ESR dating of quartz extracted from Quaternary sediments application to fluvial of the Electron Spin Resonance (ESR) method and its application to the dating of . Among the available materials, the potential of quartz is important for dating. Subdepartment of Quaternary Research, University ef Cambridge, Free School Lane, Cambridge CB2 electron spin resonance (ESR) dating; this method is. Here, the electron spin resonance (ESR) dating method is often the only one only one method permitting to place these localities in the global Quaternary ESR can be applied on different materials frequently recovered in.
Various procedures were proposed for this determination. First, Yokoyama et al. The main difficulty of this way concern the choice of this sediment, which needs to have the same general characteristics of the fossil one.
More recently, the study of the bleaching curves of fossil samples has permitted to propose mathematical functions describing the decrease of Al-center intensity versus the light-exposure time Wal- ther et Zilles, ; Toyoda et al, ; Voinchet et al, In practice, the observed decreasing curve can be expressed by a double exponential function and the maximal bleaching is done by exposing the quartz samples under an ultra-violet light during a six months equivalent-time fig.
This period could appear to be long, but a study performed on present fluvial deposits has permitted to confirm that the maximal bleaching was really reached fig. This validates the use of ESR dating of alluvial deposits. Sampling and experimental The sediments are sampled in cleaned sections in order to minimize parasite bleaching.
In the lab, a im fraction is selected by water sieving. Quartz is then separated using a chemical and physical protocol already detailed in the literature Yokoyama et al, ; Laurent et al, ; Voinchet, After this treatment, the sample is split in several aliquots used for the residual dose and total dose determinations. Irradiation is performed using a panoramic 60Co source Dolo et al, emitting a 1.
Quaternary dating by electron spin resonance (ESR) applied to human tooth enamel
Generally, height aliquots are submitted to doses ranging between and 30, Gy. The determination of the residual intensity is realized with the experimental device described in Voinchet et al Three halogen lamps and one UV lamp imitating the solar spectrum were used to illuminate the quartz grains.
The light intensity then received by each aliquot ranges between 3. The maximal bleaching is attempted after an exposure of around hours. The maximal bleaching percentage Bl. The annual dose rate is calculated from the radionu- clides activities obtained by gamma-ray spectrometry measurements. Alpha and beta attenuations in quartz Fig. Optical bleaching curves of the ESR Al-center for quartz extracted from fossil a and recent b sediments.
The maximal bleaching of the fossil sample is obtained after a hours exposure to the experimental device described in Voinchet et al. It corresponds to an equivalent six months exposure to the solar light. In the other hand, the Al-center of quartz issued from recent sediment is practically maximally bleached. It validates the hypothesis of initial optimal bleaching in natural conditions.
The cosmic dose depends on the altitude, latitude and on the sediment thickness above the sample Yokoyama et al, ESR dating of fluvial systems of northern France: Some results obtained during this study Voinchet, illustrate well the potential and the present limits of the ESR method and will be detailed now.
For each studied site, analytical data tables archaeological and annual doses, water content in sediment, maximal bleaching percentages and ages are presented on the respective illustrations. Dating of the lower terraces of the Yonne river system and of the palaeolithic sites of soucy The Yonne River is a tributary of the Seine River, which flows through the southern part of the Paris Basin in the Burgundy. Four sediments of the fine fluvial Soucy sequence and twelve horse teeth have been analysed fig.
These results are completed by further analyses realized on samples carried out from different localities of the same sheet, Gron and Michery.
For this last sample, a contamination of the sediment by material removed from an older alluvial deposit is suspected to explain the ancient age.
Respecting the geological evidences, the formation of the Soucy fluvial terrace is contemporaneous with the oceanic isotopic stage OIS 10 and these data places the human occupations during the OIS 9. In fact, the sensibility of the Al-center used for the dating seems to be too poor to allow a better discrimination of the alluvial formations younger than ka. Methodological works are still in progress to study the possible use of the ESR titanium-center, very much sensible than the Al-center, for the dating of such levels.
Results obtained on the creuse river system in the "Massif Central" sector The Creuse River is a tributary of the Loire catchment basin, in the central part of France, on the northern edge of the Massif Central and the southern and western parts of the Paris Basin. Recent researches have shown the impact of the recent tectonics and of the nature of the bedrock on the Pleistocene fluvial record. In the southern sector, located on the endogenous bedrock, several dam lakes mask the lowest part of the valley and only the higher alluvial outcrops have been observed.
The ESR geochronological studies were realized on sediments carried out from the different terraces. Results show a good reproducibility and generally a good coherence with the altimetry, except for the highest formation where two groups of age were obtained. ROSY software Brennan et al. Soil water content was The software's default values were used for the remaining parameters. Finding the dose rate to convert DA into an age is a crucial step after DA has been found.
ROSY software allows age to be calculated from an enamel sample by taking DA due to radioisotopes from adjacent layers into account. The software computes age based on three uranium absorption models linear, early uptake and a combination of both. Table 1 shows the soil analysis results. The present work did not determine U, Th and K concentration in enamel and dentine as their percentages have been negligible for calculating age in previous work, especially in dates for the Holocene period Kinoshita et al.
Typical soil density, enamel and dentine values were used for calculating age 2. Using these values and the radioisotope concentrations listed in Table 1ROSY software was used for obtaining the alpha, beta and gamma radiation dose rate contribution for each radioisotope in sediment the results are listed in Table 2.
These results were the same for any uranium absorption model. It should be noted that ROSY software calculates these ages using three uranium accumulation models: The way that uranium accumulates in a tooth is established by these models; accumulation increases at the same rate as time in the linear model and accumulation occurs in a short period of time in the early model, relative to a tooth's age and then remains constant after this short period of time. The tooth's age was the same when calculated by these three methods; this result was consistent if taken into account that the accumulation of radioactive elements inside the tooth was negligible.
Conclusions Age determined at many countries' archaeological sites is the result of radiocarbon 14C analysis of particular items found around the burials and not direct dating of individuals found there.
The results regarding either physical or geological phenomena may not be chronologically equal, hence the importance of having techniques like ESR which can directly and absolutely determine the age of individuals of interest.
This result agreed with stratigraphic analysis at sites providing soil ages ranging from 2, to 3,y BP for 50 and 80 cm depths Correal, ESR dating accuracy was obtained relatively straightforwardly, using just a few grams of tooth enamel, thereby highlighting some of the advantages and characteristics of the ESR dating method. The results so obtained have contributed towards joining links in the long chain of Colombian and American history where there is still much to do, due to the rich pre-Hispanic and colonial past.
This paper thus represents a pioneering effort aimed at promoting the dating of our ancestors. Rodriguez, for providing facilities and allowing the use of his samples, as well as AM Groot archaeologist for her support during this research. ESR dating of a toxodon tooth from a Brazilian karstic cave. Direct Dating of Human Fossils. Free Radicals in Biology and Medicine.
Electron spin resonance (ESR) dating of the origin of modern man.
Advances in ESR Applications. Use of electron paramagnetic resonance dosimetry with tooth enamel for retrospective dose assessment. Report of a coordinated research project. New applications of electron spin resonance: Concepts and Methods of ESR dating. ESR dosimetry of 89Sr- and Sm-in bone.
Electron spin resonance dating of human bones from Brazilian shell-mounds Sambaquis. Cosmic ray contributions to dose-rates for luminescense and ESR dating: Journal of Archaeological Science Chapters 1, 2, 3 and 4. The second international intercomparison on EPR tooth dosimetry.