Species-level determination of closely related araucarian resins using FTIR spectroscopy and its implications for the provenance of New Zealand amber

Abstract

Some higher plants, both angiosperms and gymnosperms, can produce resins and some of these resins can polymerize and fossilize to form ambers. Various physical and chemical techniques have been used to identify and profile different plant resins and have then been applied to fossilized resins (ambers), to try to detect their parent plant affinities and understand the process of polymerization, with varying levels of success. Here we focus on resins produced from today’s most resinous conifer family, the Araucariaceae, which are thought to be the parent plants of some of the Southern Hemisphere’s fossil resin deposits. Fourier transform infrared (FTIR) spectra of the resins of closely related Araucariaceae species were examined to test whether they could be distinguished at genus and species level and whether the results could then be used to infer the parent plant of a New Zealand amber. The resin FTIR spectra are distinguishable from each other, and the three Araucaria species sampled produced similar FTIR spectra, to which Wollemia resin is most similar. Interspecific variability of the FTIR spectra is greatest in the three Agathis species tested. The New Zealand amber sample is similar in key shared features with the resin samples, but it does differ from the extant resin samples in key distinguishing features, nonetheless it is most similar to the resin of Agathis australis in this dataset. However on comparison with previously published FTIR spectra of similar aged amber and older (Eocene) resinites both found in coals from New Zealand and fresh Agathis australis resin, our amber has some features that imply a relatively immature resin, which was not expected from an amber of the Miocene age.

Identification of the process of hydromechanical extraction of amber

“…To determine the magnitude of the coefficient  we will use the results of experimental studies by wellknown authors on the emergence of amber particles in laboratory and field conditions [19][20][21][22][23][24][25][26][27][28][29]. In this case, expression (11) will have a more convenient definition for  :…”

“…This means that in order to adequately describe the processes under consideration, it is necessary to take into account the change in not only the density but also the effective viscosity of the liquefied medium. Similar processes are realized in the processing of bulk material in vibrating, boiling and pulsating fluidized layers [12][13][14][15][16][17][18][19][20][21][22][23][24]. The results of the analysis of known mathematical models describing hydrodynamic processes in such layers with steady or pulsed air supply suggest two types of formulas for calculating the dynamic viscosity coefficient of the liquid medium under consideration [29].…”

Amber inclusions from New Zealand

“…(Evans, 1937;Lambert et al, 1993;Seyfullah et al, 2015). There is fossil evidence for other now locally (Seyfullah et al, 2015).…”

Results of experimental studies of amber extraction by hydromechanical method in Ukraine

“…Physical-chemical properties of amber allow selecting a method of extraction [3], however, the studies have a scope that is limited by the region of amber extraction. Molecular component has little impact on production, and explores the uniqueness of a valuable sedimentary [4].…”

“…Many researchers are interested in the physical and chemical properties of amber [3]. A characteristic feature of such studies is the research into molecular level [4].…”