Chemical characterization and provenance studies of archeological samples

Abstract

Data that is collected by chemical analyses of the archeological samples can be used to find out the the raw materials used and the techniques practiced in the ancient pottery production. In addition, provenance studies of archeological samples that are commercially important may give an idea on the commercial relationships between the past civilizations. This study was conducted to investigate the chemical compositions and provenance of the amphora samples that are found around Sinop and Heraclea Pontica (Black Sea Coast) in Turkey, Ibn-Hani (Eastern Mediterranean Coast) in Syria, Tanais and Gorgippia on Northern Black Sea region of Russia. Some amphorae, which are morphologically similar to those of Colchian amphorae, but having apparently distinctive clay properties, are called Pseudo-Colchian, and they were also analyzed during the studies. The mineral compositions of the samples were found out by powder X-Ray Diffraction analyses, and the elemental compositions were sought by X-Ray Fluorescence spectroscopy. Principal component analysis and cluster analysis are applied to the data collected from XRF measurements for the provenance classification of the samples. The results obtained from both statistical methods complemented each others and were in good agreement. According to the results of this study, the pink clay, red clay and white clay amphorae from Sinop are all found to be composed of the minerals quartz, feldspars, pyroxenes, calcite and hematite, but varying in amounts with respect to type and color. Considering the mineralogical compositions, it is proposed that the average baking temperature of the red clay amphorae is around 800 – 850 o C whereas it is around 950 o C for the white clay ones. The red color observed for the red clay Sinopean amphorae was attributed to the presence of hematite minerals. On the other hand white color was attributed to the formation of mineral phases such as pyroxenes, throughout the chemical reactions that take place in the clay matrix at higher baking tempertures and low oxidation environments for the white clay Sinopean amphorae.

In provenance classification of the samples, it was found that the separations between the samples occur mainly due to variations in the concentration of elements Ca, Fe, Ti, Ni, Rb and Sr. White clay amphorae from Antioch and Ibn Hani, and the red clay carrot type amphora from Tanais are found to be the Sinopean production. On the other hand, the white clay amphorae from Tanais was found to be more similar to the ones from Heraclea Pontica and different from those of Sinop. The colchian amphorae from Gorgippia and Pseudo-Colchian amphorae were found to represent typical differences from all other samples, but also from each others.