Fossil pollen ans spore from the Southernmost Eocene sediments of South America, Rio Turbio Formation, Argentina

DAMIÁN ANDRÉS FERNÁNDEZ; VIVIANA D. BARREDA; LUIS PALAZZESI; MARÍA C. TELLERÍA

Mendoza

Congreso; 4th International Palaentological Congress; 2014

We present a diverse and well preserved palynological assemblage from the Río Turbio Formation, mid-late Eocene, SW Santa Cruz Province, Argentina. The region supports at the present time a low diverse southern beech forest dominated by Nothofagus antarctica (Forster) Oersted. The palynological assemblage preserved in the Río Turbio Formation includes marine and continental palynomorphs. Spores of fungi and ferns, together with pollen of angiosperms and gymnosperms, were abundant and diverse. Within fern families, Cyatheaceae/Dicksoniaceae/Schizaceae, Osmundaceae, and Gleicheniaceae were represented. Within angiosperms, pollen of Nothofagaceae (Nothofagiditesspp.), Myrtaceae (Myrtacidites spp.), and Proteaceae (Cranwellipollis sp., Propylipollis sp., Proteaciditessp.) were dominant in the assemblage. Pollen assigned to two pairs of phylogenetically unrelatedgenera (Nothofagus/Misodendrum and Prosopis/Tripodanthus) may trace back the host-parasite interaction between them to the Eocene. The gymnosperm record is dominated by Podocarpaceae, and specially, by pollen similar to extant Podocarpus (Podocarpidites rugulosus Romero, P. elegans Romero), Lagarostrobus (Lepidothamnus sp.) and Phyllocladus (Phyllocladidites mawsonii Couper). Overall, the spore/pollen assemblage includes more than 54 morphotypes (rarefied at a count of 300 specimens), suggesting a highly diverse paleoflora developed during mid-late Eocene times. This interval coincides with a period of pronounced global warming recorded at middle to high latitudesin both hemispheres. Fossil plants preserved in the Río Turbio Formation are represented today by groups confined to temperate and subtropical/tropical rainforest in lower latitudes of South America as Ilex (Ilexpollenites sp.), Cupania (Cupanieidites sp.), and members of the Malpighiaceae (Perisyncolporites pokornyi Germeraad, Hooping and Muller), Bombacaceae (Bombacacidites sp.), and Arecaceae (Arecipites sp., Mauritiidites sp.), together with typical taxa of dry, sclerophyll forests of nothern Argentina as Prosopis sp.