Andrzej GAZDZICKI POLISH POLAR STUDIES Institute of Paleobiology XXVI Polar Symposium Polish Academy of Sciences Twarda 51/55, OO-SIS'Warsaw POLAND Lublin, June 1999

EOCENE OF SEYMOUR ISLAND, EO CEŃ SKI EKOSYSTEM WYSPY SEYMOUR, ANTARKTYKA

ABSTRACT

The Seymour Island explored by the Swedish South Polar Expedition at the beginning of this century has proved to be one of the key localities in Antarcti- ca. The first documented from Antarctica were collected from this small remote island in December 1892 during the voyage of the Norwegian whaling ship Jason headed by Captain C.A. Larsen. The stratigraphic marine sequence on the island extends from the Upper Cretaceous Lopez de Bertodano Formation through the Sobral, Wiman and Cross Valley formations to the La Mese- ta Formation. Over 900 species of micro- and macrofossils have been described from this island, and out of these more than 200 are new to science. The , exposed in the north-eastern part of Seymour Island represents about 800 m of nearshore sandstones and siltstones, which preserve an exceptional record of the Eocene-?earliest Oligocene life. Throughout the forma- tion microfossils (palynomorphs, diatoms, foraminifers, ostracods), invertebrates (corals, molluscs, crabs, bryozoans, brachiopods, in a number of fossiliferous hori- zons. Many representatives of the above groups have the first fossil record in the La Meseta Formation. Paleoecological associations with diverse fossil assemblages indicate a tempe- rate marine environment for the La Meseta Formation. Paleobotanical studies sug- gest that the terrestrial paleoenvironment during the Eocene was heavily vegeta- ted (Nothofagus-podocarp forest) and had a humid, temperate or cold-temperate climate similar to present-day southern South America. The results of geochemical analyses made on the fossil shell material from the La Meseta Formation suggest a considerable climatic cooling event at the time period of deposition of the upper part of the formation. This cooling event may be correlated with the first phase of the late Eocene-early Oligocene continental glaciation in Antarctica. These data 66 Andrzej Gaździcki are important in providing information on the La Meseta Formation biota paleo- environment changes in time and space. The La Meseta Formation biota assemblages indicate favourable conditions for life in shallow marine and terrestrial realms during the final stage of the Gondwa- naland breakup and onset of the Paleogene continental glaciation in the sector.