This paper reports on the biostratigraphic, paleobiogeographic and paleoecologic aspects of palynoflora recovered from sedimentary rocks preliminarily assigned to the Lago Colhué Huapi Formation, in the Golfo San Jorge Basin. The present palynological assemblage includes Maastrichtian marker species of the austral Proteacidites/Nothofagidites Province such as Quadraplanus brossus and Tubulifloridites lilliei. Typical species of the Maastrichtian paleotropical Palmae Province, Buttinia andreevi and Gabonisporis vigourouxii, are also recognized in the palynoflora. These facts indicate the mixed character of the paleoflora and the prevalence of transitional climatic conditions at the paleolatitude of the Chubut Province in the uppermost Cretaceous. The palynoflora composition suggests the local existence of a warm and low energy freshwater body.