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 dating of young quartz using the fast component
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. More than 20 years of continuous and collaborative work has resulted in the creation of an extensive OSL age database for Late Quaternary sedimentary deposits in the Amazonian lowlands.
Initial quartz optically stimulated luminescence (OSL) dating For all measurements we compared two approaches to define the net OSL.
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.
Most luminescence dating methods rely on the assumption that the mineral grains were sufficiently “bleached” at the time of the event being dated. Single Quartz OSL ages can be determined typically from to , years BP, and can be reliable when suitable methods are used and proper checks are done.
Luminescence Dating: Applications in Earth Sciences and Archaeology
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.
Optical dating is an umbrella term for an armada of acronyms, the most common in archaeological contexts being. OSL (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, 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.
Optically Stimulated Luminescence (OSL) Dating in the Amazonian Wetlands
Optically stimulated luminescence dating at Rose Cottage Cave. A single-grain analysis demonstrates that the testing procedure for feldspar fails to reject single aliquots containing feldspar and the overestimate of age is attributed to this. Seven additional luminescence dates for the Middle Stone Age layers combined with the 14 C chronology establish the terminal Middle Stone Age deposits at 27 years ago, while stone tool assemblages that are transitional between the Middle Stone Age and the Late Stone Age are dated to between 27 years and 20 years ago.
Although there are inconsistencies in the Middle Stone Age dates, the results suggest that the Howiesons Poort at Rose Cottage Cave dates to between 70 years and 60 years ago. Much of the rich archaeological heritage in southern Africa is older than 50 years, which is the limit of the ubiquitous 14 C dating technique.
Optically stimulated luminescence (OSL) dating has become one of the transition at RCC is clearly defined at 20 years ago by 14C dates.
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. If we assume that the radiation dose rate of the sediment has remained constant over time, then if we measure that dose rate, we can calculate the sample age.
Jain Mayank, Murray A. Optically stimulated luminescence dating: how significant is incomplete light exposure in fluvial environments? In: Quaternaire , vol.
and offers a broad spectrum of luminescence dating capabilities, including optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques.
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.
Optically stimulated luminescence
From the conduction band they may recombine with holes trapped in hole materials. If the centre with the hole is a luminescence center radiative recombination centre emission of light will occur. The photons are detected may a photomultiplier tube. The signal from the tube is then used to calculate the dose that the material had absorbed. The OSL dosimeter provides a new degree of sensitivity by giving an accurate reading as low as 1 mrem for laboratories and gamma ray photons with energies ranging from 5 keV to greater than 40 MeV.
The OSL dosimeter’s maximum equivalent dose measurement for x-ray and gamma ray photons is rem.
1mm). OSL optically stimulated luminescence. P palaeodose, another term used for equivalent dose (De) ppm parts per million (10,ppm = 1%). Ra. Radium.
Optically stimulated luminescence and isothermal thermoluminescence dating of high sensitivity and well bleached quartz from Brazilian sediments: from Late Holocene to beyond the Quaternary? E-mail: andreos usp. E-mail: ligia. E-mail: ccfguedes gmail. E-mail: wsallu gmail. E-mail: assine rc. The development of optically stimulated luminescence OSL dating of sediments has led to considerable advance in the geochronology of the Quaternary. OSL dating is a well established technique to determine sediment burial ages from tens of years to few hundred thousand years.
Recent studies have shown that Quaternary sediments of Brazil are dominated by quartz grains with high luminescence sensitivity, allowing the determination of precise and reliable OSL burial ages. We discuss the OSL data and ages of sediments from carbonate and terrigenous distributary and tributary systems fluvial depositional contexts in Brazil.
Most of the studied fluvial sediments show equivalent dose distributions with low to moderate dispersion, suggesting well bleached sediments. The comparison between aliquot and single grain data suggests that high overdispersion in equivalent dose distributions of some samples is more related with sediment mixture due to bioturbation than with incomplete bleaching during transport.
Alastair C. We have attempted to isolate the fast component of the quartz optically stimulated luminescence OSL signal using a curve-fitting procedure. By pre-determining the decay constants, the procedure is simple enough to be scripted, allowing a large number of aliquots to be processed. A Monte Carlo error routine is used, in which simulated decay curves are fitted with several exponentials, which vary in their decay rates according to the measured distributions of fast and medium component decay rates.
The derived error term is closely related to the intensity of the fast component signal, but is also influenced by the degree of similarity between the equivalent doses of the fast and medium OSL components. There are potential advantages in using this procedure to date both well-bleached and partially bleached quartz, of any depositional age.
luminescence (OSL) dating of quartzite cobbles from the Tapada do Montinho archaeological site (east- The long-term water contents of sediment samples.
David Sanderson, Timothy Charles Kinnaird. Discover related content Find related publications, people, projects and more using interactive charts. Research at St Andrews. Section navigation. Abstract This chapter concerns the use of luminescence methods as geochronological tools for dating Late Quaternary sediments in the Red Sea region. The dating methods all use stimulated luminescence to register signals developed in mineral systems in response to long term exposure to ionising radiation in the environment.
The principles of luminescence dating are outlined followed by discussion of its application to the Arabian Peninsula, where, particularly in SE Arabia and parts of the interior, a growing corpus of work is emerging, which is helping to define past arid or humid periods of importance to palaeoclimatology and to archaeology. The motivation for much of this work concerns definition of the environmental conditions and chronologies for hominin and human dispersion through Arabia.
Results are also presented from the littoral fringe of southwest Saudi Arabia, identifying units associated with MIS5 which have palaeo-environmental and archaeological significance. It is to be hoped that further research in coming decades will continue to extend the regional chronology for the littoral fringe of the Red Sea. In this respect, luminescence dating has the potential to help define the environmental history of this important area, to assist with assigning marine and terrestrial features into unique stages of Quaternary climate cycles, and to promote better understanding of human-environment interactions in this dynamic area.
View graph of relations. Related by author Multi-proxy characterisation of the Storegga Tsunami and its impact on the early Holocene landscapes of the southern North Sea Gaffney, V.