IAEA Progress Report II

Contract number: 13266/Regular Budget Fund (RBF)

Title of Project: “Study of archeological objects using PIXE analytical technique”.

Institute: National Council for Scientific Research, Lebanese Atomic Energy Commission.

Chief Scientific Investigator: Mohamad Roumié

Time period: April 2006- May 2007

1- Introduction

After adopting the PIXE one-run measurement using the Al funny filter as X-ray absorber which was described in the first progress report, two studies on ceramics were undertaken in order to be characterized based on their chemical composition. The first one concerned the characterization of 38 sherds from the locality of Ch'him (south of ) that could help for future studies on ceramic provenance. Those samples are considered as reference materials as they are coming from kiln and workshop of the excavated site. The second study will be detailed in the current report. It concerned excavated pottery from Beirut, suspected to belong to North-Syrian production.

2- Archeological context

The Anglo-Lebanese excavations in downtown Beirut (1994-1996: Sites BEY 006, 007 and 045) have yielded an archaeological sequence of deposits from the 5th century BC to the Medieval period. The pottery selected here for analysis is a representative sample of the wide range of coastal Syrian products that were imported during the Hellenistic to Byzantine periods (late 3rd BC to 5th century AD) for their contents (amphorae) as well as for their special functional roles (large basins, mortars and braziers). For the first time they have been identified as being of likely coastal north- Syrian origin. Both Ras al Basit and Amrit are likely to be the principal sources of these products. The complex range of amphora forms and ‘variants’ suggests that other, possibly coastal, centers were also involved in amphora exports. The clays of some Byzantine amphorae could indicate their origin near but not at Ras al Basit. Some products in clays rich in fossil shell could indicate varied origins in the orbit of Amrit, but equally also in northern Lebanon (e.g. ). At this stage we can only sample a range of likely ‘Amrit’, ‘Ras al Basit’ and ‘Batroun’ products to see if they group into three sets and compare how the other products sampled correspond to them. The study of exported Syrian products found in Beirut will provide key evidence for the roles in trade of the various postulated centers in northern , as well as northern Lebanon.

3- Target preparation The selected ceramics were chosen from pre-groups already established according to archeological-typological criteria. The surface layers of the sherds were removed, as they are more liable to present alterations in their composition due to chemical exchanges with the surrounding soil. Samples were heated for one hour at 950˚C, and then left to cool down in the oven. After crushing into an agate mortar, the collected powder was pressed into pellets with a hydraulic press. The grain size is less than 20 m, which was far smaller than the beam size (~2 mm), and hence a better homogeneity of the analyzed sample is achieved. In order to avoid a charge build-up at the surface during the analysis, the sample was covered, using an adapted carbon deposition evaporator, by a very thin ultra pure Carbon layer (<10 g/cm2).

3- Results The use of the Al pinhole filter provided 28 trace and major elements in one spectrum: Na, Mg, Al, Si, P, S, Cl, Ca, K, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Ba, W and Pb. However, only 12 elements were chosen for cluster analysis as follows: MgO, Al2O3, SiO2, K2O, CaO, TiO2, Fe2O3, Ni, Zn, Rb, Zr and Sr. The different PIXE spectra were processed with the Gupix package (Guelph PIXE software package). Then, cluster analysis was performed, using a multivariate statistical program, to group together objects that have similar elemental compositions. It used the Gupix data matrix, containing the sample identification as columns and the chemical elements or characteristics as rows. The data was standardized before clustering, to make all characteristics contribute equally to the discrimination process, using Euclidean distance as the distance measure and unweighted pair-group average as the linkage rule. Consequently, the hierarchical cluster analysis, of the 46 collected ceramic objects that are representative of the excavated materials, showed the main compositional groups with some marginal samples (Fig. 1) with their elemental characteristics (Table 1). Group 1, consisting of a large group of samples and comprising several sub-groups, suggests that all are closer to ‘Amrit’ in character than to Ras-al-Basit, perhaps because of their higher fossil shell and lower volcanic content, while the other group is constituted mainly from

Ras-al-basit reference samples. This group has high concentrations of CaO, TiO2, Zr, Sr and Rb, while Al2O3, SiO2 and MgO are quite low (Table 1). The Amrit amphora, including the two complete type pieces on display in the Museum of (lib130 and lib131) and a fair number of other examples found in Beirut, has spread throughout this large ‘Amrit’ group. The different obtained results will serve as well for the already established database related to the elemental composition.

Fig. 1: Classification of the studied ceramics, including mostly examples found in Beirut, as well as examples from Ras-al-basit and Amrit (see symbols chart). The hierarchical cluster analysis was applied to standardized concentrations of 12 chemical elements. The main resulting groups are underlined.

Group 1 (n = 30) Group 2 (n = 5) m σ m σ CaO 37.29 9.53 4.98 2.37 Fe2O3 8.43 1.38 9.45 0.70 TiO2 1.26 0.22 0.37 0.12 K2O 0.86 0.28 0.67 0.18 SiO2 38.66 6.88 53.31 0.77 Al2O3 10.69 1.88 25.64 2.24 MgO 1.78 0.64 4.29 0.72 MnO 0.13 0.07 0.11 0.01 Zr 219 94 25 12 Sr 997 472 146 41 Rb 45 13 24 9 Zn 113 33 52 7 Table 1: Average of elemental concentrations m and standard deviations σ for the resulted main groups shown in the dendrogram of figure 3: group 1 for Amrit (from lib130 to lib154) and group 2 for Ras-al- basit fabrics (from lib161 to lib166). The compositions are in percentage for the oxides CaO to MnO and in ppm for trace elements Zr to Zn.