FTIR spectroscopic features of the pteridosperm Ruflorinia orlandoi and host rock (Springhill Formation, Lower Cretaceous, Argentina)

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

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020

0895-9811

Rufloriniaorlandoi(Pteridospermophyta) fronds are chemically analyzed for the first time by semi-quantitativeFourier transform infrared (FTIR) spectroscopy. This analysis allows the chemical characterization of the me-sophyll and cuticle revealing the functional groups preserved in different frond parts (pinnae and rachis). Thespecimens collected in the Springhill Formation at the Río Correntoso locality (Lower Cretaceous, Santa Cruzprovince, Argentina) are compressions with very well-preserved cuticular features. TheR. orlandoiremains(pinnae and rachis) are spectroscopically analyzed into two samples: compressions (Cp) and cuticles (Ct).Additionally, a third sample form from the host rock and named associated coal (V) is spectroscopically ana-lyzed. Semi-quantitative data derived from Cp, Ct, and V spectra are evaluated by principal component analysis.The results indicate that Cp samples have a similar chemical composition whereas Ct samples show a greatervariability. The latter could be related to intraspecific variability of foliar characters (e.g., trichomes and cuti-cular striations). Furthermore, Ct samples exhibit high contents of aromatic carbon groups suggesting a dis-tinctive composition, likely including cutin/cutan biomacropolymers and/or phenolic compounds. Consideringeach specimen, the rachis shows a higher aromatic carbon content than pinnae as a consequence of the presenceof more lignified tissues in the former. The V samples have the lowest relative intensity of aliphatic groups. Onthe other hand, the functional-group composition ofR. orlandoiremains and V samples are compared withkerogen types and coal macerals showing a general chemical composition similar to type II kerogen. The latter isrelated to cuticles, spores, pollen grains, and resins.