The aim of this study at the costal site of Kalba are investigations on lithic raw material procurement and usage. Especially during prehistoric times, copper and chert were important raw materials. The results of the material analyses offer considerable potential for investigating and assessing the significance and the use of geological resources of a prehistoric settlement.
Kalba – a trade centre on the Gulf of Oman
Around 5000 years ago, extended trading networks are evidenced for the first time, reaching from the eastern Mediterranean to the Indus region. During this period, the Early Bronze Age, numerous proto-urban settlements and trade centres emerged, situated on important geographical nodes of this trade network.
In the course of the successfully conducted project Across Arabia, it became clear that the coastal site of Kalba on the Gulf of Oman was an important node within the trade network of the 3rd millennium BC. This is evidenced by imported pottery from Mesopotamia, Iran and the Indus Region. The location of the settlement offered optimal conditions for the exchange of knowledge and goods between west and east, as well as north and south. Beside the favourable geographical location, the diachronic occupation – with hiata – from the Early Bronze Age to the Iron Age (c. 2500–600 BC) raises the question of whether there are other reasons for such a continuity. In this context chert (left) and copper (right) artefacts from the excavations at Kalba are of special interest. Due to the fact that sources of both materials are not located in the vicinity of the settlement, questions arise about the provenance of the artefacts or the raw materials and how these materials came to Kalba.
Regional to inter-regional raw material procurement? The potential of chert and copper analyses
Geologically, the vicinity of Kalba is influenced by the Semail Ophiolithe complex, situated in the west of the settlement, which resulted from an ocean-continent collision in the Late Cretaceous. As a result, the Al-Hadjar mountain range extends from Oman in the south to the United Arab Emirates in the north. Although it is known that copper deposits are located in the Al-Hadjar mountains, however, fundamental research is still lacking. A stroke of luck was the detection and investigation of the copper ore deposits with a copper smelting site (HLO1; cf. Fig. below) located in Wadi al Helo (Emirate of Sharjah), about 15 km (beeline) away from Kalba. Archaeological research at the site revealed that the copper ore deposits in Wadi al Helo were already known since the Early Bronze Age and copper was smelted on site. In particular HLO1 is of special significance due to the possibility that the copper acquired from the Al-Hadjar mountains was traded via the coastal site of Kalba. Thus, this could possibly be a motivation for the establishment of the settlement Kalba in this region in the 3rd millennium BC. In order to clarify this hypothesis, lead isotopy analyses of the copper ore and selected copper artefacts from the coastal site are mandatory.
In contrast to copper ore deposits, chert sources are not known from the immediate and wider environment of Kalba. Additionally, research on siliceous raw material sources used in prehistoric times is still lacking in the north of the United Arab Emirates. Investigations on potential sources of archaeological chert artefacts were only conducted in the course of the excavations at Jebel al-Buhais and Jebel al-Faya in the northeastern region of the Rub' al Khali desert. The survey revealed that sources are located in the western foothills of the Al-Hadjar mountains, approximately 50 km (beeline) from Kalba, beyond the mountains. However, detailed geological and geochemical analyses for the classification of the chert sources are outstanding. Therefore, a systematic sampling and analysis of the chert sources and the artefacts from Kalba are mandatory for revealing the provenance and, thus, assessing a possible procurement of chert from beyond the Al-Hadjar mountains. For this approach, in co-operation with the OREA Raw Material Lab the ›Multi Layered Chert Sourcing Approach‹ (MLA) method will be applied to enable an allocation of the artefacts and their sources.
The aim of analyses of artefacts from Kalba and raw material sources
The aim of the follow-up study at the costal sites of Kalba is investigations on lithic raw material procurement and usage. Especially during prehistoric times, copper and chert were important raw materials for the production of tools und adornments, whereby the material was sometimes traded over long distances. Thus, the copper ore deposits located nearby could have been a decisive reason to establish the settlement of Kalba as a trade centre on the coast of the Gulf of Oman. Another crucial factor is the existence of chert artefacts at Kalba. If the raw material was procured from the sources in the northwestern Rub' al Khali desert, Kalba could have functioned as a node between maritime trade networks and caravan routes leading to the inner part of the Arabian Peninsula. In this way, a much larger interaction sphere than currently presumed for the prehistoric times, reaching as far as the desert region, could be evidenced. Finally, the results of the material analyses offer considerable potential for investigating and assessing the significance and the use of geological resources of a prehistoric settlement.