PALAEOFLORISTIC ANALYSIS OF THE RIO GUILLERMO FORMATION (LATE EOCENE–EARLY OLIGOCENE?), SANTA CRUZ, ARGENTINA

Abstract

Macrofloristic Paleogene units of southernmost Patagonia have few palaeobotanical studies. In this paper a new fossil leaf collection recovered from the Río Guillermo Formation (late Eocene–early Oligocene?) is analyzed. The palaeobotanical analysis reveals the presence of 10 fossil species, most of them related to Nothofagus Blume (Nothofagaceae), being the specimens of “Myrcia” bagualensis (Myrtaceae) the most abundant in the collection. Specimens referred to the families Rosaceae, Anacardiaceae, Lauraceae and Fagaceae were also recognized. The palaeofloristic assemblage from the Río Guillermo Formation is dominated by cold temperate taxa suggesting the presence of subantarctic paleofloras in this area. The great similarities between the Río Guillermo flora and that of the Oligocene Loreto Formation, coupled with the palaeoclimatic inferences, might indicate a younger age than previously suggested for the Río Guillermo Formation.