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Optically stimulated luminescence dating

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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.

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SEE VIDEO BY TOPIC: How to date archaeology sites if you don't have carbon: OSL 101 Lowery amerikancilar.com4

Optically Stimulated Luminescence (OSL) Dating

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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.

This is followed by a look at measurement equipment that is employed in determining age and its operation. Luminescence properties of minerals used in dating are then examined after which procedures used in age calculation are looked at. Sample collection methods are also reviewed, as well as types of materials that can be dated. Continuing refinements in both methodology and equipment promise to yield luminescence chronologies with improved accuracy and extended dating range in the future and these are briefly discussed.

Luminescence - An Outlook on the Phenomena and their Applications. Luminescence dating refers to age-dating methods that employ the phenomenon of luminescence to determine the amount of time that has elapsed since the occurrence of a given event.

In this chapter, the application of luminescence techniques in dating geological and archaeological events is examined. Generally, the term luminescence dating is a collective reference to numerical age-dating methods that include thermoluminescence TL and optically stimulated luminescence OSL dating techniques. Other terms used to describe OSL include optical dating [ 1 ] and photon-stimulated luminescence dating or photoluminescence dating [ 2 ].

Luminescence dating methods are based on the ability of some dielectric and semiconducting materials to absorb and store energy from environmental ionizing radiation. In earth sciences and archaeological applications, the dielectric materials are usually minerals such as feldspar and quartz.

Environmental ionizing radiation for earth science and archaeological applications typically comes from radioactive elements within the immediate surroundings of the mineral grains as well as from cosmic radiation. When the minerals are stimulated, they release the stored energy in the form of light, from which the term luminescence is derived.

Stimulation of energy release by heating is referred to as TL. When light is used, on the other hand, the technique is described as OSL. Measuring the amount of energy released in conjunction with a determination of the rate at which the energy was accumulated allows an age to be calculated, indicating time that has elapsed since the storage of energy began.

Luminescence methods can generally be used to date materials that range in age from a few decades to about , years. However, ages of up to several hundred thousands of years have been reported in some studies [ 4 ]. Therefore, the method can be used for dating events of Late Pleistocene and Holocene age ca.

Radiocarbon dating is a technique that can also be used to date some materials of Late Pleistocene or Holocene age if they bear carbon. Hence, when dealing with materials that do not contain organic carbon, luminescence dating can serve as an optional chronometer to radiocarbon dating. This chapter presents a brief examination of how luminescence is used in earth sciences and archaeology to measure time.

In both fields of study, the imperativeness of assigning a temporal scale to events and processes is an inherent aspect of the discipline. Hence, the role played by dating cannot be overstated. The chapter is not intended to be used as a practice manual. Rather, the aim is to provide a primer that acquaints scholars who may be familiar with the science of luminescence but are not accustomed to its application as a dating method.

Thus, the chapter comprises eight sections. Following an introductory look at the development of luminescence dating in Section 1, principles of luminescence dating are examined in Section 2. In Section 3, basic luminescence measurement equipment and sample stimulation mechanisms during measurement are explored after which luminescence properties of some common minerals are examined.

The determination of parameters used in the luminescence age equation is discussed in Section 5, and this is followed by a look at materials that can be dated with luminescence methods in Section 6.

Section 7 looks at methods used in sample collection and preparation prior to the analysis. In Section 8, the chapter concludes with a look at future developments in luminescence dating. The ability of some minerals to luminesce when stimulated is not a recent finding.

The earliest recorded observation of the behavior in minerals has been attributed [ 5 ] to Robert Boyle, who in recounted his discovery [ 6 ] that a diamond that had been loaned to him could emit light when heated.

The focus of this section, however, is not on the history of the science of luminescence but rather on the history of the emergence of the application of luminescence as a dating technique for geological and archeological materials. That inception can be traced back to approximately seven decades ago, to a period during which experiments were being conducted into applications of TL [ 8 , 9 ].

Zeller et al. Progress in dating geological materials, however, was hampered by a limited understanding of the luminescence process in rocks and accurate ages were hard to come by [ 11 ].

It is in the dating of heated archaeological artifacts that progress was realized. In , Daniels et al. Subsequently, Kennedy and Knoff [ 13 ] provided some basic aspects of dating heated archaeological materials using TL, though the approach had not been tested on actual samples as yet.

Around the same time, Grogler et al. It was in that Aitken et al. Results demonstrated that the luminescence intensity emitted by the samples was linearly proportional to radiocarbon ages of sediments from which the samples were obtained. The positive results noted in these early studies gave impetus for further refinements in TL protocols, and throughout the rest of the s and s, the dating method gained a foothold in archaeological studies.

A major development in luminescence studies occurred when TL dating was extended to determining burial ages of unheated sediments. The evolution appears to have followed two parallel paths, one in the West and another in former Eastern Bloc countries. However, it seems there was minimal interaction between the two geographical regions, especially in the early stages. In the West, some of the earliest work includes a study [ 15 ] that looked at TL signals of deep-sea sediment that mostly comprised foraminiferal shells.

The investigators [ 15 ] considered the signals to be from calcite and noticed that the TL intensity increased with depth. Later, another study [ 16 ] investigated a deep-sea sediment core that comprised predominantly siliceous plankton and reported results similar to those presented earlier [ 15 ].

Subsequent studies by Wintle and Huntley [ 17 ] provided additional TL data from deep-sea sediments that also showed increasing signal intensities with depth. However, it was later observed [ 17 ] that the TL signals from deep-sea cores actually came from detrital minerals that were mixed with the plankton. Significantly, it was also suggested [ 17 ] that what was being dated was the last time the ocean sediments had been exposed to sunlight.

Though it was some time before researchers fully understood the zeroing mechanism for unheated sediment [ 18 ], that discovery was extremely important for sediment dating since it meant that the exposure of sediments to sunlight had the same zeroing effect of accumulated energy in sediment grains as did heating in pottery.

In former Eastern Bloc countries, the analysis of unheated terrestrial sediments using TL appears to have begun sometime during the s. Early published reports from the former Soviet Union include a study [ 19 ] that examined TL signals of Quaternary deposits. A few years later, Morozov [ 20 ] presented relative ages of Quaternary sediments from Ukraine that had been dated using TL methods. The study was mainly based on the recognition that luminescence signal intensities increased with depth, which was interpreted as commensurate with age.

Morozov [ 20 ] also suggested that the signal was coming from quartz in the sediments. Shortly afterwards, Shelkoplyas [ 21 ] reported a range of Quaternary TL ages obtained from soils and loess deposits [ 18 ]. Throughout the s, researchers in Eastern Bloc countries [ 22 — 29 ] as well in China [ 30 ] reported studies in which TL was used to date Quaternary deposits.

The accuracy of some of these early ages, however, is questionable [ 18 ], not least because zeroing mechanisms were not well-understood at the time. In other studies, efforts were directed at understanding TL characteristics of dosimeters, especially quartz [ 31 — 33 ]. Around the time Wintle and Huntley [ 17 ] discovered that TL signals in their deep-sea cores were coming from detrital mineral grains mixed with the plankton, they became aware of the work by Eastern Bloc researchers who had worked extensively with terrestrial sediments.

Ultimately, they realized that TL dating could be applied much more broadly to date Quaternary deposits [ 18 ]. These developments resulted in the landmark publications by Wintle and Huntley [ 17 , 34 , 35 ] in which TL dating of sediments was outlined.

With increased research throughout the early s, dating procedures improved as efforts were made to standardize procedures [ 18 ]. However, optimal conditions for solar resetting of sediments remained unclear to researchers and this hampered the accuracy of TL ages. Researchers who examined the problem include Huntley [ 36 ] who investigated solar resetting of sediments from various environments and proposed a method to address the issue of inadequate zeroing.

By , another monumental step in luminescence dating would be realized when Huntley et al. This led to the development of OSL dating which offered a number of advantages over TL methods when dating unheated sediments.

With further equipment and methodological refinements, there was a burgeoning of OSL dating studies of Quaternary sediments throughout the s that saw luminescence dating emerge as a robust dating technique. Over the last two decades, the technique has developed further [ 37 — 39 ], and today, it is the method of choice for dating detrital sediments of Late Pleistocene and Holocene age as well as previously heated archaeological artifacts.

Many minerals such as quartz, feldspar, calcite and zircon are dielectric materials and, when subjected to ionizing radiation, they are able to store energy in their crystal lattices. In natural geological and archeological settings, the ionizing radiation emanates naturally from the immediate surroundings of the minerals. Cosmic radiation may also contribute a small component.

If the minerals used in dating are stimulated, they release the energy by luminescing and, within certain constraints, the energy released is proportional to the stored energy. In luminescence dating, the energy given out by the minerals or dosimeters following stimulation is measured using appropriate instrumentation. This energy is referred to as the paleodose [ 50 ]. In order to determine an age, the rate at which the energy was accumulated by the dosimeter, or the dose date, is also ascertained.

The quotient of the paleodose and the dose rate, as indicated in Eq. If the mineral grains were emptied of all previously accumulated energy prior to the latest energy storage episode, the age obtained will denote time that has elapsed since the start of that episode.

Hence, both in geology and archaeology, the luminescence age simply connotes time that has passed since the occurrence of a specific energy zeroing event.

In geology, this might be a geomorphic event that exposed sediment to sunlight. Zeroing by sunlight is also sometimes referred to as optical bleaching [ 3 ]. In pottery, zeroing would normally occur during a firing event associated with the manufacture. Mechanisms by which minerals store energy in their crystal lattices as a result of ionizing radiation are complex [ 50 — 52 ].

However, it is thought that ionizing radiation drives mineral crystals into a metastable state where electrons are displaced from their parent nuclei. The positions from which the electrons have been evicted act as holes. The electrons and holes then diffuse within the mineral crystals and become trapped separately at lattice defects.

Examples of common defects include a negative ion missing from its lattice position, a negative ion positioned in an interstitial site or the presence of impurity atoms in the lattice through substitution [ 52 ].

Other more complex trap types exist [ 52 ]. Stable traps are those that can withstand perturbations such as lattice vibrations that could dislodge the electrons from their traps.

If the crystal lattice is stimulated using an appropriate mechanism, for example, by heating to an adequately high temperature or by exposure to an optical source with a suitable wavelength, trapped electrons will be evicted out of the traps. Once evicted, the electrons diffuse within the crystal lattice until they reach a site that is attractive to electrons.

Luminescence dating

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.

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.

Portable Spectrofluorimeter for non-invasive analysis of cultural heritage artworks using LED sources. Luminescence spectroscopy - Spatially resolved luminescence - Time resolved luminescence - Electron spin resonance ESR. Flint and heated rocks - Ceramics and pottery - Unheated rock surfaces - Tooth enamel and quartz grains - Sediment dating. LexEva is a newly released evaluation software developed for analysis in luminescence research and dating. Few years depending on signal intensity and sensitivity of equipment for which the lexsyg systems are especially developed.

Luminescence Dating: Applications in Earth Sciences and Archaeology

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.

Optically Stimulated Luminescence

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. A certain percent of the freed electrons become trapped in defects or holes in the crystal lattice of the quartz sand grain referred to as luminescent centers and accumulate over time Aitken,

Optical : Relating to the use of visible or near-visible light.

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.

Optically stimulated luminescence

Jain Mayank, Murray A. Optically stimulated luminescence dating: how significant is incomplete light exposure in fluvial environments? In: Quaternaire , vol.

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. The ionizing radiation produces electron-hole pairs: Electrons are in the conduction band and holes in the valence band. The electrons that have been excited to the conduction band may become entrapped in the electron or hole traps.

Optically stimulated Luminescence dating of quartz

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. Samples for OSL analysis are typically collected from opaque core tubes aluminum or black pvc tubes that are pushed into the sediment using coring equipment vibracore , geoprobe , etc. Samples are then extracted for processing under dark-room conditions.

Optically stimulated luminescence (OSL) is a technique used to date fossils in geological sediments through ionized radiation to determine the last time a mineral.

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Но с ключа могут снять копию. - Каждый, кто к нему прикоснется, будет уничтожен. Повисла тишина.

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Сьюзан рассказала Дэвиду про КОМИ НТ, подразделение глобальной разведки, в распоряжении которого находилось немыслимое количество постов прослушивания, спутников-шпионов и подслушивающих устройств по всему земному шару.

Беккер изумился. - Un punqui. - Si. Punqui. - Панк.

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Comments: 3
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