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.
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.
However, there is no routine OSL dating method applicable to larger clasts such as cobbles, boulders and other rock surfaces. Here the application of quartz OSL to the dating of rock surfaces is successfully tested by application to two different quartz-rich rock types sandstone and quartzite. Together with the measurement of infrared stimulated luminescence IRSL signals as a function of depth into the surface of different granites it is clear that both OSL and IRSL can be fully reset in the two mm closest to the rock surface.
Introduction. Luminescence dating is a geochronological technique used to directly date geological events and archeological artifacts from the late Quaternary.
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
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 Optically Stimulated Luminescence Dating (OSL) technique determines the burial age of sedimentary deposits. This method utilizes he.
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, In our laboratory, these sediments are exposed to an external stimulus blue-green light and the trapped electrons are released.
The released electrons emit a photon of light upon recombination at a similar site. In order to relate the luminescence given off by the sample to an age, we first need to obtain the dose equivalent to the burial dose. Following the single-aliquot regenerative SAR method of Murray and Wintle , the dose equivalent De is calculated by first measuring the natural luminescence of a sample.
Then, the bleached sample is given known laboratory doses of radiation, referred to as regenerative doses. The regenerative dose data are fit with a saturating exponential to generate a luminescence dose-response curve. The De is calculated by the intercept of the natural luminescence signal with the generated curve. A curve is generated for each aliquot subsample , multiple aliquots are needed to obtain an accurate De.
Luminescence and ESR Dating
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.
Luminescence dating is a chronological method that has been used extensively in archaeology and the earth sciences. It is based on the emission of light.
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.
The principles of Luminescence Dating
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.
Improvements of this technique led to the development, for more than twenty years, of the optical dating method [commonly referred to as Optically Stimuled.
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.
This assessment has a strategic value for the development of a new generation of in-situ instrumentation. Sedimentation processes on Mars are completely unexplored. In addition, fluid phases may have contributed significantly to erosion and transport processes to form the Martian landscape. Dating of buried grains in sedimentary layers would give a crucial contribution to the understanding of surface forming processes and is essential for any further exploration of planet Mars.
It is therefore essential to develop a method, which can determine the chronology of sedimentary deposits.
All Research Projects
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 disagreement between OSL and 14C ages it suitable for luminescence dating. The OSL samples were pretreated following the aforementioned method.
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.
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Optically Stimulated Luminescence
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
recognised as an important technique for establishing a time frame of deposition of sediments. (Aitken, ). Optical dating differs from thermoluminescence.
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.