Late Roman cooking pottery from the Tavoliere area (Southern Italy): raw materials and technological aspects

摘要

This study describes the results of petrographical, mineralogical and chemical analyses carried out on coarse tempered cooking pottery, sampled in the archaeological sites of , Posta Crusta (Ordona, FG) and San Giusto (Lucera, FG). From the latter site, two fragments of a pottery kiln, coeval with sherds (IV and V centuries AD), were also investigated. Two groups of clayey sediments of different nature (alluvial and marine) sampled in the neighbouring of the archaeological sites were also analysed. By means of the petrographical analyses, all cooking pottery and the two kiln fragments were grouped in the same coarse tempered group, characterised by the scarce presence of trachytic and glassy fragments, anhedral and zoned augitic pyroxenes and feldspars. PXRD analyses show an abundant presence of quartz and feldspars, followed by pyroxenes and variable quantities of calcite and hematite. Among clay minerals, illite plus muscovite are more abundant than smectite. XRF analyses data display SiO₂, Al₂O₃, Fe₂O₃ and K₂O as main oxides, with variable quantities of CaO. In the case of the clayey samples, petrographical investigations on thin-section of psammitic fractions outlined the differences between (Marine group—Pleistocene) and the alluvial deposits of Celone River (Alluvial group—Holocene). The occurrence of volcanic products, chert, garnet, quartzarenites and limestones in the archaeological materials and in the alluvial samples, let us suppose that cooking pottery was made with alluvial clayey silt. The apparent chemical discordance between pottery and alluvial samples bulk compositions can be due to textural and compositional variability of the alluvial deposits. All ceramics were fired in oxidising conditions, although in many cases a "dark core" was still present. Textural features, observed through petrographical microscope, and PXRD analyses suggested a firing temperature between 600 and 800 °C.