomorphology.
They are now largely used to date not only palaeontological or organic remains, but also minerals that characterise detrital clastic sedimentary material. The most common methods applied to minerals are cosmogenic radionuclides, electron spin resonance ESR and luminescence techniques. The latter were first applied to burned minerals from archaeological artefacts [thermoluminescence TL method].
Improvements of this technique led to the development, for more than twenty years, of the optical dating method [commonly referred to as Optically Stimuled Luminescence OSL ] which is now applied to sediments from various origins Wintle, The aim of this paper is to provide people involved in geomorphological research a global overview about the principles and procedures of optical dating, from the field sampling to the age interpretation. Most of the publications actually focus on one part of either the method e.
The general principles of the method are described first.
Luminescence dating is used to identify when a sample was last exposed to daylight or extreme heat by estimating the amount of ionising radiation absorbed since burial or firing. This equation very simply expresses the calculations necessary, but it is important to be aware of the factors influencing the two values used.
Heterogeneous sediments and radioactive disequilibria will increase errors on Dr, while incomplete bleaching of the sample prior to burial, anomalous fading in feldspars, and the estimation of past sediment moisture content may all also add to increased errors. The dating of sediments using the luminescence signal generated by optical stimulation OSL offers an independent dating tool, and is used most often on the commonly occurring minerals of quartz and feldspar and, as such, has proved particularly useful in situations devoid of the organic component used in radiocarbon dating.
Quartz has been used for dating to at least ka, while the deeper traps of feldspar have produced dates as old as 1 ma. The use of fine-grain dating for samples such as pottery, loess, burnt flint and lacustrine sediments, and coarse-grain dating of aeolian, fluvial and glacial sediments is regularly undertaken.
A Brief Description of Optically Stimulated Luminescence Dating. Please reference: Mallinson, D., A Brief Description of Optically Stimulated.
Description Applicability. The radiocarbon method is a traditional method for dating and correlating Quaternary deposits. However, the possibilities of its application are limited due short chronological interval of up to kyr and high requirements to the burial conditions of dated organic material. In this situation, the method of optically stimulated luminescence OSL is the only alternative to dating sediments with an age of more than 50 kyr. Method description. The OSL dating is based on the assessment of the absorbed radiation dose over the period of sediment burial.
The age is calculated by dividing the absorbed dose by the dose rate accumulation rate. One of the main advantages of the method is the wide distribution of material suitable for dating. This can be quartz or feldspar grains. The only limitation is the necessary setting to zero of the old light sum stored in mineral grains before starting the counter. Bleaching is obvious for subaerial sediments, quite real for channel, floodplain, offshore and similar sediments, but problematic for deep-water formations redeposited exclusively outside the sunlit shallow water, at depths of more than m.
Minor errors can be caused by poorly controlled diagenetic changes in rock moisture, nuclide migration, signal instability. OSL age values are usually given with standard deviations of laboratory measurements. It is believed that the reliability of OSL dating for quartz is limited to kyr.
Laboratory of optically stimulated luminescence (OSL Laboratory)
Up to now not a single dating technique has been developed for in-situ planetary exploration. The only information on the age of extraterrestrial planetary surfaces comes from the “crater-counting” method. This method has an inherent large error and low resolution and is completely inadequate for local geology. Luminescence dating has possibly the potential to open up a completely new discipline in planetary in-situ exploration.
The OSL optically stimulated luminescence dating method exploits dosimetric properties of grains of minerals naturally occurring in sediments and man-made materials. In archaeology the OSL method is used to date pottery and other heated materials e. When compared with the radiocarbon method it makes possible dating objects containing no organic matter or originating in periods for which the radiocarbon method is less accurate due to the shape or lack of the calibration curve. This paper discusses the details of recent advances in the method and several examples of its application to material from archaeological excavations of Medieval to Palaeolithic sites.
Testing Luminescence Dating Methods for Small Samples from Very Young Fluvial Deposits
Optically stimulated luminescence dating of rock surfaces. N2 – There are many examples of rock surfaces, rock art and stone structures whose ages are of great importance to the understanding of various phenomena in geology, climatology and archaeology. Optically stimulated luminescence OSL dating is a well-established chronological tool that has successfully determined the depositional age of a wide variety of fine-grained sediments, from several years to several hundred thousands of years.
on luminescence dating methods (TL or OSL) or procedures (palaeodose or dose rate determi- nations). I have attempted to make the technical discussion in.
The Luminescence Dating and Dosimetry Laboratory is developing new techniques for application to the dating of artefacts and deposits from sites that range widely in terms of chronological period, geographic location and material type. Recent work as focused on optically stimulated luminescence OSL techniques, in particular a novel experimental approach to the measurement of single grain OSL.
A study produced, for the first time, absolute dates for a range of brick stupas located within the hinterland of Anuradhapura , contributing to the further development of a brick monument chronology for the region. Ongoing work is examining whether unfired clay bricks from various sites can be dated accurately. OSL techniques are being applied to date sediment sequences in stratigraphic contexts associated with irrigation systems. In the absence of suitable organic samples for C dating, these systems are very difficult to date.
New approaches are being applied to the dating of post-Roman irrigation systems in Spain to establish when they were created and used. Also, as part of a major investigation supported by the European Research Centre and led by Prof. Sauer at the University of Edinburgh, a PhD project has started to investigate the application of OSL and geomorphological techniques to establish the chronology of irrigation systems and settlement sites associated with the demographic growth at the frontiers of the Sasanian Empire.
The availability of chronologies for aeolian horizons obtained using OSL provides a valuable tool in the study of the evolution of coastal landscape and how past coastal communities responded to climate change. The OSL dating of sands and palaeosol horizons, supported by geomorphological analysis, has identified critical stages in the development of the landscape on Herm on which megalithic monuments were constructed during the Neolithic period. The OSL dates identified three phases of significant aeolian activity during the prehistoric period, the onset dated to ca , and years ago and evidence of ploughing activity was placed in the late 2nd millennium BC and in the 4th and 13th centuries AD.
The testing of sediments directly associated with structures and monuments on Herm continues. Contrary to the expectation of in situ burial indicated by earlier research, the cultural deposits were probably displaced from their primary context by processes associated with the development of the solution feature and this has important implications for establishing the timing of hominin use of the upland areas.
Luminescence Dating: Applications in Earth Sciences and Archaeology
Please reference: Mallinson, D. Optically stimulated luminescence is a method of determining the age of burial of quartz or feldspar bearing sediments based upon principles of radiation and excitation within crystal lattices, and stems from the fact that imperfections in a crystal lattice have the ability to store ionizing energy Aitken , ; Botter -Jensen et al. Radiation within sediments comes from alpha, beta, and gamma radiation emitted during the decay of U, U, Th, 40 K, and 87 Rb, and their daughter products, both within the mineral grains and in their surroundings Lian , , and from cosmic rays Figure 1.
Under controlled laboratory conditions, assuming the sample was collected under light-restricted conditions, controlled exposure of the sample to photons yields a luminescence response the equivalent dose, D e , the intensity of which is a function of the dose rate within the sediment, and the length of time the sample was exposed to the background radiation. In order to measure the age, two factors must be known; 1 the environmental dose rate, and 2 the laboratory dose of radiation that produces the same intensity of luminescence as did the environmental radiation dose the equivalent dose.
Dividing the equivalent dose by the dose rate yields time.
Scientists in North America first developed thermoluminescence dating of rock minerals in the s and s, and the University of Oxford, England first developed the thermoluminescence dating of fired ceramics in the s and s. During the s and s scientists at Simon Frasier University, Canada, developed standard thermoluminescence dating procedures used to date sediments.
In , they also developed optically stimulated luminescence dating techniques, which use laser light, to date sediments. The microscopic structure of some minerals and ceramics trap nuclear radioactive energy. This energy is in constant motion within the minerals or sherds. Most of the energy escapes as heat, but sometimes this energy separates electrons from the molecules that make up the minerals or ceramics.
Usually the electrons will reconnect with the molecules, but some will not. The electrons that dont reconnect eventually encounter imperfections in the microscopic structure of the ceramics or minerals, and they become trapped by these imperfections. Over time energy in the form of more and more trapped electrons is stored in these structural imperfections. By heating the ceramic or mineral to above degrees Celcius, these trapped electrons are released, creating a flash of light called thermoluminescence.
When a laser light source is used to stimulate the release of electrons, the process is called optically stimulated luminescence. Luminescence Profile In the process of making a ceramic vessel, the soft clay vessel must be heated in a kiln to harden it.