Review and Source Identification of the Obsidian Tools of Ali Kosh Tepe, Dehloran Plain

Obsidian is one of the volcanic rocks that can be turned into glass as it cools rapidly. The remarkably high sharpness of the edges of the tools made from these rocks has led it to attract the attraction of pre-historic people quickly. The limited resources of this rock in the Near East and the Caucasus have made it possible for researchers to identify the chemical characteristics of each source for provenance purposes. The first sign of the obsidian exchange in the Near East dates back to the New Paleolithic period and in the Shannidar Cave in Iraqi Kurdistan, and has continued up to the end of the Chalcolithic period. The geological structure of Iran and the possible availability of such sources in Iran, as well as the reports on the existence of tools with unknown sources, strengthened the idea of obsidian sources in Iran. Previous results showed that all specimens of Tapeh Ali Kosh belong to unknown sources; and the previous report in this regard may be false due to the fact that no complete database of all available sources were known, since such researches have been in their inchoate stages. Based on the data obtained, Tapeh Ali Kosh was actually the most important site in the southwest of Iran during the Neolithic period and was the basis of Ilam chronology. A total of 347 obsidian fragments (9% of the total stone tools) were found in Tapeh Ali Kosh and in Buz Mordeh phases. In the Ali Kosh phase, 2% of the tools belong to obsidian instruments (474 pieces). However, in the Buz Mordeh phase, a decline in the proportion of tools was observed. At this stage, the number of obsidian instruments equals to 417 pieces, which includes 1.7% of the tools. Some of the researchers of obsidians in Iran, since the beginning of this kind of studies, due to the few reports about the samples of unknown sources and also to the volcanic structure of different regions of Iran, have always investigated the obsidian sources which are inside Iran. While, Tapeh Ali Kosh in Deh Luran plain is one of the most important sites, which is one of the first studied archaeological sites on obsidian provenance. Among the samples obtained from this site, some specimens from unknown sources have been reported. The main questions of this study were: 1- If more examples be analyzed, new sources could be identified? 2- Considering the identification of various sources and new subsources in the Caucasus, Asia Minor, Afghanistan, and the Arabian Peninsula, samples from this new source are among the Tapeh Ali Kosh tools? 3- Because of extensive studies have been carried out on obsidian sources and subsources in different regions; are there any samples from Tapeh Ali Kosh with unknown source? In this research, some specimens were selected to evaluate such ideas and theories after more than 50 years. Twenty one obsidian artifacts were collected from Tapeh Ali Kosh for the study. All specimens were surface finds and include blades, flakes, and debitage ranging in size from 2 to 4 cm. All 21 samples were sent to the Archaeometry Laboratory at the University of Missouri Research Reactor (MURR) for analysis by X-ray fluorescence (pXRF). A Bruker III-V portable spectrometer was used for the pXRF analysis. Twelve elements (including K, Ti, Mn, Fe, Zn, Ga, Rb, Sr, Y, Zr, Nb, and Th) could be measured in each sample, but only six of these (Fe, Rb, Sr, Y, Zr, and Nb) are useful for provenance of the obsidian artifacts. The results showed that two specimens were from Nemrut/Bingol (specimens no. 3 and 13), and 4 specimens were from Meydan Dag, i.e. specimens no. 6, 9, 10, and 16. The remaining 15 specimens belong to Nemrut Dag B. Based on the results obtained, it is known that the specimens found at Tapeh Ali Kosh have been supplied from at least two, and at most three sources, and from one unknown source. While in other study conducted on Chogha Ahowan and Chia Sabz specimens, no unknown specimens have been reported.