Archaeometric Study of Potteries Excavated from Deh Dumen Archaeological Site (Southwestern Iran) Preliminary Results

Technical and analytical studies on archaeological and cultural materials is one of the interesting subjects of the modern archaeological research studies leading to consideration of scientists to find new information about the old technologies and material culture. One of the important cultural and archaeological materials considered by the material scientists and archaeological science scholars are ceramics, especially pottery production in the different periods. In this paper, potteries excavated from the Deh Dumen Bronze Age graveyard (Third millennium BC) located at southwestern Iran were studied by using chemical and petrographic analytical techniques, with the aim to characterize their chemical composition and microstructure and to identify the pottery manufacturing process in this region. For this purpose, twenty-four samples from broken pottery vases were selected among those obtained from the different graves of the site, and were analyzed by X-ray fluorescence (XRF) and polarized optical microscopy (POM) methods. The results of XRF analysis showed that the samples can be classified in two main groups: Ca-rich (or calcareous) and Ca-poor (or non-calcareous) potteries. Furthermore, Al₂O₃ and Fe₂O₃ were detected as the main components of samples. On the other hand, the pottery samples present two different structure types: bright and sandwich-like structures. POM examination of the potteries revealed a fine-grained clay matrix with quartz and feldspars fragments as temper. Numerous small and large particles of calcite grains as well as clay pellets are scattered in the matrix of the potteries. Based on these results, it is proved that a large part of the potteries of the Deh Dumen site had been produced by a local and simple pottery manufacturing technique that led to the formation of sandwich-like structure and contained large and small calcitic and clayey inclusions in a large number of potteries. On the other hand, potteries with different microstructures might have been imported form neighbor regions.
  
Introduction
The history of pottery production in the Iranian Plateau goes back to about 10000 years ago and shows the importance of this craft in the development of technology within this region during the prehistoric time. The study of potteries as most found materials in the archaeological excavations has been an interesting subject for archaeologists and scientists, as it enables identifying ancient technology in the old world. Nevertheless, even if some study has been performed on archaeological potteries excavated in Iran, it is necessary to develop analytical studies to better characterize the pottery production in this region. The Bronze Age graveyard of Deh Dumen is located in southwestern Iran on mountain slopes about 100 m south-west of Deh Dumen village, a suburb of Dena Township, and about 70 km north-west of the city of Yasuj, the capital of Kohgiluyeh and Boyer-Ahmad province. In the 2013’s archaeological excavations, a 20 × 30 m trench was excavated, revealing 15 large graves built with stones. Many objects were placed in the graves close to skeletons. They included different styles of pottery, also different metallic artefacts such as vessels and weapons, as well as stone vessels and arrowheads. Most of the potteries from the graves have a red to brown slipped fabric and includes jars with impressed decorative bands on the body and base, as well as jars with parallel grooved and jagged decorations on the body. The pottery styles of the Deh Dumen are similar to the Bronze Age of Luristan as well as Susa D. To characterize procedure of production in the Deh Dumen potteries, an analytical study including chemical and microstructural analyses was carried out. Twenty-four samples were selected from the broken vases including 8 samples with bright yellow fabric and 16 samples with different fabric including orange-red surface layer and black core. The chemical composition of samples was determined by means of X-ray fluorescence (XRF) by using a PANalytical PERL’X 3 X-ray analyzer. In addition, to determine the petrography of potteries, a thin section was prepared from each sample and was observed by polarized optical microscopy method (POM) by using a Zeiss Primotech microscope. 
 
Identified Traces
Results of XRF analysis of potteries revealed that SiO₂ is the main component and CaO is a variable constituent in the composition of samples. In fact, the Deh Dumen potteries can be classified as calcareous (or Ca-rich) and non-calcareous (or Ca-poor). Al₂O₃ and Fe₂O₃ are other main constituents in the composition of potteries. The analyzed samples show similar chemical composition, with different contents in CaO, which can be considered as the only variable constituent in the Deh Dumen potteries. There is no correlation between CaO amount and the appearance classification of the samples (bright or sandwich-like core), Ca-rich potteries are observed in yellow and sandwich-like pottery groups. Microstructure of samples presents a very fine-grained clayey matrix in which fine particles of quartz and feldspars are scattered. On the other hand, small and large particles of calcite (limestone particles) with sharp edges are visible in the microstructure of samples showing that they have been added to pottery paste deliberately, probably by powdering the local limestone and use the powder as filler. Furthermore, clay pellets are visible in the matrix of samples in different sizes. The calcitic and clayey inclusions are more visible in the bright (yellow) core group of potteries. In the second group (sandwich-like structure) it is visible that the matrix near the surface is orange-red in color while in inside of the samples is darker, and black in some cases. This could be due to presence of organic materials in the structure of potteries (such as plant as filler) and incomplete oxidation atmosphere in the kiln may have led to formation of sandwich-like or black core structure in more potteries of the Deh Dumen site. Finally, presence of unaltered, not decomposed, calcite and clay particles and the structure of samples suggest that the heating temperature of the potteries can be estimated lower than 800 °C.
 
Conclusion
Analytical studies on several potteries from the Bronze Age graveyard of Deh Dumen, southwestern Iran, showed that they were manufactured using a simple method, consisting in using local clayey materials with significant amount of quartz, limestone powder as well as plant as filler, heated in a kiln under an incomplete oxidizing atmosphere, which led to a sandwich-like structure. Of course, there are some potteries that are different to others, namely potteries with a yellow structure (bright) and a fine clayey matrix with small quartz and silicate phases scattered in the matrix. These samples have very small calcitic particles and inclusions and no evidence of sandwich-like structure is visible. Based on the analytical results, it can be concluded that the Deh Dumen potteries can be divided into locally produced and possibly imported objects, the latter group probably proceeding from southwestern Iran such as the Susiana plain. The results of this preliminary analytical study revealed some aspects of pottery production in southwestern Iran during the Bronze Age.