Radioactive Isotope Ratios as a Novel Method of Ancient Pottery Analysis: Ostrowite Archaeological Site Data

Abstract

The radioactive isotope content of any geological sample (lithic rock, sand, silt or clay) is characteristic for a specific type of geological material. The use of the isotope ratio method allows each sample to be distinguished in terms of source. In this study the radioactive isotope ratio method has been applied to a set of ceramic pottery specimens from the same multi-layered archaeological site and probably produced from local raw material. The method shows the similarities within the ceramic material used to manufacture the pottery. The variations in the quantitative and qualitative compositions of the basic products (clay, silt, loam, sand, ash and organic admixtures) used in the preparation of the ceramic paste change the isotopic composition and activity ratios. Pottery from each ceramic manufacturing centre, based on the specific composition of the raw materials, have characteristic isotope ratios. Radioactive isotope ratios as fingerprints of ancient ceramic manufacturing centres have not yet been applied as an archaeometric method. The proposed method has been applied to a Striatemulti-phased settlement complex and pottery manufacturing centre in Ostrowite in northern Poland. The earliest pottery to be manufactured in Ostrowite dates to5200-5000 BC, during the existence of the Early Neolithic settlement. Subsequent settlement phases and pottery production horizons are dated to the early Iron Age (approx.800-600 BC), the Roman period (1st to 4th centuries AD) and the Middle Ages (11th to14th centuriesAD). The site has a long tradition and experience in ceramic production.In this study two isotope ratios were applied: 40K/ 228Ac and 226Ra/ 208Tl. The proposed non-destructive archaeometric method allows the analysis of vessel fragments. This study analysed 11 fragments of Neolithic pottery,3 fragments from the early Iron Age, 5fragments from the Roman period, 5 specimens from the medieval period, 3 burned clay samples and 8 raw material samples, all collected from the Ostrowite complex.This pilot study confirm the grouping of the isotope ratio results for each type of the samples, even in terms of similarities with the base clay material collected in this region.