Palynology of El Foyel group (Paleogene), Ñirihuau basin, Argentina

Abstract

This work aims to analyze the paleovegetation, paleoclimates and paleoceanography of the Paleogene of the Río Foyel section (El Foyel Group), Ñirihuau Basin, Argentina. It comprises Troncoso, Salto del Macho and Río Foyel formations. Sporomorph analysis reflects a regional forest dominated by Nothofagaceae, Myrtaceae, Podocarpaceae and Palmae, developed under a temperate to warm-temperate and humid climate. In the studied section, the relation between terrestrial/marine palynomorphs is considered. In the Troncoso Formation, terrigenous palynomorphs dominate over marine elements. The recurrent presence of gymnosperm pollen with Araucariaceae indicates temperate and humid conditions. The Salto del Macho Formation shows a retraction of the gymnosperm forest, associated with the dominance of Nothofagus forest, indicating a temperate and humid condition. In the Río Foyel Formation, the sporomorphs indicate the presence of a temperate to warm-humid forest with subordinate open areas and a remarkable input from the coastal environment. In the same formation, the palynological characteristics, which indicate upward shallowing, allow the identification of parasequences. The bounding surfaces of parasequences are defined as surfaces of flooding which represent a relative sea level rise (marine flooding surfaces). The Río Foyel Formation shows an upward shallowing sequence, indicated by the decrease in abundance and diversity of dinocysts. Different marine flooding surfaces were detected, associated with the diversity and abundance of dinocyst. A comparison of these spore-pollen assemblages with others from Patagonia, using multivariate statistic techniques, yields strong similarities between the Troncoso Formation and the Sloggett Formation (late Eocene to?early Oligocene); and between Salto del Macho and Río Foyel formations with Loreto Formation (late Eocene-Oligocene) and San Julián Formation in cabo Curioso area (Oligocene). © 2012 by the Sociedade Brasileira de Paleontologia.