Interpretación paleoambiental del Grupo Mandiyutí (Carbonífero Superior), provincia de Salta, Argentina. Evidencias palinológicas, sedimentológicas y tafonómicas

Abstract

In the Argentine region of Tarija Basin, the Mandiyutí Group includes two units: Escarpment and San Telmo Formations. The stratigraphic section, around 700 meters thick, is located at the surroundings of Caraparí River, Salta province. The paleornicrofloral study was made with samples from a section of 100 m thick at the boundary between these units. The recognition of more than one hundred of miospore species with their botanical affinities has allowed to reconstruct five paleofloral communities, each one with particular hydrophytic requirements. They have been defined as Paleocommunity A (lycophytes-sphenophytes), Paleocommunity B (filicophytes), Paleocomrnunity C (mainly monosaccate pollen grains), Paleocommunity D (poliplicate pollen grains), Paleocommunity E tBotrqococcus and other probable algae). Based on palynological. taphonornic and sedimentologic analyses from the studied section continental conditions are inferred. A trencl of evolution for the depocentre, starting with a lacustrine system under humid conditions that ends with a drier alluvial plain, has been established. This paleoclimatic change is suggested by the appearance of the Paleocornmunity D with Equisetosporites in the sample M445 of the middle section. It is also observed a change in the sediment color from grey in the lower and middle sections to red in the upper palynologically barren section. Finally, the observed transitional paleoclimatic evolution in this area of the Tarija Basin for the Carboniferous / Permian boundary is correlated with the same transitional change in other Argentine basins from this periodo