Diatom biostratigraphy and age of the Pliocene Sorsdal Formation, VestfoldHills, East Antarctica

Fossil marine diatom assemblages from the Sorsdal Formation, a deposit of d iatomaceous sand from Marine Plain in the Vestfold Hills, protide age and p alaeoenvironmental information from a Pliocene coastal setting in East Anta rctica. Benthic and meroplanktic diatom taxa suggest deposition in a shallo w coastal embayment with water depths of 20-25 m. Diatom biostratigraphy in dicates that the Sorsdal Formation belongs to the Fragilariopsis barronii Z one (4.5 to 4.1 Ma), through correlation to reference sections in the Ross Sea and Southern Ocean. Features of the other biota suggest higher sea-surf ace temperatures and reduced sea-ice cover, consistent with global records of higher sea level.