مطالعه‌ی باستان‌سنجی سفال‌های گورستان عصر مفرغی کِشیک شهرستان نیکشهر

Accidental discovery of pre-historic site of Keshik in Nikshahr city of Sistan and Baluchistan, SE IRAN revealed a third millennium BC. Bronze Age cemetery which contains noteworthy artifacts like metal, pottery and etc. this study focuses on the characterization of potteries findings in the Keshik ancient site. Archeaometric studies were carried out on fragments of very important jar called Life Cycle Jar and 9 other pieces of potteries which were obtained from rescue archaeological excavation by Heidari in the Keshik cemetery during 2010. All samples were tested using Interdisciplinary laboratory analysis methods similar to petrography and x-ray diffraction analysis with powder method and the techniques of construction, the differences and structural similarities, and the type of mineral to obtain the origin of their deposits were studied. Due to the uniformity of the existed mineral elements in the soil, the results of the above methods indicate the use of soils with alluvial and regional origin of the Keshik River for all potters, which indicate the local origin of the pottery studied in the area. Also, no variety of minerals is observed in the making pottery, and all of them follow the consistency characteristics of mineralogy and technology. Pottery tufts manufacturing technology is evident in cross sections due to the same alignment of cavities. Regarding the presence of calcite minerals in potteries 4, 5 and 10, temperatures of up to 850 °C and for other potteries beyond that can be suggested. Finally, according to the analyzes carried out, all selected samples represent the same and similar structural elements and minerals in the study area and as a result of the indigenous nature of the production of ceramics. The conducted analyzes present the similarity of all samples, both in terms of the materials used in the fabrication and the technique and the manufacturing method.
Keywords: Archaeometry, Petrography, XRPD, Keshik Cemetery, South East of Iran’s.
 
Introduction
During the accidental discovery of Keshik cemetery of Nikshahr city and its life-saving excavations in 2012 by Mohammad Heydari, noteworthy artifacts were discovered and identified from the Bronze Age of Baluchistan region. Among which the most important are bronze works, such as beads, container pieces, daggers, and various stone works as well as pottery wares (brick red, beige and simple gray-colored containers as bowls, cups, goblet, and various types of vats and stoup in different sizes). This ancient site, which includes several cemeteries, areas and architecture, is one of the most significant settlement sites of the Bronze Age until the early centuries of the second millennium BC and it is located along the west-east communication highway of the Iranian plateau and south-east of Hamun-e Jaz Murian (Heydari, 2012). In the meantime, the discovered data related to the pottery wares of this cemetery is of particular importance in the regional studies of the Southeast. Because these pottery wares represent the regional and even trans-regional relevance of the Bronze Age residents of Keshik with their surrounding regions and cultures. The designs and themes on these works have particular similarities to the designs on other sites pottery works in the area, such as Spidej, Bampur and so on. But among the pottery works discovered in Keshik cemetery in addition to tall engraved glasses, discovering a relatively large pottery vat with a brick-reddish beige color and unique designs is really important. On this vat, that due to its themes is called “the vat of life”, the scenes of a goat are depicted from mating, giving birth to the baby (goat), breastfeeding and reaching adulthood. Due to the technical and artistic characteristics of the pottery works discovered in the Keshik area, it was necessary that these works be examined in terms of archaeometry studies. Cultural materials and pyro technological products, including ceramics, are one of the best materials in archaeometry and archaeological studies to study and understand the economies, livelihoods, and lives of ancient people. Ceramics have heterogeneous multiphase systems that require different methods of analysis and testing. The study of ancient pottery in archaeometry is mainly concerned with their structural and fuzzy studies (Romani et al, 2000), which this study has attempted to rely on. So, to achieve the objectives of this study, 10 pieces of these pottery works were studied.
 
Laboratory Analysis Methods
Microscopic Thin-Section Analysis
The specimens are all totally crystalline and fine and vary in thickness from 5 mm to 1 cm. The specimens are mostly in two colors (some three colors) in the cross-section and have light brown to gray and some of them are red-brown. There is no great variety of minerals in pottery works production. Quartz mineral exists in both single crystal and multi-crystal forms with iron oxide in all samples. The samples studied in this site have almost identical composition and a common origin. The texture of all samples is fine crystalline or silty. The main mineral in the samples is quartz, which is mainly crystalline and phenocryst and to a lesser extent polycrystalline. The other components that can be seen in most samples are the Greg pieces that a limited amount is found in the samples. In this sample, in addition to the quartz constituents, iron oxide and Greg pieces, calcite mineral is also found which is not present in the other samples.
 
X-Ray Powder Diffraction (XRPD) Analysis
Based on the XRPD analysis of the desired samples spectra, phases such as quartz, calcite, hematite, and plagioclase have been identified in all pottery. One of the most prominent identified phases in pottery works is quartz mineral, which has also been observed in thin sections of pottery works. Iron-bearing phases of hematite are other phases identified in all pottery. This phase is one of the phases of oxidation conditions in all of the identified pottery works. Calcite is one of the identified phases of samples 4 and 10, which can also be cited in microscopic studies. The identified graphite phase indicates the presence of carbon in the clay textures, and the light gray core observed at parts of the sections is a reason to identify this phase. This phase is due to carbon sequestration in the tissues and imbalance in the delivery of oxygen to pottery in the furnace and darkening their core.
 
Conclusion
Based on the conducted studies, it was found that these pottery wares have the same workmanship and identical origin in terms of geology and additives to context and production technology. Pottery wares all have circular quartz pieces indicating that they are alluvial in origin and are also uniformly spread in the texture of the ceramics and have a very good kneading in the initial preparation and processing of the matrix. This may be justified by the presence of the Keshik River in the region, which suggests that the potter may have used alluvial and sedimentary soils of the Keshik River for pottery works, but no certain idea can be indicated regarding this issue, because, soil used in the construction of pottery wares was washed, clean, and very sticky, so the pores in the pottery texture were very small. South and east parts of the area are rich in alluvial and sedimentary layers, perhaps these sedimentary materials were used to make the matrix of these pottery wares. Another possibility that can confirm the native origin of these pottery wares is the identification and discovery of furnaces and gray melted and glassilized pottery wares that are obtained during the studies of Gorgy and his colleagues. The XRPD analysis of the pottery wares also confirmed the structural and fuzzy similarities between the objects. But based on the themes found on the discovered pottery wares, it is possible to find out the connections between the people of Keshik and the people of other areas, such as Spidej, Bampur, Chegerdak, and even Shahr-i Sokhta. It is possible to divide the pottery into two types of with calcite grains and calcite-free pottery in the furnace. The lower firing temperature for specimens 4, 5 and 10 than 850 to 750 ° C is suggested (due to the presence of calcite in the tissue) and a higher temperature is suggested for other pottery wares.