Chemical preservation states of mesozoic gymnosperms leaves (Santa Cruz and Mendoza, Argentina). A chemometric approach

LAFUENTE DIAZ, M; D`ANGELO J A; DEL FUEYO, G

Congreso; XIV International Palynological Congress - X International Organization of Palaeobotany Conference; 2016

The cuticle has numerous functions of essential importance for plant life that provides a broad array of studies, including many biochemical investigations in both fossil and extant gymnosperms and angiosperms. In this contribution, two gymnosperm fossil taxa were chemically compared using semi-quantitative Fourier transform infrared (FTIR) spectroscopy. These derived IR-data were then interpreted by principal component analysis (PCA) while a complementary anatomical study was performed using scanning electron microscopy (SEM). The material consists of very well preserved coalified gymnosperm leaves from the Mesozoic of Argentina belonging to Squamastrobus tigrensis Archangelsky & Del Fueyo (Coniferales, Lower Cretaceous, Santa Cruz) and to Jonhstonia coriacea Walkom (Corystospermales, Middle to Upper Triassic, Mendoza). The resulting multivariate model shows differences in grouping of data as a function of functional groups (chemical structures), which are related to variably preserved features of both taxa cuticles. Furthermore, Squamastrobus tigrensis and Jonhstonia coriacea fossil plants do not completely conform to any of the three most commonly known, general states of coalified-preserved plant fossils that are mainly defined according to chemical criteria; i.e., compressions, fossilized cuticles, and cuticle-free coalified layers. Results also indicate that a number of different physicogeochemical conditions proceeding along a multidimensional continuum, resulted in different preservations states which can occur in nature. In fact, specimens of S. tigrensis and J. coriacea can be considered as in-between stages of the wide spectrum of organic matter transformations. It is a contribution to grants ANPCyT PICT 2012/528 and CONICET PIP 112-201201-00212.