Ceramic Pottery Production in the North Caucasus in the Bronze Age and the Iron Age

The ceramic pottery production in the North Caucasus in the Bronze and Iron Age enables us to understand the production technology, technological development and transfer, craft system and mobility of the potters in the semi-sedentary and semi-mobile society. However, most prehistoric archaeological ceramics are heterogeneous composite materials containing various chemical and mineralogical compositions, firing states and alteration degrees, so that the ceramic production technology cannot be easily characterized and classified. Moreover, the amount of the excavated ceramic objects is huge, which causes additional difficulty for the analysis. In order to overcome these limitations, multiproxy- and multiscale-approach was employed step by step using polarization light microscopy (PM), scanning electron microscopy with energy/wavelength-dispersive spectroscopy (SEM/SEM-EDS/WDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), synchrotron radiation Fourier transform infrared (SR-FTIR), Raman spectroscopy, three dimensional micro computed tomography (3D µ-CT) and image analysis. Firing conditions such as time, heating rate and temperature were concretized by the kinetics of the dehydroxylation of the clay mineral and finite different method (FDM) on the oxygen diffusion and heat transfer. This combined approach focused on resource gathering, firing and shaping techniques. The total 150 samples excavated at two archaeological sites in the North Caucasus, Ransyrt 1 (Middle/Late Bronze Age) and Kabardinka 2 (Late Bronze/Early Iron Age) were investigated. Samples of 21 ceramic sherds uncovered at Levinsadovka and Saf’janovo around the Sea of Azov, Russia (Late/Final Bronze Age) were compared to the mountain ceramics. According to the results, the mineralogy and shape parameters of sand grains and chemical composition of the ceramic matrix composed of grains smaller than 50 µm were able to distinguish the ceramic pastes from each site. This provides the potters’ practice of the main use of the local resource. The alignment of the large pore complex and grains enabled to identify the continuous or modular slab building by hands for the formation of the ceramic pottery body. The firing techniques were derived from the pyrometamorphic process under oxidizing and reducing conditions and corresponding firing behavior of the composite materials containing the common clay mineral, cis/trans-vacant (cv/tv) 1M illite. The complex combination of clay sintering, pore topology and its Euler characteristic and transformation of the indicator minerals such as calcite, hematite, spinel and gehlenite gave detailed clues for the firing temperature thresholds between under 675 and 1200 °C. In many ceramics fired in the oxidizing atmosphere, the reactivity between oxygen and Fe-, C- and S-bearing phases present in the ceramic pastes caused localization of the redox state within a sample, forming a color profile on the cross section of the object. In the middle of the cross section of those samples, earlier dehydroxylation of illite and corresponding total collapse occur due to the local reduction. The firing conditions derived from the dehydroxylation kinetics of illite and simulation of the oxygen diffusion and heat transfer indicate that the non-isothermal conditions with the high heating rate could produce the ceramic pottery with various firing degrees within a few hours by the instant firing without a furnace. The firing practice at both sites were similar, however the firing temperatures of the Kabardinka 2 ceramics are distributed in the wider range than those of the Ransyrt 1 ones, which might be related to the longer history of the settlement at Kabardinka 2. According to the combination of the archaeometric results and archaeological contexts, the local ceramic pottery production technologies at both sites were driven by similar human practice and site-specific resource. Although the individual decision making in the pottery production contributed to the heterogeneity of the ceramics as well, the resource-driven local technological styles dominated the pottery production at the studied sites in the Bronze and Iron Age. This characterization will shed light on the understanding of the development and transfer of the production technology in the North Caucasus