Palynofloras from the Maastrichtian Chorrillo Formation (Patagonia, Argentina): Paleoenvironmental and paleoclimatic implications

Abstract

The uppermost Cretaceous continental Chorrillo Formation crops out in the southernmost regions of South America. This unit is characterized by a diverse array of fossil organisms, including continental invertebrates, vertebrates, palynomorphs, fossil woods and leaf impressions. In this work, a palynological study of samples the upper levels of this unit supports an upper Maastrichtian age (not reaching the K/Pg boundary). Quantitative palynological data incorporating all available information for the unit results in the recognition of five different floristic assemblages, which differ in variations in the proportion of taxa, without evidences of taxonomic replacements across the unit. An integrated analysis using palynological, sedimentological and paleosol data suggest that the moderate changes observed in the floristic composition and vegetation structure along the studied interval could be attributed to small changes in the humidity regime related to subtle variations in the precipitations regime, or different habitat preferences of the plants and their distribution in reference to the fluvial system.