CONICET | Buscador de Institutos y Recursos Humanos

Paleobotanical and sedimentological studies on Piedra Clavada, Mata Amarilla and La Anita formations described floristic evolution during Middle-lower Upper Cretaceous in the Austral Basin, southwest Patagonia. Seven different fossiliferous levels in a continuous stratigraphic sequence containing plant compressions were intensively collected in ten localities. Four fern foliage were identified, two of them fertile (Matoniaceae and a probable Dennstaedtiaceae). Equisetites roots and stems were observed in the lowermost level. Additional material of Fitzroya tertiaria Berry preserving branches, filotaxis and cuticle discard Cupresaceae affinities although new charcoalified wood confirm the presence of this family. Taxodiaceae female cones and ovuliferous scales are present as well. Angiosperm leaves, flowers, fruits and in situ cuticle were recovered in all fossiliferous levels (including the lowermost Upper Albian ones) recognizing a fast Cenomanian radiation and dominance of dicots in littoral paleoenvironments, also recognized base on recent palinological studies. Based on these new records it is possible to reassign species published in 1928-1953 and describe new ones. Some historic collection containing angiosperm leaves that were erroneous placed in Mata Amarilla Formation are now recognized belonging to the uppermost section of Piedra Clavada Formation (Upper Albian). The floristic composition throughout these units shared several taxa with the coetaneous Kachaike Sandstones at species level that remarks possible biostratigraphic correlations and the need of floristic and stratigraphy differentiation in other areas of the basin. Absence of discordances between these lithologic units allows a detailed study of angiosperm diversification and dominance through all the lower Upper Cretaceous in Patagonia.