A03_P03

TAR PRODUCTION IN THE MEDIEVAL BOHEMIA TRACKED THROUGH GAS CHROMATOGRAPHY AND RADIOCARBON DATING

Brychova V¹, Krofta T², Svetlik I¹, Pachnerova Brabcova K¹, Petrova M¹

¹Czech Radiocarbon Laboratory, Department of Radiation Dosimetry, Nuclear Physics Institute CAS, Prague, Czech Republic, ²Department of Information Sources and Landscape Archaeology, Institute of Archaeology of the CAS Prague, Prague, Czech Republic

Accurate dating of tar kilns is crucial not only for understanding economic history but also for historical anthropology and environmental history. The historical production of tar in Bohemia is one of the neglected topics, although tar was an indispensable substance with a wide range of applications, and evidence of its production in Bohemia is dated back to the Neolithic. Dry distillation of coniferous wood leads to different types of products. A liquid organic phase, tar, is rich in diterpenic compounds, mostly retene, abietic acid and its derivatives. From the analysis of several archaeological pottery and soil samples, it is known these compounds can survive in a depositional environment over a long time scale. In this study, we sampled charcoal, pottery, and charred resinous residue from a supposedly medieval tar kiln in Brdy mountains (Central Bohemian region). Samples of pottery and resinous surface residues were subjected to solvent extraction and gas chromatography analysis to scan organic compounds preserved. Samples of charcoal and charred residue were radiocarbon dated. Pottery and charred residues solvent extracts differed in organic compound composition and concentration. Pottery extracts were dominated by long and very long fatty acids with a contribution of diterpenic residues - retene and abietic acid derivatives. Radiocarbon dates of charcoals fall into 12th century AD. Radiocarbon dating of pottery extract or surface residue through a more compound-specific approach is under further study.