【Title】PRELIMINARY STUDY ON THE SPORE-POLLEN ASSEMBLAGES FOUND IN THE CENOZOIC SEDIMENTARY ROCKS IN GROVE MOUNTAINS, EAST ANTARCTICA
Cenozoic sedimentary rocks;
【Abstract】Glacigenic sedimentary rocks were collected from modern tills of the Grove Mountains, East Antarctica during the 1998-1999 Chinese National Antarctic Research Expedition. These sedimentary rocks are correlated with Cenozoic sedimentary strata of the Pagodroma Group in the neighboring Prince Charles Mountains and the Sφrsdal Formation in Vestfold Hills based on their lithilogic and sedimentary features. Sedimentary clasts contain sparsely Late Tertiary spores and pollens, including: Toroisporis ( Lygodiaceae ) , Osmunda , Granulatispontes ( Pteridaceae?) , Polypodiaceae, Podocarpus , Araucardiaceae, Artemisia, Chenopodiaceae, Rhus , Nothofagidites ( Nothofagus ) , Proteacidites ( Proteaceae ) , Quercus , Fraxinoipollenites ( Oleaceae ) , Oleoidearumpollenites(Oleaceae) , Operculumpollis, and Tricolpopollenites. Most pollen and spores should be of local sources according to their preservation conditions as well as correlations with the diatom assemblages found in the neighboring areas. The majority of the pollen assemblages, as represented by Podocarpus and Nothofagus, belong to the Weddellian biogeocenose. However, some exotic components from the basement sedimentary rocks may have been included during erosion of the proximal ice sheet. If the source areas of glacigenic sedimentary rocks that bear the pollen and spores are assumed to be local, or in the up glacier areas, the pollen assemblages in these samples might represent an inland flora during a warmer period of the ice-sheet evolutionary history. The existing of Artemisia and Chenopodiaceae implies that the pollen assemblages may of the Late Tertiary (most probably Pliocene) age. The absence of diatoms in the samples analyzed may indicate that there are no Cenozoic marine strata in the interior of the East Antarctica beyond the Grove Mountains. The existing of Nothofagus in these pollen assemblages is significant because Nothofagus pollen grains have been discovered also from the Sirius Group and other strata outcropped in Antarctica,and thus bear implication of sedimentary age,phytogeography,and ecological conditions. As a preliminary conclusion, we think that the existence of the Cenozoic glacigenic rocks and their pollen assemblages present new evidence for a large scale glacial retreat event in Grove Mountains of East Antarctica, and thus support a dynamic East Antarctic Ice Sheet (EAIS) . This is consistent with the interpretations of Webb and Harwood (1984) .