Chemical preservation of Cretaceus gymnosperms leaves from the Baqueró Group (Aptian, Santa Cruz, Argentina)

DIAZ, MAITEN A. LAFUENTE; D`ANGELO J A; DEL FUEYO, GEORGINA M.; CARRIZO M A

Simposio; XVII Simposio Argentino de Paleobotánica y Palinología; 2018

Leaves of Pseudoctenis ornata (Cycadophyta) are chemically analyzed for the first Vme by semiquanVtaVve Fourier Transform Infrared (FTIR) spectroscopy. The FTIR-derived data are compared withthose obtained from Squamastrobus 0grensis leaves (Podocarpaceae). The specimens arecompressions with cuVcular features very well-preserved coming from the renowned Baqueró Group(ApVan, Santa Cruz, ArgenVna). Pseudoctenis ornata (BAPb 1217, 1220, 1222) was collected fromPunta del Barco FormaVon at Estancia El Verano locality, while S. 0grensis (BAPb 7678, 11321, 11324,11333, 11583-11586) comes from Anfiteatro de Ticó FormaVon at Bajo Tigre locality. The aim of thiscontribuVon is to reveal mesophyll and cuVcle chemical structures (funcVonal groups) of these twogymnosperm fossil taxa that underwent to volcanic se`ng influence. The spectrometric study wascarried out analyzing two sample forms: (1) compressions (including coalified mesophyll and cuVcle)and (2) cuVcles. The la)er were obtained from compressions by maceraVon. The FTIR-derived datawere staVcally evaluated by principal component analysis (PCA). In general, P. ornata has the highestaliphaVc nature. This is probably a consequence of micromorphological features (cuVcle thicknessand papillae) and cuVn composiVon (monomer types and their relaVve contents). On the other hand,S. 0grensis compressions show, in most samples, longer and straight aliphaVc chains than theirrespecVve cuVcles. These results are probably related to the fact that both fossil taxa are preservedas fossilized cuVcles (i.e., compressions having a certain degree of natural oxidaVon). This is mostlikely a)ributed to the intense volcanic acVvity and cold ash falling occurred during the ApVansedimentaVon in Patagonia.