Their similarity with other buildings such as Ivry-la-Bataille castle or London Tower required determining the place of Avranches keep in this group: Therefore, samples of brick for luminescence dating were taken from the remaining little tower.
Results indicate a chronology later than assumed: These dates tend to prove that north-east tower remains would correspond to a reconstruction phase and not to the original construction.
"Thermoluminescence dating aitken pdf merge" keep of Avranches is one of the case studies of this group. Archeomagnetism and thermoluminescence were performed in this study in order to date the last firing of the ceramic materials such as the bricks.
This crossing of approaches constitutes an asset for this period for which the question of reused material is systematically raised. In this paper, the luminescence dating results are described and integrated in the interpretation of the history of the building.
It faces the Mont-Saint-Michel bay and its location gives to the town a strategic defensive position. The town is divided in two parts: The keep is located at the junction of these parts, in the most vulnerable area of the city. Two centers are present in the old town: Its reconstructed plan leaded to indisputable form comparisons with the emblematic Anglo-Norman keeps such as the Ivry-la-Bataille one, that of the Tower of London fig.
Whether its edification is one of the first examples of early Anglo-Norman keeps or the result of a continuity of castle building during a war period needs to be ascertained. A previous passageway through this load-bearing wall, turned into a niche, is built with Thermoluminescence dating aitken pdf merge for the arch and Thermoluminescence dating aitken pdf merge jambs.
Furthermore in the extension of the load-bearing wall, north orientated, i. In order to determine the chronology of the use and the making of these bricks, five brick Thermoluminescence dating aitken pdf merge were taken from the two architecturally distinct masonry units mentioned. This was in view of checking the assumption of an anteriority of the Avranches keep on other emblematic which take parts of the large corpus of Anglo-Norman C11 th th keeps.
A fifth sample was taken from the south wall of the previous passageway turned into a niche facing the arch where came the four first samples BDX from. In spite of the little number of samples available due to the limited area of welle preserved remains, 5 samples are enough to get a sufficiently accurate age of this structure.
Thermoluminescence dating aitken pdf merge However, the dates that are to be obtained are only representative of this little part of the whole castle building.
We recall that it allows dating the last firing of minerals of items, such as bricks. The age is given by the following
Thermoluminescence dating aitken pdf merge. To measure the time elapsed since the last firing two series of experimentation are performed: These experimental stages are preceded by stage of characterization of the material in order to evaluate the most suitable dating protocol.
Furthermore possible irradiation heterogeneities are studied, such as those due to the presence of radioactive spots zircons, monazites, for the most usual species in the ceramic matrix, even included in quartz crystals used in the luminescence Blain et al.
In addition, checking the homogeneity of a series of samples may reinforce the idea of contemporaneity of the brickmaking. The five bricks show different clay colors which vary from red to dark brown.
It can be noticed that the bricks show different grain size characteristics, with white or grey plurimillimetric sized inclusions. A number of blue and mauve inclusions are visible on the five bricks; they could be K-feldspars and quartz respectively.
The two bricks BDX and BDX have associations of inclusions of different nature which correspond to K-feldspars and calcosodic feldspars imbricated with quartz crystals, remains of granite rock fragments, in agreement with a possible local origin of the raw material.
These inclusions could also entail a dosimetric obstacle for the study in thermoluminescence difficulties to calculate the internal dose rate of the grains"Thermoluminescence dating aitken pdf merge" as they are all plurimillimetric inclusions more than 5 mm diameter they will be removed for the dating process.
The differences noticed in the composition in major contents of the bricks are comparable with the radiochemical composition fig. Moreover, the variability of composition of the bricks could be interpreted as a possibility of material reuse or a non-uniform chronology of the bricks, what was checked by luminescence dating.
After gently crushing the ceramics, quartz are extracted following a three-step process:. H 2 O 2 treatment for two weeks to dissolve the organic material 50 vol. After each cycle, an "Thermoluminescence dating aitken pdf merge" of the material is performed by cathodoluminescence on small aliquots, in order to monitor the progress of the acid etching and the purity of the quartz powder obtained.
The experimental parameters are the following: The first one consists of reading the thermoluminescence of a first set of aliquots, with or without doses added to the natural dose. A second step consists of measuring the thermoluminescence of another set of aliquots previously annealed and irradiated in the laboratory with doses surrounding the irradiations used in the first step.
A growth law of thermoluminescence versus added dose is deduced from the experimental data of the second step which is applied to the experimental data of the first step Guibert et al. By comparing the signal related to the natural dose of the non-annealed material to the signal produced by doses given in the laboratory, the most suitable annealing temperature is determined best resemblance between the regenerated TL after annealing and natural TL.
For the k value, a standard value of 0. The g and cosmic environmental contributions are determined by "Thermoluminescence dating aitken pdf merge" situ dosimetry and gammametry. Dosimeters are CaSO 4: Tm powder in brass containers which are left Thermoluminescence dating aitken pdf merge months on the site. Field gammametry is measured with a portable g spectrometer NaI: K, U and Th contents are converted into a and b doses Adamiec et Aitken, Thermoluminescence dating aitken pdf merge concentrations given in table 3 show that contents in K and Th are similar between brick samples fig.
On the opposite, the U content is significantly more variable, as a possible consequence of the diversity of the raw material. Three values of the equivalent uranium content are determined from the gamma spectra:. Paleodose measured associated to their statistical uncertainty and annealing temperature used befor the regeneration of the TL signal. We consider that kind of disequilibrium is inherited from the raw material, initially in disequilibrium.
In addition, with two samples, Pb is significantly lower than Ra. According to these interpretations, we consider the annual dose as constant since the firing of the bricks, and we will neglect the possible changes of gamma dose-rate due to the modifications of the surrounding masonries. This latter assumption is supported by the examination of sections of bricks that do not exhibit any radioactive inclusion trapped in the quartz grains, unlike what we observed Thermoluminescence dating aitken pdf merge bricks of other medieval sites of the Armorican Massif Thermoluminescence dating aitken pdf merge Guibert et al.
As the etching of the brick powder Thermoluminescence dating aitken pdf merge more or less intact the outer parts of the quartz grains, we took account of the alpha contribution, supposing a k-factor of 0. The effective alpha annual dose is then given by the product of the transmission factor by the alpha k-factor and by the energy released by U and Th series alpha particles coming from the baked earth matrix.
Within these subclasses of grains, the grain-size distributions are supposed to be constant. Table4 reports the values that were used in this work and gives an example of a dose transmission factor determination from sample Bdx To these dates are associated uncertainties of two types.
Firstly the systematic uncertainties affect equally the dates calibration of the high resolution gamma-spectrometry, of the radioactive sources used…. Secondly, random uncertainties are taken into account; they are random errors on independent measurements amongst them, the uncertainties due to the counting in gamma spectrometry, the uncertainties due to discrepancy of the TL curves used in the paleodose.
The dates are substantially homogeneous, whether for the samples from the arch or that from the wall. "Thermoluminescence dating aitken pdf merge" of the annual dose and its global value; uncertainties given at one standard deviation, take into account statistical and systematic errors. This choice, taking four samples into account instead of five, can be explained by the fact that "Thermoluminescence dating aitken pdf merge" four samples belong to the same architectural unit, i. Indeed, besides the absence of written records related to this topic, the examination of the building shows no evidence of fire.
Alpha and beta transmission factors according to the grain size. The experimental mass distribution of quartz grains of the sample Bdx is given as an example of the way of determination of the mean dose rate transmission factor and corresponding standard deviation.
The hypothesis of a reconstruction or redevelopment phase can then be suggested. Bythe king of France Thermoluminescence dating aitken pdf merge Auguste regains the crown of England to the duchy of Normandy as well as all the other continental territories. These circumstances could have been favourable to the reconstruction, partial or total, of the keep of Avranches under the aegis of the royal power. Dates are presented after water content correction. In this case, we may consider that the builders of this construction chose the use of a material omnipresent in the building in order to preserve the harmony.
However it would be interesting to search for other bricks which presence is confirmed in 19 th century iconographic sources, and preserved in the lowest parts of the north wall of the keep currently hidden by a superimposed retaining wall.
Ancient TL 16 2: Ancient TL, 14 2: G uibert Thermoluminescence dating aitken pdf merge, P. Research leading habilitation, University of Bordeaux 3. Radiation Measurements44, Editions Picard, 2 tomes. A sampling strategy adapted to the keep of Avranches, a controversial building. Luminescence and radioactivity data. Archaeological interpretations of the archeometric data. A sampling strategy adapted to the keep of Avranches, a controversial building 3 The site of
Thermoluminescence dating aitken pdf merge stands m above sea level, on a granite massif.
Agrandir Original jpeg,
Thermoluminescence dating aitken pdf merge. Agrandir Original jpeg, k. Agrandir Original png, 89k.
Agrandir Original png, 48k. Agrandir Original png, 39k. Agrandir Original png, 71k. Agrandir Original png, 53k. Agrandir Original png, 43k.
Table des illustrations Titre Figure 1: Dater, une histoire qui date! Presses universitaires de Rennes Support: The paper deals Thermoluminescence dating aitken pdf merge the thermoluminescence (TL) dating of ancient Egyptian pottery taken from a site in the Giza pyramids. effective values which were estimated using the Aitken. that induced in the same sample by a subsequent irradi.
This "zeroing" is the basis for thermoluminescence dating of ceramics (which are average age of several samples from the same archaeological context is used.
. Aitken, M.J., and "Thermoluminescence dating aitken pdf merge," J.C.,The Assessment of Error Limits in. method of dating pottery was applied to samples of Chichen Itza, Yucatan, Chichen Itza, pottery, volcanic glass, thermoluminescence dating, fine. confidence level (Aitken, ). at the same dose,), 1ß= Gy, 2 = Gy, 3ß= Gy.