Experimental maturation of pine resin in sediment to investigate the formation of synthetic copal and amber

Experimentally simulating fossil resin formation would improve our understanding of copal/amber and could simulate the diagenesis of resin inclusions. Resin from living Pinus underwent sediment-encased maturation under various temperature and pressure conditions. Light microscopy suggests that matured resin dries, possibly hardens, and darkens into a brittle, yellow-orange-brown translucent mass with increased luster, exhibiting flow lines, birefringence, conchoidal fracturing, and air pockets typical of copal/amber. Leached components were observed in the sediment. Infrared spectroscopy suggests that matured resins have spectra consistent with those of fossil resins and may exhibit similar differences from fresh resin-possibly decreased relative intensity of C=O stretching at ~ 1700 cm^-1. Results suggest desiccation and volatile/labile component loss, alongside potential polymerization/cross-linking of stable components into a macromolecule (although we discuss the challenge of 'Class V ambers'). 'Synthetic copal/amber' is amenable to destructive analyses and would guide studies of fossil resin inclusions in informed, predictable, and targeted manners to limit loss of rare specimens. With novel experimental methods involving fresh resin and utilizing sediment porosity, our work expands upon insights from commercial autoclaving of natural subfossil copal/fossil amber used to alter their physical properties. Considering the broad success of sediment-encased maturation to simulate carbonaceous compression fossils and ancient resins, we predict that experimental taphonomy will elucidate the fossilization potential of diverse plant biomolecules and even plant secondary metabolites related to herbivory, flavor, and pharmacology.