A PRE-GLACIAL FLORAL BELT IN GONDWANA INDICATING WARM CLIMATE DURING THE LATE VISEAN (LATE EARLY CARBONIFEROUS)

Late Visean fossil floras from South America (Peru, Bolivia, Brazil), Africa (Niger), India, and Australia are distinctly different from both the earlier and later Carboniferous floras of Gondwana. Stratigraphic, palynologic, and isotope data allow assignment of these floras to a “middle” Carboniferous age (late Visean and earliest Serpukhovian). These floras are dominated by pteridosperm foliage (Nothorhacopteris, Triphyllopteris, Sphenopteridium, Diplothmema) and characterized by the occurrence of tree-lycopsids (Tomiodendron) and primitive shrubby sphenopsids (Archaeocalamites). The tree lycopsids represent a growth form that cannot survive periods of frost and the sphenopsids are known from the tropics. Thus, these floras represent a warm temperate, frost-free, floral belt in Gondwana that reached from as much as 30^o to 60^o South and existed directly before the onset of the major episode of the Carboniferous glaciation. The plants lived during an interval of very warm climate on Earth as indicated by the width and extent of the floral belt. The term Paraca floral belt, before restricted to the center-north South American floras, has been introduced in the literature to include all of these floras throughout Gondwana. An important paleofloristic implication is the establishment of the stratigraphic and compositional difference and connection between floras of the Paraca belt and the well-known Nothorhacopteris-Botrychiopsis-Ginkgophyllum Flora found in the Upper Carboniferous deposits of Argentina.