The plant community of the Apeleg Formation (Lower Cretaceous), Patagonia. Diversity and its comparison with coetaneous megafloras of Western Gondwana

CARRIZO MARTIN A.; LAFUENTE DIAZ, MAITEN A.; DEL FUEYO GEORGINA M.; CÁRDENAS ORLANDO

Congreso; XIV International Palynological Congress and X International Organisation of Palaeobotany Conference; 2016

The Lower Cretaceous has proved to be a period of great diversification and development of plant communities allacross Western Gondwana. This is demonstrated by the abundant plant fossils found in different litostratigraphicunits such as those of the Springhill, Anfiteatro de Ticó and Kachaike formations in Santa Cruz Province (Argentine),the Cerro Negro Formation in Antarctica and the Crato Formation in Brazil. However, other plant assemblagesare merely mentioned as part of old geological studies and stratigraphical works without a complete analysis oftheir floras, as it is the case of the megaflora from the Apeleg Formation (Hauterivian/Barremian) in the ChubutProvince of Argentine. This unit is part of the sedimentary sequence that comprises the region between theApeleg Village, the Alto Río Senguerr city and the Lago Fontana area in the Patagonian Cordillera. It is describedas deposits of transition from a marine to a continental paleoenvironment overlaying the Katterfeld Formationdeposits. The outcrops of the Apeleg Formation are typically composed by levels of dark grey massive sandstonesintercalated with layers of consolidated black lutites. The knowledge regarding the plant community compositionof this unit is very limited, only one paleobotany study was made with descriptions and illustrations of the florafound at the proximities of the Estancia Victoria locality and includes impressions of fronds of Scleropteris sp.,Cladophlebis sp., Taeniopteris dissecta Baldoni et De Vera, Ptilophyllum aff. antarcticum and Ptilophyllum sp.. Inthis work, fossil plants found in new fossiliferous deposits of the Apeleg Formation outcropping in the samelocality are described. The new materials consist of numerous impressions of fronds and branches that belongto Baiera (Braun) Florin (Ginkgoales), Brachyphyllum (Lindley et Hutton) Harrris, Elatocladus Halle (Coniferales)and bract-scale complex most probable attributable to Araucariaceae. These findings increment the diversityand richness of the Apeleg Formation megaflora. In comparison with other Lower Cretaceous plant communitiesmentioned above from Western Gondwana, the plant assemblage of the Apeleg Formation is the less diverse ofall. The intense volcanic activity and thermic metamorphism that is present in the entire sequence, may haveprobably affected the preservation of the original flora that inhabited the area during the Lower Cretaceous.Future studies of the deposits of the Apeleg Formation may reveal new and more varied flora. It is a contributionto grants ANPCyT PICT 2012/528 and CONICET PIP 112-201201-00212