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In Southern African Prehistory and Palaeoenvironments, ed.
Radiocarbon 12 , Radiocarbon 1 , On a new radiocarbon chronology for Africa south of the Equator, Part 1. Luminescence dating at Rose Cottage Cave: Late Pleistocene technology at Rose Cottage Cave: The role of diversity in the evolution of symbolic behaviour: D thesis, University of the Witwatersrand, Johannesburg. National Research Foundation Final Report: A review of quartz optically stimulated luminescence characteristics and their relevance in single-aliquot regeneration dating protocols.
Radiation Measurements 41 , Optical dating of young modern sediments using quartz: Thermoluminescence dating of partially bleached sediments. Nuclear Tracks and Radiation Measurements 10 , Developments in radiation, stimulation and observation facilities in luminescence measurements. Testing optically stimulated luminescence dating of sand-sized quartz and feldspar from fluvial deposits. Measurement of the equivalent dose in quartz using a regenerative-dose single-aliquot protocol. Radiation Measurements 29 , Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: Part II, Results and implications.
Archaeometry 41 , Precision and accuracy in the optically stimulated luminescence dating of sedimentary quartz: Geochronometria 21 , An Introduction to Optical Dating. Oxford University Press, Oxford. Distinguishing quartz and feldspar in single grain luminescence measurements. Optical dating of dune sand from Blombos Cave, South Africa: I - multiple grain data. Evaluation of SAR procedures for D e determination using single aliquots of quartz from two archaeological sites in South Africa.
Towards the development of a preheat procedure for OSL dating of quartz. Part I, Experimental design and statistical models.
Ancient TL 16 , Optical dating of young sediments using fine-grain quartz. Ancient TL 13 , Reporting of 14 C data. Radiocarbon 19 , Radiocarbon 46 , Van der Plicht J. High-precision radiocarbon age calibration for terrestrial and marine samples. Radiocarbon 40 , A simplified approach to calibrating 14 C dates. Radiocarbon 35 , IntCal98 radiocarbon age calibration, 24 cal BP. Luminescence dating in less than ideal conditions: Electron-spin resonance dating from Klasies River Mouth Cave. Earliest modern humans in South Africa dated by isoleucine epimerization in ostrich eggshell.
University of Florence Press, Florence. This article is accompanied by supplementary tables and figures online at www.
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Aliquots from samples RCC , 18, 19 and 21 were assessed against OSL rejection criteria that were assumed to eliminate most errors derived from the OSL behaviour and sedimentary history of the grains see Table 1 in supplementary material online. The first and probably the most important test is termed the dose recovery test. Dose recovery experiments 24,25 were performed on six aliquots per sample.follow site
The recovery ratios were above 0. Recuperation, or 'charge transfer', is the trapping of electrons in the OSL-related traps when they are ejected from non-OSL traps during heat treatment preheating. This phenomenon can result in unacceptable variability in D e values. Scatter in the equivalent dose measurements can result from feldspar grains that have not been eradicated during pre-treatment. Feldspar contamination in quartz aliquots can result in overestimated D e values because of the potassium contribution to the internal dose, or it can result in an underestimation of D e if anomalous fading has taken place.
Any depletion of the signal measured would be the result of feldspar contamination. Figure A see supplementary material online shows the OSL IR depletion ratio test for un-etched aliquots of RCC 6 using a large 5 mm mask; a 2-mm mask and the results of aliquots of the same sample that was etched in HF acid.
The recycling ratio R-ratio test was used to check reproducibility within the SAR measurement cycle. In practice, less than two standard deviations from unity is acceptable. The test used to establish adequate bleaching is the D e t method. If the sample is partially bleached, then the slower bleaching components yield a greater residual signal.
This test calculates D e as a function of stimulation time using approximately 0.
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The results indicated that no partial bleaching had occurred. Partial bleaching would be anticipated with fluvial deposition or weathered spall contamination, and the results seem to indicate a predominantly aeolian mode of deposition see Fig.
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After all rejection criteria 4 have been met, the remaining aliquots were subject to a preheat plateau test. For each aliquot the D e value was plotted against preheat temperature to establish if the thermal treatment was too passive and did not adequately remove the unstable signal components. This was a test of the appropriateness of the preheat protocol; where a plateau was not established in a given preheat temperature range, all aliquots preheated in that range were rejected. The final assessment was of the distribution of D e values in the form of over-dispersion values 31 see Table 1 online and a visual assessment in radial and probability density plots.
With the exception of RCC 21 see Fig. C online , all the samples were scattered evenly around a central mean so the central age model was used 33 to determine the D e values. This method used the same protocol as the multi-grain aliquots except that a laser was used to stimulate individual grains. The logic behind the single-grain analysis is to separate different populations of grains from a sample of mixed age and in this way explain the observed over-dispersion.
A total of grains were analysed, but in the case of RCC 21 the analysis did not show a mixed population. The HF etch appeared not to have removed all feldspars, but the IR-depletion test on the aliquots did not identify the problem with any accuracy. The result of the single-grain analysis indicated that the high D e values in the single-aliquot analysis were the result of feldspar contamination.
It is not clear why the feldspar test was more effective using laser stimulation on individual grains than using diode stimulation on aliquots. Because the single aliquots for RCC 21 must also have contained feldspar, and the feldspars led to D e overestimations, it was more appropriate to apply a minimum age model.
The dose rate was measured using a variety of methods. Thick source alpha counting TSAC analyses were done in the Pretoria laboratory, field gamma spectrometer measurements FGS were conducted for some of the samples with an Aptec system at the time of sampling, and high-resolution gamma spectrometer measurements HRGS were performed on a set of samples sent to Denmark for analysis by A. The large error in the water content estimation is assumed to cover the range of variability that might have occurred had the site been substantially wetter than the present from time to time.
The ratios averaged at 0. The XRF technique measured the average K concentration of the bulk sample taken back to the laboratory, whereas FGS integrated the gamma spectrum from a sphere of approximately 30 cm radius in situ in the locale from which the sample was removed. A possible cause might be the inhomogeneous distribution of K due to the large numbers of hearths present in the archaeological record. The contribution of alpha radiation is assumed to be negligible on samples that were subject to HF etching.
The result from single-grain analysis of RCC 21 illustrates that feldspars were not entirely removed by the HF treatment and the possibility that the outer surface of quartz grains was not completely etched must be considered. Where both etched and un-etched material was analysed, the latter was preferred on the basis of the better dosimetry. Only sample RCC 8 produced a statistically distinct date using the etched and un-etched material, and the latter was more closely aligned with RCC 12 date from the same layer.
Optically stimulated luminescence dating at Rose Cottage Cave S. All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License. Services on Demand Article. English pdf Article in xml format Article references How to cite this article Automatic translation. Cited by Google Similars in Google. 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. 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.
The concept of using luminescence dating in archaeological contexts was first suggested in by Farrington Daniels, Charles A. Boyd, and Donald F. Saunders, who thought the thermoluminescence response of pottery shards could date the last incidence of heating. In , Aitken et al. In , the principles behind optical and thermoluminescence dating were extended to include surfaces made of granite, basalt and sandstone, such as carved rock from ancient monuments and artifacts.
Ioannis Liritzis , the initiator of ancient buildings luminescence dating, has shown this in several cases of various monuments. The radiation dose rate is calculated from measurements of the radioactive elements K, U, Th and Rb within the sample and its surroundings and the radiation dose rate from cosmic rays.
The dose rate is usually in the range 0. The total absorbed radiation dose is determined by exciting, with light, specific minerals usually quartz or potassium feldspar extracted from the sample, and measuring the amount of light emitted as a result. The photons of the emitted light must have higher energies than the excitation photons in order to avoid measurement of ordinary photoluminescence.
A sample in which the mineral grains have all been exposed to sufficient daylight seconds for quartz; hundreds of seconds for potassium feldspar can be said to be of zero age; when excited it will not emit any such photons. The older the sample is, the more light it emits, up to a saturation limit.
The minerals that are measured are usually either quartz or potassium feldspar sand-sized grains, or unseparated silt-sized grains. There are advantages and disadvantages to using each.
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For quartz, blue or green excitation frequencies are normally used and the near ultra-violet emission is measured. For potassium feldspar or silt-sized grains, near infrared excitation IRSL is normally used and violet emissions are measured. Unlike carbon dating , luminescence dating methods do not require a contemporary organic component of the sediment to be dated; just quartz, potassium feldspar, or certain other mineral grains that have been fully bleached during the event being dated.