Palynology of the Malanzan Formation (Upper Carboniferous), La Rioja Province, Argentina:: New data and paleoenvironmental considerations

A new palynological association from the middle part of the Malanzan Formation (Sierra de Los Llanos) is described. The microflora is composed of thirty species of spores and pollen grains associated to algae, prasinophyceaes and acritarchs. The most common species of spores are Retusotriletes anfractus Menendez and Azcuy, Apiculiretusispora ralla (Menendez and Azcuy) Menendez and Azcuy, A. variornata (Menendez and Azcuy) Menendez and Azcuy, Rugospora cortaderensis (Cesari and Limarino) nov, comb., Foveosporites hortonensis (Playford) Azcuy, Raistrickia rotunda Azcuy, Convolutispora muriornata Menendez, Granulatisporites varigranifer Menendez and Azcuy, Cristatisporites stellatus (Azcuy) nov, comb., C. menendezii (Menendez and Azcuy) Playford, Anapiculatisporites argentinensis Azcuy, and Pustulatisporites papillosus (Knox) Potonie and Kremp. According to the known stratigraphic distribution of these species, a Late Carboniferous age (late Namurian-Westphalian) is proposed for the Malanzan Formation. In addition, the presence of Navifusa variabilis nov. sp., Leiosphaeridia, Cymatiosphaera and Greinervillites suggests brackish conditions during at least part of the sedimentation of the Malanzan Formation. Probably, this evidence suggests a postglacial transgression (late Namurian-early Westphalian) that flooded lakes and fluvial valleys.