NOTHOFAGIDITES ERDTMAN EX POTONIE IN THE PALEOGENE OF KING-GEORGE ISLAND, ANTARCTICA

Nothofagidites (fusca and brassii) were found in the Palaeogene of Kin g George Island (South Shetland Islands). They are associated with a r ich palynoflora composed of many ferns, Podocarpaceae, Araucariaceae, Proteaceae and Gunneraceae. A comparative study of extant and fossil p ollen grains (optical microscope and SEM) allowed the establishment of some botanical affinities with South American species to be establish ed. Nevertheless the Nothofagidites of King George Island have an exin e with strong spines, a characteristic of some species of the brassii group living in New Guinea and New Caledonia under a warm and humid cl imate. According to these data, and those based on the study of fossil woods from the same sites, it appears that, during Palaeogene, the fo ssil southern beech (Nothofagus) were trees of warm and humide climate with alternation of dry and wet seasons. These trees were growing tog ether with plants now living under a subtropical climate. During glaci al periods and through the volcanic and tectonic events of the late Pa leogene, at least some Nothofagus species migrated, became adapted to the climatic changes and live today in the Southern Hemisphere cold te mperate forests, particularly in southern Chile. So the sole presence of Nothofagus in the Tertiary sediments cannot be used as a criterion for the existence of a cold temperate climate as it is often argued.