CHEMICAL ANALYSES OF FOSSIL AND MODERN PLANT RESINS USING C-13 SSNMR

Fossilized plant resin, or amber, is notable in having exquisitely preserved organisms or parts of them. Additionally, some features of the biology of these organisms are traceable to the Lower Cretaceous (ca. 130 Ma). Resins, complex mixtures of carbon-rich molecules insoluble in water, have been produced by numerous ancestral vascular plants, including the Medullosales, since as early as the Middle Carboniferous (ca. 305 Ma). Of all plant exudates, including resins, latexes, and gums, distributed in over 485 genera and 144 plant families, it appears that only resins occur in geologic deposits. Nevertheless, the botanical source of many ancient resins remains obscure. As the chemical nature of resins may vary with plant species, the characterization of modern resins by different physicochemical techniques are used to establish the likely botanical origin of ancient resins. However, ancient resins are seldom associated with taxonomically diagnostic plant organs or tissues. C-13 SSNMR is a state-of-the-art research tool that generates spectra (or signatures) of solids. This technique is the only method that can distinguish the botanical sources of a wide variety of ancient and modern resins. Our analyses use a tiny amount of the solid resin (< 0.5 gram) and are non-destructive. Peaks in different regions of the spectra represent different kinds of chemical bonds, distinguished by their resonances, present in the sample. Data from these resins will be presented from four research areas of evolutionary paleobiology. First, the refinement of our knowledge of fossil and modern plant resins by generating a library of C-13 SSNMR chemical signatures for them. Second, from a chemical library of exudate samples, the identification and reconstruction of resiniferous forests can take into account varied plant species that may have been diachronous sources in the same general locality. Third, given the large number of modern resin samples at hand from closely-related plants, there is a basis for commenting on their classification. Fourth, more ancient resin samples may yield data useful to understand the evolution of plant resin types. These chemical approaches provide an alternative and complementary methodology for reconstructing resin-producing forests, particularly for lineages with extant representatives.