Thermoluminescence (TL) dating and multivariate statistical methods based on radioisotope Xray fluorescence analysis have been utilized to date and classify Syrian archaeological ceramics fragment from Tel Jamous site. 54 samples were analyzed by radioisotope Xray fluorescence; 51 of them come from Tel Jamous archaeological site in Sahel Akkar region, Syria, which fairly represent ceramics belonging to the Middle Bronze Age (2150 to 1600 B.C.) and the remaining three samples come from MarTakla archaeological site fairly representative of the Byzantine ceramics. We have selected four fragments from Tel Jamous site to determinate their age using thermoluminescence (TL) method; the results revealed that the date assigned by archaeologists was good. An annular ^{109}Cd radioactive source was used to irradiate the samples in order to determine their chemical composition and the results were treated statistically using two methods, cluster and factor analysis. This treatment revealed two main groups; the first one contains only the three samples M52, M53, and M54 from MarTakla site, and the second one contains samples that belong to Tel Jamous site (local).
Analysis of archaeological ceramics can confirm the information recorded in historical documents, such as trade routes linking populations of different areas, and help to find out the chronology of events. Establishing databases of Syrian ceramics, by using many techniques, was started a few years ago.
The classification of ceramics based on typology is one of useful methods, but only when applied to whole or reconstructed objects [
To reach this goal many techniques were applied, since the initial ceramics study by Sayre and Dodson [
In the present study we applied
thermoluminescence (TL) dating for the age determination of ceramics sherds. This technique is the only available today to determine the age of ceramics. See [
radioisotope Xray fluorescence spectroscopy for determining the elemental composition of the ceramics, where fourteen chemical elements were determined.
XRF is nondestructive methods and allows fast multielemental analysis.
Fiftyfour samples were analyzed in this study. Fiftyone of them labeled 1–51 come from the excavation at the site of Tel Jamous in Sahel Akkar region located at the west of Syria (see Figure
Map of Syria with the area considered.
Four samples (samples JA, JB, JC, and JD) were chosen randomly among the 51 samples from Tel Jamous site, to be analyzed by thermoluminescence for age determination.
The data which consisted of the concentration of fourteen chemical elements have been treated statistically using two methods, cluster and factor analysis, to establish a categorization of the ceramics raw material source from Tel Jamous archaeological site. The chemical groups are assumed to present sources which could present the use of local material or production workshops.
The fine grain technique [
The next step is to obtain a quantity of powder, about 250 mg, through the drill within the sample; after that we added acetone, about 60 cm^{3}, to the sample and waited for 2 min. We left the precipitant and took the solution. We added acetone again and waited for 20 min. In the next step, we took this time the precipitant with a small amount of acetone. We put, using micropipette, 3 mL of the solution in each of the glass tubes (1 cm of diameter and 6 cm of height). Finally we leave the tubes for the next day in an oven at 50°C. The separated grains then are allowed to deposit on aluminum discs in a thin layer of a few microns thickness which are placed at the bottom of individual flatbottomed glass tubes. We prepared twenty discs for each sample, the whole discs were placed on the tray, using tweezers [
The age of the ceramics can be calculated by the absorbed dose or Paleodose (ED) in Gy unit divided by the dose rate (DR) in mGy/a or in Gy/ka. The absorbed dose, which is called equivalent dose (ED), is related to the time in which the samples are exposed to natural radiation, and the dose rate is the dose received from natural radiation by the sample for one year (annual dose). The measurements were performed using RISØ TL/OSL reader model DA20 at atomic energy commission of Syria. The additive dose procedure was used to determine the absorbed dose [
The sherds were ground, after removal of the surface deposit, using an agate mortar; this step is important to have good homogeneity of the analyzed sherds. The obtained powders were dried at 105°C for 24 hours; after that the powders were converted into pellets with a hydraulic press [
The pellets (25 mm diameter) were irradiated for 1000 sec. live time by an annular
The final data which consist of observations (samples) and variables (elements) have been treated using two statistical methods, cluster analysis (CA) and factor analysis (FA), by using Statistica 8.0 package. Cluster analysis (CA) classifies samples into distinct groups by calculating distance measures between the samples [
Using factor analysis (FA) we can extract a minimum number of factors which explains an acceptable amount of total variance of the data set. In general the two or three first factors are sufficient to reach this goal.
A growth curve was built on the basis of four additive beta doses using three discs for each dose. The graphs of additive dose versus luminescence counts were plotted. They are shown in Figure
U, Th, and K concentrations with internal annual dose, external annual dose, annual dose, equivalent doses, and the ages obtained and ages assigned by archaeologists for the pottery sherds investigated.
Sample  Internal dose 
External dose 
Annual dose 
Archaeodose (Gy)  Age (a) B.P  Age assigned by archaeologists 

JA 





1600–2150 B.C. 
JB 





1600–2150 B.C. 
JC 





1600–2150 B.C. 
jD 





1600–2150 B.C. 
The dose rate conversion factors used are given in Adamiec and Aitken [
Luminescence counts versus additive dose for the four samples JA, JB, JC, and JD.
JA
JB
JC
JD
Alpha rays have the shortest range in geological materials (approximately 0.03 mm); beta rays traverse up to 3 mm in solid matter, while gamma rays penetrate about 30 cm, much greater than the dimensions of our pottery samples.
Before TL measurements are carried out on our sherds, the outer 3 mm of the sample is cut away. The remaining portion has therefore received its alpha and beta dose entirely from within the volume of the sherd. This dose, termed the internal dose, can be determined from an examination of the sample alone. Like the alpha and beta rays, gamma radiation derives from the decay of naturally occurring radionuclides present in the ground, such as potassium40 and members of the uranium and thorium decay series.
The doses rates (annual doses) are presented in Table
We can notice from Table
The statistical analysis was performed after elimination of the elements in the data set which have more than 25% missing values and then transform the data to base log.10. Only 12 elements were considered for the statistical analysis. The elements Cu and Ni were not included because their concentrations values are missing for more than 50% of samples analyzed.
The two elements niobium and lead have three and four missing values, respectively. The procedure used to estimate the missing values for them was to replace any missing value by the minimum detection limits (MDL) determined by XRF. The MDL are 15 ppm (niobium) and 10 ppm (lead). The final data set consisted of 54 observations (samples) and 12 variables (elements) for a total of 648 data entries.
The resulting dendrogram based on the analysis of 12 elements is shown in Figure
Grouping of pottery samples by cluster analysis.
The factor analysis (FA) was carried out on the same twelve elements used for cluster analysis. The three factors extracted in this study explain 63.8% of the total variance of the data set. Varimax method was used for rotation and maximum likelihood method was used for factor extraction.
Table
Factor loading for the samples data set, twelve elements.
Elements  Factor 1  Factor 2  Factor 3 

Ca  −0.31  0.84  −0.25 
Fe  0.32  0.29  0.52 
K  −0.10  0.91  0.02 
Mn  0.31  0.04  0.72 
Nb  0.25  −0.77  −0.22 
Pb  0.04  −0.64  −0.31 
Rb  0.35  −0.20  0.51 
Sr  −0.51  0.34  −0.09 
Ti  0.81  −0.19  0.34 
Y  0.94  −0.25  0.03 
Zn  0.47  0.27  0.39 
Zr  0.70  −0.15  0.38 


Total variance %  25.0  24.8  14.0 
Factor score 1 against factor score 2 of ceramics samples.
Factor score 1 against factor score 3 of ceramics samples.
The results confirm, after statistical analysis using two methods, that there are one principal group which contains 48 samples derived from Tel Jamous site and another group which contains “control” samples, that is, samples M51, M52, and M53, derived from MarTakla site. The 48 samples of category 2 are thus considered to correspond to wares manufactured in Tel Jamous site.
Finally Table
Mean values and standard deviation for the two chemical groups in the pottery. All values are in
Elements  Group 1 ( 
Group 2 ( 

Ca 


Cu 


Fe 


K 


Mn 


Nb 


Ni 


Pb 


Rb 


Sr 


Ti 


Y 


Zn 


Zr 


Thermoluminescence (TL) dating and Xray fluorescence (XRF) analysis combined with multivariate statistical method have been utilized to analyze 51 ceramics samples from Tel Jamous site, Syria. Four samples among them were chosen for dating. Three additional ceramics samples from MarTakla archaeological site were used as “control” samples. The ceramics sherds of Tel Jamous date back to the Middle Bronze Age (2150 to 1600 B.C.) according to archaeologists. The date obtained by TL technique was in good agreement with the date assigned by archaeologists. Up to 14 elements were determined by XRF and the concentrations of 12 of them have been taken into consideration for statistical analysis where two methods were applied, cluster analysis and factor analysis, in order to classify the ceramic sherds. Statistical results separate samples 2, 9, and 20, put samples M52, M53, and M54 from MarTakla archaeological site in an isolated group, and confirm that there is one principal group of ceramics from Tel Jamous site. Application of XRF, TL techniques, and statistical analysis has proved to be very helpful for Syrian archaeologists to study ancient ceramics. This study could be beneficial in geological studies such as sediment studies where optically stimulated luminescence (OSL) technique is used in general instead of TL technique for chronological dating t of the sediments.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors wish to thank the International Atomic Energy Agency (RAS/1/011) and the General Director of AEC of Syria for their support of this work and the General Director of antiquity and museum in Damascus for supplying the samples discussed in this study.