FTIR spectroscopy studies in Cretaceous gymnosperms from the Santa Cruz province, Patagonia, Argentina

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

INTERNATIONAL JOURNAL OF PLANT SCIENCES

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 2021 p. 508 - 522

1058-5893

Premise ofthe Research. In this contribution, the spectroscopiccharacterization of Gymnosperms fossil remains belonging to Pteridospermophyta,Cycadophyta, Ginkgophyta, and Coniferophyta collected from the Anfiteatro deTicó and Punta del Barco formations (Baqueró Group; Aptian) and Springhill (Hauterivian-Barremian) and PiedraClavada/Kachaike (Albian) formations, outcropping in the Santa Cruz province,Argentina is presented. From these lithostratigraphic units, specimens ofseveral fossil taxa showing the existence of a diverse plant assemblage duringthe Lower Cretaceous in Patagonia were selected. Methodology. The fossilsconsist of foliar compressions with very well-preserved cuticles that arechemically characterized by Fourier Transform Infrared (FTIR) spectroscopy.Foliar remains are analyzed into two sample forms: 1) compressions (including coalifiedmesophyll and cuticle; Cp) and 2) cuticles (Ct). Additionally, semiquantitativedata are evaluated through Principal Component Analysis (PCA) revealing thefunctional groups preserved at the mesophyll and cuticle levels for each analyzedfossil taxa. PivotalResults. In general, the species from the Baqueró Group show similar chemicalcompositions between the Cp and Ct sample forms whereas the chemistry of thefoliar compressions from the Springhill and Piedra Clavada/Kachaike formationsreveals the presence of a high contribution of aromatic structures making upthe cuticles.Conclusions. Thecompressions of Pseudoctenis ornata, Ginkgoites tigrensis, and Squamastrobustigrensis probably underwent, during and after diagenesis, a naturaloxidation process most likely caused by the recurrent volcanic activityoccurred during the Aptian sedimentation of the Baqueró Group. In contrast, Rufloriniaorlandoi, Ptilophyllum micropapillosum, and Ginkgoitesskottsbergii have cuticles presumably composed of highlyaromatic structures (such as phenylpropanoids and aromatic domains) in cutinsand cutans as well due to the presence ofother phenolic compounds. A new term is here proposedfor Ginkgoites skottsbergii: vitrinitic compression,while Pseudoctenis ornata,Ginkgoites tigrensis, Squamastrobus tigrensis, Ptilophyllummicropapillosum, and Ruflorinia orlandoi are called liptiniticcompressions.