New Evidence on the Reliable Use of Stable Isotopes of Bitumen Fractions in Archaeological Research

• Published in: Molecules (Basel, Switzerland) Vol. 28; no. 4; p. 1962
• Main Authors: Pennetta, Antonio, De Benedetto, Giuseppe E
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.02.2023; MDPI
• Subjects: Absorption; Archaeological sites; Archaeology; asphaltene; Asphaltenes; Biomarkers; bitumen; Bitumens; Bituminous materials; Bronze Age; Carbon; Ceramics; EA-IRMS; Geology; Historic buildings & sites; Historic sites; Human populations; Hydrocarbons; Isotope ratios; Isotopes; lipid absorption; Lipids; Neolithic; Paleolithic; Pictographs; Populations; Pottery; Ratios; Resins; Stable isotopes; Italy; Albania; stable isotopes; lipid absorption; EA-IRMS; asphaltene; bitumen
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28041962

One of the goals of archaeological studies is to determine how material goods and ideas moved among human populations, and bitumen is a worthy proxy because it has been used since prehistory. As a result, when bitumen is excavated from archaeological sites, determining its provenance is important because it sheds light on the trade and communication of populations at a given time. During the study of archaeological bitumen from coastal sites in central and southern Puglia (Italy), we observed that stable isotope ratios of saturated and aromatic fractions were incompatible with those obtained from asphaltenes, supporting the absorption of a foreign substance. Experiments showed that lipids are absorbed by bitumen and, in the case of oils, are distributed mainly in the saturated and aromatic fractions as their isotopic ratios change. The same experiments showed that the isotopic ratios of the asphaltenes do not change. Lipid absorption on the archaeological bitumen may have occurred before the bitumen was applied to the pottery, during the use of the pottery or while underground, before being excavated. These hypotheses are discussed, and it is concluded that the isotopic ratio of asphaltenes is a reliable proxy for provenance, whereas those of the saturated and aromatic fractions should be considered with caution due to possible lipid absorption. Nevertheless, they provide new information on pottery use that can be used in archaeological chemistry.