Gymnosperm pollen grains from the La Veteada Formation (Lopingian), Paganzo Basin, Argentina: biostratigraphic and palaeoecological implications

Abstract

This work forms the concluding part of a series of systematic studies of typical Gondwanan Permian palynofloras from the type section of the La Veteada Formation in the Paganzo Basin, central-western Argentina. It deals with the description and/or illustration of the non-taeniate monosaccate, bisaccate and polysaccate gymnosperm pollen species that are richly represented in the La Veteada Formation and are attributed to 25 genera. These taxa are allied to, or derived from, a diverse range pteridosperms (corystosperms, peltasperms), conifers (including Voltziales) and cordaites; Ginkgoales, Cycadales and Gnetales also have some representation. The new species, Jugasporites vellicoites, is instituted and the new combination, Alisporites angustus (Ouyang & Norris) comb. nov. et emend., is proposed. New evidence to support a Lopingian age for the palynoflora, considered to be the youngest Permian palynoflora recorded hitherto in South America, is based on a summary of the published information about its composition, together with an assessment of previous records of the diversity of gymnosperm taxa analysed in this contribution. The co-occurrence of several species of taeniate pollen (described in a previously published part of our work) and the gymnosperm taxa documented here, which have not been reported before from South America, differentiates the palynoflora of the upper La Veteada Formation from all others so far described from this continent. The high ratio of pollen versus spores, plus the botanical and palaeoecological inferences of the gymnospermous component of the formation’s palynoflora, reflects a parent vegetation adapted to relatively dry conditions. Such a low-humidity environment is consistent with the sedimentological evidence, which suggests that, through the Lopingian, semi-arid to arid climates dominated the southern South American basins.