Palinología de la Formación Malanzán (Carbonífero Superior), La Rioja, Argentina: nuevos datos y consideraciones paleoambientales

Abstract

A new palynologícal association from the middle part of the Malanzán 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 Retusotrileies anfracius Menéndez and Azcuy, Apiculiretusispora ralla (Menéndez and Azcuy) Menéndez and Azcuy, A. variornata (Menéndez and Azcuy) Menéndez and Azcuy, Rugospora cortaderensis (Césari and Limarino) nov. comb. Foveosporites hortonensis (Playford) Azcuy, Raistrickia rotunda Azcuy, Convolutispora muriornata Menéndez, Granulatisporites varigranifer Menéndez and Azcuy, Cristatisporites siellatus (Azcuy) nov. comb., C. menendezii (Menéndez and Azcuy) Playford, Anapiculatisporites argentinensis Azcuy, and Pustulatisporites papillosus (Knox) Potonié and Kremp. According to the known stratigraphic distribution of these species, a Late Carboniferous age (late Namurian-Westphalian) is proposed for the Malanzán 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 Malanzán Formation. Probably, this evidence suggests a postglacial transgression (late Namurian-early Westphalian) that flooded lakes and fluvial valleys.