Biomarkers in fossil resins and their palaeoecological significance

Fossil resins are the one of several fossil tree products, together with leaves, wood, seeds, or pollen. As an emanation of organic matter, resins are made of organic compounds, predominantly terpenes. Terpenes are broadly identified from various living organisms such as higher plants, fungi, or bacteria. In fossil resins, these compounds occur in several forms – usually mono-, sesqui-, di-, and tri-terpenes. Some terpenes present in fossil resins provide information about their ancestors and the paleoenvironmental conditions during the resin expulsion. These compounds, known as biomarkers, preserve the original shapes of molecules or occur as altered structures. Due to the chromatographic methods, insight into the chemical structure of fossil resins is enabled and biomarkers might be detected. In this study, information about the state-of-the-art chromatographic research concerning fossil resins was gathered. The biomarkers found in fossil resins were divided into compounds providing chemotaxonomic (botanical biomarkers) and environmental information (other biomarkers). Botanical biomarkers provide high utility in paleobotanical studies. The initial identification of a source tree, gymnosperm, or angiosperm is possible, due to certain chemical patterns of these types. Moreover, in chemotaxonomic studies, the restriction to more specific taxonomic levels, especially to the level of family, is usually possible, thanks to the occurrence of specific biomarkers. Many terpenes that are known to have an ecological function in extant plants are also found in fossil resins; however, their presence does not clearly indicate the ecological properties of trees due to the advanced alterations of the chemical structure. However, some specific environmental biomarkers found in fossil resins (e.g. succinic acid or rosane) might provide information about the paleoenvironment during the resin deposition.