New paleofloristic elements and stratigraphic considerations for the Nestares Formation (Lower Jurassic, Argentina)

Abstract

In this contribution we describe new elements of the paleoflora of Nestares Formation in its type section, exposed along both banks of the Limay River, close to the Alicurá dam (southern margin of Neuquen Basin). Samples were collected from fossiliferous level AL 18 corresponding to black shales and mudstones, interpreted as overflow events from main fluvial channels, as well as avulsion events that cut the flood plain. Neocalamites suberosus Bomfleur, Escapa, Serbet, Taylor and Taylor, Equisetites patagonica Herbst, Todites cacereii Escapa and Cúneo, Osmundopsis rafaelli Escapa and Cúneo, Cladophlebis antarctica Halle, Goeppertella macroloba Herbst, Goeppertella neuqueniana Herbst, Goeppertella stipanicicii Herbst, Dictyophyllum sp., Dicroidium odontopteroides Gothan, Scleropteris grandis Artabe, Morel and Zamuner, and Cycadolepis lanceolata Menéndez are described for the first time for this unit. The presence of elements characteristic of Triassic floras, such as Dicroidium odontopteroides and Goeppertella stipanicicii illustrate the early Mesozoic affinity of the Nestares paleoflora. Stratigraphic relationships of Nestares Formation are analysed considering sedimentological and environmental features as well as paleobotanical content, and support a Sinemurian age for this unit.