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 MARTIN A.

INTERNATIONAL JOURNAL OF PLANT SCIENCES

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 2020

1058-5893

Premise of the Research. In this contribution, the spectroscopic characterization ofGymnosperms fossil remains belonging to Pteridospermophyta, Cycadophyta,Ginkgophyta, and Coniferophyta collected from the Anfiteatro de Ticó and Punta delBarco formations (Baqueró Group; Aptian) and Springhill (Hauterivian-Barremian) andPiedra Clavada/Kachaike (Albian) formations, outcropping in the Santa Cruz province,Argentina is presented. From these lithostratigraphic units, specimens of several fossiltaxa showing the existence of a diverse plant assemblage during the LowerCretaceous in Patagonia were selected.Methodology. The fossils consist of foliar compressions with very well-preservedcuticles that are chemically characterized by Fourier Transform Infrared (FTIR)spectroscopy. Foliar remains are analyzed into two sample forms: 1) compressions(including coalified mesophyll and cuticle; Cp) and 2) cuticles (Ct). Additionally,semiquantitative data are evaluated through Principal Component Analysis (PCA)revealing the functional groups preserved at the mesophyll and cuticle levels for eachanalyzed fossil taxa.Pivotal Results. In general, the species from the Baqueró Group show similar chemicalcompositions between the Cp and Ct sample forms whereas the chemistry of the foliarcompressions from the Springhill and Piedra Clavada/Kachaike formations reveals thepresence of a high contribution of aromatic structures making up the cuticles.Conclusions. The compressions of Pseudoctenis ornata , Ginkgoites tigrensis , andSquamastrobus tigrensis probably underwent, during and after diagenesis, a naturaloxidation process most likely caused by the recurrent volcanic activity occurred duringthe Aptian sedimentation of the Baqueró Group. In contrast, Ruflorinia orlandoi ,Ptilophyllum micropapillosum , and Ginkgoites skottsbergii have cuticles presumablycomposed of highly aromatic structures (such as phenylpropanoids and aromaticdomains) in cutins and cutans as well due to the presence of other phenoliccompounds. A new term is here proposed for Ginkgoites skottsbergii : vitriniticcompression, while P seudoctenis ornata , Ginkgoites tigrensis, Squamastrobustigrensis, Ptilophyllum micropapillosum , and Ruflorinia orlandoi are called liptiniticcompressions.