Research Spending & Results
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.
Optically Stimulated Luminescence
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.
The DRI E. The DRILL is a research laboratory dedicated to fundamental investigations in the luminescence properties of earth materials, and to the application of luminescence dating techniques to geomorphological, geological, and archeological problems. The DRILL welcomes collaboration with research institute and university faculty, consultants, and government agency researchers. The DRILL research staff can collaborate on proposals, contribute to grant writing, and consult on study design.
We can also arrange training for undergraduate and graduate students, post-docs, and visiting researchers.
Luminescence dating is a scientific method which dates certain artifacts vessel is fired or when rocks are heated) empties the stored energy.
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.
Lund Luminescence Laboratory
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.
The Optically Stimulated Luminescence Dating (OSL) technique error and low resolution and is completely inadequate for local geology.
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. This is followed by sieving, heavy liquid Li- or Na- polytungstate separation, and sometimes magnetic separation to concentrate quartz sands of the appropriate size. All of the processing must be done under dark-room conditions.
Optically stimulated Luminescence dating of quartz
Beach ridges that form during seaward migration of a shoreline indicate the successive positions of past shorelines; their age and distribution can therefore provide a geological record of past coastal changes Tamura, Because beach-ridge deposits generally lack material suitable for radiocarbon dating e. The Yumigahama Peninsula is a sandy coastal barrier with a well-developed sequence of beach ridges Sadakata, An immense increase in sediment discharge from the catchment of the neighboring Hino River in response to 17 th and 18 th century mining of iron for the manufacture of swords Sadakata, ; Tokuyasu, enhanced sediment deposition that caused rapid seaward migration of the shoreline and the development of a sequence of ridges.
Absolute dating of the ridge sediments will help to quantify the effect of human activity on the geomorphology of this region.
The luminescence dating techniques estimate the time of the most recent ‘zeroing’ geologist/geomorphologist about the time-averaged water-content over the.
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. Such a technique must be incorporated into an instrument requiring low resources mass, power, volume and placed onto the surface of Mars.
Since various sites on the Martian surface need to be visited, the instrument must be incorporated into a mobile surface rover having a soil penetration capability or a sample retrieval system. The OSL method has been demonstrated its suitability in portable instruments during the fieldwork in sedimentary deposits on Earth.
The principles of Luminescence Dating
Luminescence dating is a geochronological technique that spans the Late Quaternary. It is particularly useful for minerogenic sediments, for example as optically stimulated luminescence OSL dating of quartz and infrared stimulated luminescence IRSL dating of feldspar. Thermoluminescence TL dating can also be used to determine the age of pottery. The Lund Luminescence Laboratory was established in , as the first of its kind in Sweden. In the adjoining rooms mechanical and chemical preparation of samples can be carried out under darkroom conditions.
of tidal rhythmites in the geologic record. Initial quartz optically stimulated luminescence (OSL) dating feasibility studies have concentrated on.
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.
How glowing sediment can help to decipher the Earth’s past climate !
Jack Rink about a new technique that he using to determine the age of the Crystal River archaeological site. He began his education in Florida where he received his Ph. After working on projects in Africa, Europe and Asia, Dr. Rink returned to Florida several years ago to work on the Salt Springs site near Palatka.
luminescence for dating purposes is, so far, mainly limited to quartz and feldspar. This is due to their abundance in sediments at most geological settings, as well.
The last 2. To be able to fully understand and interpret past climate variations the development of accurate and precise chronological techniques is crucial. Optically stimulated luminescence OSL dating is a strong geochronological tool that can be used to date across a wide time range, from the modern days to a few hundred thousand years ago.
It has been used to date sediments in nearly all parts of the world. The event that is being dated is the last time the sediment has been exposed to daylight, which means that the luminescence age is directly related to the time of sediment deposition. OSL dating is based on the ability of minerals to store energy Preusser et al.
They work like small batteries, which get charged when the sediment is buried Fig. This is due to radiation from naturally occurring radioactive material uranium, thorium and potassium in the surrounding sediment, and from cosmic rays for samples closer to the surface. Like a battery, the quartz and feldspar grains have a finite capacity for storing energy.
Once completely charged, the battery-like grain is considered as being saturated. This upper age limit of OSL dating depends on the ability of the grain to store the energy and on the rate at which the grain is charged i. If the surrounding material is very radioactive, the dose rate is very high, which means that the grain saturates rather quickly Fig.
Exposure to natural sunlight will remove charge from the grain. This bleaching or resetting occurs e.
‘ + $(h2).text() + ‘
D granting institution. The OSL lab at NMHU will support research that will benefit from the ability to date the burial ages of silicate phases in geological and archaeological materials up to several hundreds of thousands years before present. The instrument will support Quaternary investigations of the timing and extent of past glaciations and subsequent retreat and the influence of past climate on plant and animal life and human evolution and distribution.
The OSL lab will be the first of its kind in the state of New Mexico and will support experiential laboratory training for a student population dominated by Hispanic students. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
OSL dating is a system of sampling and measuring the amount of energy that is trapped within The crystals serve as a geologic stop watch.
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.