Fossil resins are essentially macromolecular mixtures of polymerised plant terpenes. Our approach rests on previous studies whereby low molecular weight, volatile hydrocarbons could be produced by heating a resin specimen under vacuum with the products analysed and characterised by classical GC-MS. The structures of these hydrocarbons could then be related to the precursor terpenoids and then to the plant group from which they were derived. Using this approach, we were recently able to show that amber which regularly washes up on South Australian and Victorian beaches originates in Southeast Asia.
We have since added a new dimension to this work by determination of the isotopic composition of resins in their bulk form as well as of individual compounds produced by pyrolysis. We have also perfored complementary isotopic analyses on resins from extant plant groups from known habitats. Our preliminary results suggest that "Class I" resinites derived from gymnosperms are systematically enriched in the heavy carbon isotope compared with the angiosperm-derived "Class II" resinites. Interestingly, while there is a wealth of comparative literature data on the isotopic compositions of leaves, wood, flowers and other plant tissues, there is virtually nothing known about resins themselves. Thus we have been filling this gap by conducting a systematic study of the isotopic relationships between resin and some other plant tissues for a suite of extant angiosperms and gymnosperms. Simultaneously, we have been conducting isotope analyses of specific resin-derived hydrocarbons from petroleum in order to learn more about the plant communities that were the source of this fossil organic matter.