Amphora production in the Guadalquivir valley (Spain) during the Late Roman period: petrographic, mineralogical, and chemical characterization of reference groups

Abstract

This paper presents a scientific analysis of Late Roman amphorae from four kiln sites located in the Guadalquivir river basin: Azanaque-Castillejo (AZ), Isla de la Barqueta (IB), Las Monjas-Soto del Rey (SR), and Picachos (PIC). This region was a significant producer and exporter of oil in the Roman Empire and also during the Late Roman period. The amphorae analyzed belong to type Dressel 23 and were used for trading oil to other Mediterranean regions. A total of 36 amphora samples were analyzed by using a combination of instrumental analytical techniques, including thin-section optical microscopy, X-ray diffraction, and X-ray fluorescence, in order to establish reference groups based on the petrographic, mineralogical, and chemical characterization of the materials. The amphorae from the four kiln sites showed approximately similar petrographic fabrics and chemical compositions, as well as strong technological similarities. However, there are slight petrographic and/or chemical differences that allowed for the differentiation of three reference groups (AZ, SR, and IB-PIC). These groups were also compared with existing reference groups for Early Roman amphorae in the same area, and compositional differences were also observed. This is the first time that compositional reference groups for Late Roman amphora kiln sites in the Guadalquivir valley are characterized. Hence, the results of this research not only contribute new evidence on the study of oil amphora production in this region, but they will also serve as a basis for the identification and sourcing of these amphorae in consumption sites and, consequently, for a better understanding of trade networks during the Late Roman period.