PRESERVED CHEMISTRY OF PTILOPHYLLUM FRONDS FROM THE SPRINGHILL FORMATION (LOWER CRETACEOUS, ARGENTINA)

LAFUENTE DIAZ, MAITEN A.; CARRIZO, MARTÍN A; DEL FUEYO, GEORGINA M.; D'ANGELO, JOSÉ A.

Otro; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2018

Fronds of a new species of Ptilophyllum Harris (Bennettitales) are analyzed for the first time by semi- quantitative Fourier Transform Infrared (FTIR) spectroscopy with the aim of revealing mesophyll and cuticle chemical structures (functional groups) preserved in different frond parts (apical, medium, basal) as well as their relation with kerogen types. Fossils are compressions with well- preserved cuticles (MPM-PB 15355) found in the Springhill Formation (Hauterivian- Barremian) at the Río Correntoso Locality, Santa Cruz. For the spectrometric study, fronds parts were analyzed into two sample forms: (1) compressions (including coalified mesophyll and cuticle) and (2) cuticles. Semi- quantitative IR- data were evaluated using PCA showing the behavior of the analyzed categories according to the functional groups. In order to distinguish the existence of differences depending on the frond parts an ANOVA was carried out using the two first PCs data. The results indicate that compressions have a similar chemical composition while cuticles show a greater variability. In the first case, the mesophyll may hide cuticular differences between samples. In the second case, the variation mainly reflected on oxygen- containing compounds may be due to the cuticle chemical composition and its transformation through the fossilization process. Also, the cuticle samples show a higher aromatic carbon contribution than the compressions. The latter can be related to the cuticle biopolymer and its monomers. Additionally, no difference was detected by ANOVAanalysis depending on the frond zone for both sample forms. Furthermore, the sample forms have a general chemical composition similar to Type IIkerogenrelated to cuticles, spores, and resins.