LATE PLIOCENE DIATOMS IN A DIATOMITE FROM PRYDZ BAY, EAST ANTARCTICA

Very well-preserved Pliocene diatoms from a diatomite unit interbedded within glacial sediments at Ocean Drilling Program Site 742 in Prydz Bay, Antarctica are documented and illustrated. The presence of Thalas siosira kolbei, T. torokina, Actinocyclus actinochilus, A. karstenii a nd the absence of Nitzschia interfrigidaria. T. insigna and T. vulnifi ca in Sample 119-742A-15R-4, 44-46cm constrain its age to ca. 2.2-1.8 Ma (late Pliocene). Diatoms associated with sea ice constitute 35% of the Pliocene diatom assemblage, compared with 71% of the modem sedimen t assemblage at the site, suggesting that sea ice was present during t he late Pliocene period of deposition of the sample, although it proba bly was not the significant feature it is today. Thalassiosira ellitip ora (Donahue) Fenner is described and illustrated in detail and is val idly published. An expanded description and numerous illustrations are also presented for T. torokina Brady.