پژوهشی در کوپال و کاربرد آن در سواحل شمالی خلیج‌فارس نمونۀ مطالعاتی: کوپال‌های مکشوفه از محوطه‌های باستانی دیلم، گناوه و دیر (استان بوشهر)

Abstract
In this article, an effort is made to identify the actual functions of copal and to establish its approximate chronology while addressing the range of proposed functional interpretations. In addition, the spatial distribution of this cultural material within the study area and its corresponding distribution map are presented. The geographical scope of this research includes the historical sites of Dilam and Ganaveh counties in western Bushehr Province, as well as the more eastern localities of the province, such as the historical port of Najiram, the Bardo site (Bardestan), and the recently identified Konari fire temple (Kaki) in Deir city. The present study is based on library research and systematic archaeological investigations conducted along the northern shores of the Persian Gulf in Bushehr Province. As a result of this research, in addition to introducing the various types of copal and their distribution, examples dating from the Sassanid through the Islamic periods are examined, and their practical functions, including use as platform (bench) foundations around fire temples, local fire pits, and architectural elements, are discussed. The principal research questions concern the distribution range, production location, typological variation, function, and chronology of copal. Based on the research hypotheses, both the distribution area and production location of copal are situated along the shores of the Persian Gulf. Copal exhibits considerable variation in form and dimensions, indicating a diversity of functional applications. Among the documented uses of copal are its role as a decorative architectural element, as the base of domestic or local fire pits, and as the foundation of platforms (benches) surrounding fire pits within fire temples. From a chronological perspective, copal dates to the Sassanid period and the early centuries following Islam, with continued use extending into the middle Islamic periods.
Keywords: Persian Gulf, Copal, Sasanian Period, Islamic Period.
 
Introduction
Throughout history the Persian Gulf has functioned as the trade artery connecting East and West and as a focal point for cultural and commercial exchange in antiquity. The northern shores of the Persian Gulf provided favorable conditions for the establishment and prosperity of historic ports because of their distinctive natural features and coastal setting. Archaeological survey along these northern shores has identified sites spanning prehistoric, historical, and Islamic periods. Among recovered cultural materials, a distinct clay and stone object conventionally termed ‘copal’ demands attention. Although numerous copal examples have been recorded at northern Persian Gulf sites, no thorough and systematic study has yet been undertaken. The present research aims to establish the chronology of copal while examining its spatial distribution and morphological diversity and proposing refined functional interpretations. This study combines library research with targeted archaeological surveys and identification. First, data from published archaeological reports and other sources were collated. Then, findings from the author’s archaeological investigations along the northern Persian Gulf coasts in Bushehr Province — including western localities (Dilam and Ganaveh) and eastern localities (Deir) — carried out over the past two decades were assessed. Particular attention was given to contextual associations, stratigraphic occurrence, and evidence indicative of local manufacture or in-situ use. The study also evaluates associated ceramic assemblages and stratigraphic indicators to support chronological assignments and functional interpretations. 
Research questions: 1- What is the distribution range of copal and where was it produced? 2- What typological classes of copal exist and what were their functions? 3- To which historical period(s) does copal belong? 
Research assumptions: 1- Copal is restricted to the northern shores of the Persian Gulf and pertains to this archaeological region. 2- Copal dates to the Sassanid period but continued to be used architecturally from the early Islamic centuries. 3- Copal exhibits substantial variation in material and form, indicating diversity in production and use. and regional evidence also.
 
Discussion
The results of the conducted studies indicate that the highest concentration of copal is located in the western parts of Bushehr Province, particularly in the cities of Dilam and Ganaveh, followed by the more eastern areas of the province, including the historical ports of Najiram, Berdo, Siraf, and nearby offshore zones. During the archaeological survey and identification programme carried out in Ganaveh in the summer of 2013, a total of 37 sites containing remains of terracotta copals were documented. Among the sites yielding copal, one site contained prehistoric, historical, and Islamic materials, seven sites were attributed to the Sassanid period, and twenty-nine sites produced cultural materials dating to the onset of Islam or the early centuries following Islam. Copals recovered from seven sites associated with the Sassanid period and the early Islamic centuries were recorded either intact or thermally deformed, a condition suggesting local production of this cultural material at these locations. With regard to chronology, based on the analysis of pottery collected from the surface of these sites, the examined copals can be attributed to the Sassanid period through the early centuries after Islam. On copals from eighteen locations, traces and residues of plaster and sediment were observed, indicating the probable use of these objects as architectural elements.
In the archaeological survey of Dilam conducted in the winter of 2013, remains of complete or fragmented copals were identified at thirty-two ancient sites. Among these, six sites date to the Sassanid period, seventeen sites to the early Islamic centuries, and eight sites to the middle Islamic period. At the historic port of Najiram, situated ten kilometres west of Deir port, two terracotta copal specimens were identified that differ from the Ganaveh and Dilam examples in terms of size and morphological characteristics.
In illicit excavations at an area known as Chartaghi Castle, located four kilometers southeast of Kaki city and eleven kilometers northwest of Konari village in the Bardkhon district of Deir city, two terracotta copals are visible as platform foundations within the disturbed archaeological deposits. The paired copals, positioned one meter apart from one another, measure 56 cm in length, with two bands 44 cm long and 8 cm high at the upper end and 40 cm long and 8 cm wide at the base.
 
Conclusion
The analysis of copals recovered from the ports of Ganaveh and Dilam demonstrates that these objects date from the Sassanid period to the middle centuries following Islam (ninth century AH). Furthermore, the identification of copal remains deformed by intense furnace heat in nine locations suggests the local production of these copals along the northern coasts of the Persian Gulf. Among the recorded examples, more than twenty copals preserve traces of plaster and sediment, indicating their probable use as architectural elements. Copal remains were documented and examined at three key sites in Deir city. A substantial number of stone copals were identified at the ancient site of Bardistan. Based on the recognition of comparable examples within the Konari fire temple, it is possible to propose the use of copals as platform or bench foundations within fire temple architecture in the Persian Gulf region. In the historic port of Najiram, two terracotta copal specimens were recorded that differ from the Ganaveh and Dilam examples and were likely employed as architectural elements. In the central area of the fire temple, the remains of a platform (bench) constructed around the fire pit are visible. This platform consists of two supports and a single slab placed upon them. The foundations of this platform comprise two terracotta copals positioned beneath the stone slab. A copal specimen identified at Tell Sabz, Bandar Deir, differs in form from other examples. This copal is fashioned from black stone, fully polished, with a smooth basal surface and a plate-like upper surface bearing a short rim. A pronounced ridge is present on the body of the copal, and the two bands above and below it are executed with exceptional precision and quality.