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

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

Salvador

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

Universidade Estadual de Feira de Santana

Chemical preservation states of Mesozoic gymnosperms leaves(Santa Cruz and Mendoza, Argentina). A chemometric approachMaiten A. Lafuente Diaz1, José A. D?Angelo2, 3, Georgina M. Del Fueyo11 División Paleobotánica, Museo Argentino de Ciencias Naturales, ?Bernardino Rivadavia? - MACN-CONICET, Av. Ángel Gallardo470, 1405 Buenos Aires, Argentina, maitenlafuentediaz@gmail.com.2 IANIGLA-CCT-CONICET-MENDOZA. Área de Química, FCEN, Universidad Nacional de Cuyo, M5502JMA, Mendoza, Argentina3 Palaeobotanical Laboratory, Cape Breton University, Sydney, Nova Scotia B1P 6L2, CanadaThe cuticle has numerous functions of essential importance for plant life and provides a broad set of information,including many biochemical investigations in both fossil and extant gymnosperms and angiosperms. Inthis contribution, two gymnosperm fossil taxa were chemically compared using semi-quantitative Fouriertransform infrared (FTIR) spectroscopy. These derived IR-data were then interpreted by principal componentanalysis (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 ofArgentina 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 dataas a function of functional groups(chemical structures), which are related to a variety of preserved features in both taxa cuticles. Furthermore,Squamastrobus tigrensis and Jonhstonia coriacea fossil plants do not completely conform to any of the threemost commonly known, general states of coalified-preserved plant fossils that are mainly defined according tochemical criteria; i.e., compressions, fossilized cuticles, and cuticle-free coalified layers. Results also indicatethat a number of different physico-geochemical conditions proceeding along a multidimensional continuum,resulted in different preservations states which can occur in nature. In fact, specimens of S. tigrensis andJ. coriacea can be considered as in-between stages of the wide spectrum of organic matter transformations.It is a contribution to grants ANPCyTPICT 2012/528 and CONICET PIP 112-201201-00212.Keywords: spectrochemistry, preservation, compressions, Cretaceous, Triassic.