EVIDENCE OF PLIOCENE NOTHOFAGUS IN ANTARCTICA FROM PLIOCENE MARINE SEDIMENTARY DEPOSITS (DSDP SITE 274)

Microfossil assemblages in Pliocene sediments from DSDP Site 274 (68 d egrees 59.81'S, 173 degrees 25.64'E) provide data on the age of the se diments and suggest the presence of Norhofagus (southern beech) in Ant arctica during the Pliocene. A suite of 17 samples was collected in an interval from Samples 28-274-6R-1, 83-87 cm to 28-274-11R-4, 73-77 cm (48.33-100.29 mbsf). Biostratigraphic study of the abundant diatom as semblages combined with published radiolarian data indicates that the sample interval ranges in age from 5.0 to 2.2 Ma, with an apparent unc onformity between about 3.8 and 3.2 Ma. Nothofagidites (the genus for fossil pollen referable to Nothofagus) occurs throughout the interval, as well as pollen and spores with known stratigraphic ranges that une quivocally indicate reworking from older rocks. Species of Nothofagidi tes recovered include N. asperus, N. brachyspinulosus, N. flemingii, N . senectus, and N. sp. cf. N. lachlamiae; the latter form is previousl y known from the Sirius Group in the Transantarctic Mountains. Abundan t palynomorphs were recovered in only three of the samples from Site 2 74 (Samples 28-274-9R-2, 15-19 cm; 28-274-9R-2, 48-52 cm; and 28-274-9 R-2, 65-69 cm). Based on the diatom and radiolarian biostratigraphic d ata, the ages of these samples range from 3.00 to 3.01 Ma. The relativ e abundance of N. sp. cf. N. lachlaniae in the three samples is an ord er of magnitude higher than relative abundances for the other species of Nothofagidites in the same samples. The significantly higher relati ve abundance of N. sp. cf. N. lachlaniae suggests that this pollen was derived from trees of Norhofagus that were living in Antarctica durin g the mid Pliocene. Diatom assemblages from these three samples indica te that sediments in this interval were rapidly deposited as biogenic oozes in an open-ocean setting relatively free of sea ice, thus decrea sing the possibility of reworking from a single source bed rich in N. sp. cf. N. lachlaniae. Clearly, more detailed work in additional well- dated cores from around Antarctica is needed before a clear picture of the Neogene history of Antarctic terrestrial vegetation emerges.