Two new clavate Fragilariopsis and one new Rouxia diatom species with biostratigraphic and paleoenvironmental applications for the Pliocene-Pleistocene, East Antarctica

Abstract. Three new pennate diatom taxa, Fragilariopsis clava sp. nov. Duke; Fragilariopsis armandae sp. nov. Frazer, Duke et Riesselman; and Rouxia raggattensis sp. nov. Duke et Riesselman, are described and named from Pliocene-Pleistocene sediments collected from the continental rise adjacent to the Wilkes Land coast of East Antarctica. The stratigraphic occurrence of F. clava and F. armandae at IODP Site U1361 are well-constrained to Marine Isotope Stages G9-G7 (2.76–2.74 Ma) and 101–97 (2.58–2.47 Ma), respectively. The short stratigraphic ranges of F. clava and F. armandae are potentially useful biostratigraphic markers for constraining the age of late Pliocene to Early Pleistocene Antarctic sediments. Rouxia raggattensis is observed in the oldest sample examined at Site U1361 from ∼4.05 Ma and is more common between 3.0–2.15 Ma. The rise in abundance of R. raggattensis corresponds to a large turnover in diatom species between 3 and 2 Ma associated with Antarctic cooling, suggesting that sea surface conditions were favorable for R. raggattensis during this dynamic time. Clavate Fragilariopsis species diversified between 2.9–2.7 Ma, but some species quickly went extinct between 2.7–2.5 Ma, possibly because they were marginalized by the cooler climate conditions.