The Jurassic Flora of Nestares Formation , Neuquen Basin, Argentina

COTUREL, ELIANA P.; SAGASTI, ANA J.; MOREL, EDUARDO M.

Paris

Congreso; 5th International Paleontological Congress; 2018

Palaeofloristic assemblages from the Jurassic were shaped by the Late Triassic extinction,which led to the loss of dominance of the corystosperms in Gondwana, and the replacement of the floristic components in this region. During the Jurassic Period, Southern South America was in a warm temperate biome. Early Jurassic oras from Argentina were dominated by conifers, bennettitaleans and ferns in a relatively homogeneousora, described from Mendoza to Antarctica. The Neuquen Basin developed from the Jurassic to the Early Cretaceous as one of the major sedimentological basins of the Mesozoic of Argentina, with economic importance by the exploitation of hydrocarbons. The Nestares Formation is on the southern margin of the Neuquen Basin. The age of the Nestares Formation is in dispute between the megafloristic and palynological records, with a Sinemurian age proposed by biostratigraphic correlation with other local, dated units, against a Toarcian age based in the development of the dino agellates. In this contribution we report for the rst time for the Nestares Formation several fossil plants. We add Cycadolepis Saporta, Cladophlebis antarctica Halle, Dicroidium Gothan, Komlopteris Barbacka, Pagiophyllum Heer, Taeniopteris Brongniart, and Nododendron Artabe and Zamuner, to the previously described ora. The material is preserved as compressions with a good preservation of cuticles, which allow us to study the stomatal density of the conifer and bennettitaleans leaves, leading us to add information to the global studies about paleoclimates in this period. These descriptions result also in a more up-to-date palaeobiological knowledge of the present paleo floristic elements, and a better paleoecological characterization of the unit. The presence of taxa related to the older Triassic oras such as Dicroidium support the Lower Jurassic age of the Nestares Formation, but for the moment the oristic record does not resolve by itself the age dispute. Likewise, the floristic similarities between the Lower Jurassic floras of Argentina and Antarctica are rearmed.