Mollusc shells as a tool for seasonality reconstructions in the HAS1 settlement (Holocene, Oman)

Mollusc shells are a common component of many archaeological assemblages, as they occur in quite all the environments which were either occupied or exploited by humans in the past. These shells have a significant and growing potential for reconstructing palaeoenvironments, palaeoclimates and human-environment interactions. The HAS1 settlement (Iron Age and Classical Period) in the Khor Rhori Archaeological Park in the Dhofar region, southern Oman, show rich mollusc assemblages, present both in circular structures within the settlement and in a shell midden nearby. Here, we analysed through a high resolution sclerochemical approach (δ18O, δ13C) ten mollusc specimens belonging to three different bivalve and gastropod species (Anadara uropigimelana, Tivela stefaninii and Oliva bulbosa) coming from five different stratigraphic units of the HAS1 site after having checked their shell preservation with Scanning Electron Microscope and X-ray Diffraction. The aim of this study is to reconstruct the palaeoclimate and the seasonality variation recorded by mollusc shells during the human occupation and to investigate if the different analysed species record in the same way climate oscillations, being thus good biomineral archives for past reconstructions in archaeological settings. Different climatic factors acted and are still active nowadays in the Dhofar region, namely monsoon and coastal upwelling, which complicate the interpretation of the stable isotope signals recorded by the shells. Notwithstanding this, mollusc shells from the HAS1 site seem to record an increasing trend in seasonality through the analysed time interval, possibly linked to an intensification of monsoon and upwelling activities in southern Oman during the Iron Age and Classical Period.