A new Serpukhovian (Mississippian) fossil flora from western Argentina: Paleoclimatic, paleobiogeographic and stratigraphic implications

An uppermost Mississippian (Serpukhovian) fossil flora from western Argentina is described for the first time. Its particular composition includes both, warm climate plants typical from the Pennsylvanian of Gondwana, namely pteridosperms, sphenophytes as well as arboreous lycopsids; and small lycopsids characteristic of cooler climates of pre-Serpukhovian times. A warm–temperate climate is inferred for this association, which fills a time gap between those Pennsylvanian and Mississippian classic floras previously known. The presence of Tomiodendron, Nothorhacopteris kellaybelenensis and Paracalamites allow the recognition of the Paraca Floral Realm in Argentina, supporting the existence of a nonglacial paleoclimate period, developed just before of the Bashkirian–Moscovian Gondwanan glaciation and after a latest Visean glaciation. It likewise would indicate the paleogeographic position of south west Gondwana, which would have acceded to a warm temperature latitudinal belt during Serpukhovian times. The recognition of this floral assemblage has relevant biostratigraphic and lithostratigraphic implications for the western margin of Gondwana. It defines a new zone for western Argentina, herein named Frenguellia eximia–Nothorhacopteris kellaybelenensis–Cordaicarpus cesarii (FNC) zone, which is recorded in the oldest known lithostratigraphic unit from the Paganzo Basin, the Loma de los Piojos Formation nom. nov.