First palynoflora for the Permian La Golondrina Formation (Santa Cruz Province, Argentina): biostratigraphic and paleoenvironmental implications for the Dos Hermanos Member

Abstract

We present the first integrated study of the microflora and its associated megaflora from the upper member of the La Golondrina Formation (Dos Hermanos Member) in the La Golondrina Basin, Santa Cruz, Patagonia, Argentina. The microflora is dominated by striate bisaccate pollen (Guttulapollenites, Striatopodocarpites), non-striate bisaccate pollen (Scheuringipollenites, Alisporites/Falcisporites, Platysaccus), trilete spores (Verrucosisporites/Convolutispora, Punctatisporites), and sulcate-plicate pollen (Weylandites). Cluster analysis based on species distribution shows a close affinity with the microflora from the Emakwezini Formation in the Lebombo Basin, South Africa. This correlation supports a Lopingian age for the Dos Hermanos Member, concurring with recent radiometric dating of the unit. The palynological assemblage of the Dos Hermanos Member is consistent with the associated megaflora, which comprises mostly glossopterids and true ferns, alongside sphenophytes and scarce conifers. Both mega- and microfloristic evidence suggest that the flora of the Dos Hermanos Member developed along the margins of the water bodies (lakes, swamps, and marshes) within the floodplains of a low-sinuosity braided river system. The forest was dominated by arborescent Glossopteridales, with an herbaceous-shrub undergrowth composed of true ferns, sphenophytes, lycophytes, and bryophytes. Conifers and seed ferns (other than Glossopteridales), which are scarce or absent in the megaflora but constitute major elements of the palynoflora, likely inhabited the uplands near the deposition area.